Dissertations / Theses on the topic 'Electrical impedance spectroscopy'
To see the other types of publications on this topic, follow the link: Electrical impedance spectroscopy.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Electrical impedance spectroscopy.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Foley, John J. "Microfluidic Electrical Impedance Spectroscopy." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1950.
Full textAbstract:
The goal of this study is to design and manufacture a microfluidic device capable of measuring changes in impedance valuesof microfluidic cell cultures. Tocharacterize this, an interdigitated array of electrodes was patterned over glass, where it was then bonded to a series of fluidic networks created in PDMS via soft lithography. The device measured ethanol impedance initially to show that values remain consistent over time. Impedance values of water and 1% wt. saltwater were compared to show that the device is able to detect changes in impedance, with up to a 60% reduction in electrical impedance in saltwater. Cells were introduced into the device, where changes in impedance were seen across multiple frequencies, indicating that the device is capable of detecting the presence of biologic elements within a system. Cell measurements were performed using NIH-3T3 fibroblasts.
2
Sánchez, Terrones Benjamín. "Broadband electrical impedance spectroscopy for dynamic electrical bio-impedance characterization." Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/132281.
Full textAbstract:
The electrical impedance of biological samples is known in the literature as Electrical Bioimpedance (EBI). The Electrical Bioimpedance enables to characterize physiological conditions and events that are interesting for physiological research and medical diagnosis. Although the Electrical Bioimpedance weakness is that it depends on many physiological parameters, on the other hand, it is suitable for many medical applications where minimally invasive and real-time measurements with simple and practical implementations are needed.
The Electrical Impedance Spectroscopy (EIS) techniques based on broadband excitations are expected to help to understand various unsolved problems in biomedical applications. Broadband EIS opens up the possibility to reduce drastically the measuring time for acquiring EBI time-variations but, at the same time, measuring in a short time compromises the EBI accuracy. The way to overcome this intrinsic loss of accuracy relies on the design of the appropriate time/frequency input excitation properties and the use of the suitable spectral analysis processing techniques.
The presented thesis covers the topics related to study of broadband excitations for Impedance Spectroscopy in biomedical applications and, more specific, the influence of the multisine excitation time/frequency properties on the impedance spectrum accuracy and its optimization. Furthermore, an advanced fast signal processing method has been implemented to process in real-time EBI data corrupted by transients, a common situation when measuring in a short measuring time. Despite being the goal to apply all this knowledge for myocardial tissue regeneration monitoring, at the moment of drafting the thesis, any of the research projects that have supported this thesis have issued functional beating tissue. For that reason, the theory presented has been validated by a set of experimental measurements over animals and patients where the impedance spectrum time-varying properties were pretended to be characterized.
The thesis presents novel findings of relevance of a successful application of broadband EIS in two different measurement campaigns where it has been put in practice: (1) within the collaboration of the pneumology and cardiology service from Hospital Santa Creu i Sant Pau for in-vivo human lung tissue characterization, and (2), within the measurement of animal healthy myocardium tissue electrical impedance including its dynamic behavior during the cardiac cycle.
3
Molckovsky, Andrea. "Monitoring photodynamic therapy with electrical impedance spectroscopy." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0021/MQ54094.pdf.
Full text
4
Liu, Xing, and s3072856@student rmit edu au. "Electrical Impedance Spectroscopy Applied in Plant Physiology Studies." RMIT University. Electrical and Computer Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080428.092529.
Full textAbstract:
Electrical Impedance Spectroscopy (EIS) is a relatively new method applied to food quality assessment. EIS allows relatively inexpensive assessment, is fast, easy to operate and non-invasive. It has been adopted for investigation of fundamental electrical properties of plant tissues. Although the applications of EIS for food quality determination have been reported previously, the analytical relationships between electrical impedance properties and quality criteria have not yet been fully developed. Further exploration is thus important in acquiring more data on electrical impedance characteristics of fruits and vegetables and researching new approaches for determination of their quality. This dissertation aims to investigate the electrical impedance properties of fruits and vegetables, and explore the relationship between impedance and quality criteria. In particular, the present dissertation outlines experimental research conducted on relationships between impedance properties and fruit tastes as well as the impedance changes observed during ripening process. Impedance measurement to monitor moisture content changes in the progress of drying is also included in this research. In summary, the impedance properties have merits in fruits and vegetables quality assessment. The current used subjective visual inspection and assessment could be replaced by the EIS based approach as it is a more precise measurement of food quality. Further study is required to give this method practical value.
5
Nguyen, Son Thanh. "The effects of skin moisturizers using electrical impedance spectroscopy." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/32129/.
Full textAbstract:
Skin Electrical Impedance Spectroscopy (EIS) is a method that involves the injection of an AC current into human tissue and measurement of the resulting voltage drop. By measuring the tissue over a range of frequencies, the impedance spectrum can then be used to detect changes in the underlying nature of the skin tissue. One potential application is in monitoring the effects of over the counter products such as skin moisturisers on human skin. This can be useful for cosmetics companies in new product development where users of the cosmetic product could use such a device in their own home. A low cost, portable, custom-made bio-impedance analyser based on a four-point probe sensor has been constructed for measuring the skin impedance over short and long time periods. Long term measurements are motivated by manufacturer claims that the effects of moisturisers last up to 24 hours and hence a custom made device has been developed to carry out long term monitoring. The system is based around a dsPIC33F board that contains a DSP processor, Analogue Frontend and analogue stimulus all connected to a 4-point probe sensor. 100µA AC current (according to Medical Standard 60601-1) is passed to the skin through two outer probes and a voltage drop measured across the two inner probes. A DSP controls the analogue frontend, processes the measured data and transfers data to a PC for real time display. The portable custom-made device is validated against a Solartron 1260 + 1294 impedance analyser and achieved a within 5% error. Four different commercial skin creams: Bio-oil, Nivea, Palmer’s Olive Butter and Cocoa Butter have been investigated. Under controlled environmental conditions, four kinds of cream were applied to an allocated area of the arm for 1 minute. The EIS was then measured for up to 5 hours on these regions by the four point probe sensors captured by the custom-made device. Nivea, Cocoa Butter and Olive Butter have a similar response as they are type II humectants which attract water from deeper dermis to the stratum corneum. Bio oil however, can be classified as a type I occlusives as it blocked water vaporized from stratum corneum. The Impedance results can discriminate between Bio-oil/ Bare skin (Type I) and the other three Type II moisturizers (Nivea, Olive and Cocoa). This discrimination is appointed in two clear features: firstly, the impedance values from the type II creams have a much reduced variability when compared to the bare skin and Bio-oil; secondly, the plots of R versus X showed for the Type II creams to have a non “constant phase element” dominance whilst bare skin and Bio-oil showed no such behavior. Phase results demonstrated additional capacitance effects of Bio oil compared to other moisturizers. Simulation models are provided to compare with these practical results with the model fitting process.
6
Lue, Liqin. "Aspects of an electrical impedance tomography spectroscopy (EITS) system." Thesis, University of Sheffield, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.481744.
Full text
7
Keshtkar, Ahmad. "Characterisation of human bladder urothelium using electrical impedance spectroscopy." Thesis, University of Sheffield, 2004. http://etheses.whiterose.ac.uk/15164/.
Full textAbstract:
Bladder cancer is the most common malignancy in elderly people. In developed countries most bladder cancers are transitional cell carcinomas (TCC). This is a cancer of the urothelium (a transitional epithelium lining the bladder). In the UK there are approximately 13,000 new cases and 5400 deaths per annum (Black, Bray et al. 1997). Carcinoma in situ (CIS) is an early case of the invasive cancer, which is flat, nonpapillary and difficult to detect precisely by using common methods. It is an aggressive form of TCC which may progress to muscle invasive cancer. Bladder pathology is usually investigated visually by cystoscopy. Erythematous areas of the urothelium are usually observed but these can represent different conditions ranging from simple inflammation to flat CIS. CIS cannot be differentiated visually from other erythematous tissues. Biopsies must be taken from the suspect area to obtain diagnostic information. The selection of biopsy sites depends on simple visual inspection thus is effectively random, and can be negative in up to 90% of the patients (van der Meijden, Oosterlinck et al. 1999). This is a relatively high cost procedure in terms of both time and money and is associated with discomfort for the patient and morbidity. Electrical impedance spectroscopy (EIS) is a non-invasive screenIng technique to separate malignant areas from non-malignant areas in the urinary bladder. This is a result of the electrical impedance spectrum of the tissue being a function of tissue structure at the cellular level. The feasibility of adapting this minimally invasive technique to screen for bladder cancer, CIS during cystoscopy has been explored and compared with histopathological evaluation of urinary bladder lesions, both ex vivo and in vivo. Finite element modelling technique have been used to explore the relationship between urothelial morphology and the impedance spectrum. Both measured and modelled results showed that this technique is able to separate benign and malignant bladder tissue groups and the in vivo measurements suggest that classification of individual measurements should be possible.
8
Yaremyk, R. Ya. "DSP-Based Information-Measuring Microdevice for Electrical Impedance Spectroscopy Analysis." Thesis, Sumy State University, 2016. http://essuir.sumdu.edu.ua/handle/123456789/47278.
Full text
9
Ma, Hongshen 1978. "Electrochemical Impedance Spectroscopy using adjustable nanometer-gap electrodes." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42240.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (p. 151-154).
Electrochemical Impedance Spectroscopy (EIS) is a simple yet powerful chemical analysis technique for measuring the electrical permittivity and conductivity of liquids and gases. Presently, the limiting factor for using EIS as a portable chemical detection technology is the lack of absolute accuracy stemming from uncertainties in the geometrical factor used to convert measurable quantities of capacitance and conductance into the intrinsic parameters of permittivity and conductivity. The value of this geometrical conversion factor can be difficult to predict since it is easily affected by fringing electric fields, manufacturing variations, and surface chemistry. Existing impedance test cells typically address this problem using a calibration liquid with known permittivity and conductivity, however, this correction is not feasible in many applications since the calibration liquid may irreversibly contaminate the test electrodes. This thesis presents a technique for accurately measuring the permittivity and conductivity of liquids and gases without requiring the use of calibration liquids. This technique is made possible by precisely controlling the separation between two spherical electrodes to measure capacitance and conductance of the sample medium as a function of electrode separation. By leveraging the geometrical accuracy of the spherical electrodes and precise control of the electrode separation, the permittivity and conductivity of the sample can be determined without wet calibration. The electrode separation is adjusted using a flexure stage and a servomechanical actuator, which enables control the electrode separation with 0.25 nm resolution over a range of 50 gm. The nanometer smooth surfaces of the spherical electrodes also enable electrode gaps of less than 20 nm to be created.
(cont.) The technique for measuring permittivity and conductivity presented in this thesis could eventually be adapted to make miniaturized disposable impedance test cells for chemical analysis. Such systems could take advantage of conductivity assays to determine the presence and concentration of specific substances. The adjustable nanometer electrode gap can also be used to study the properties of chemical and biological systems in highly confined states. These studies are fundamentally important for understanding biochemical processes in natural systems where reactions often take place inside confined structures such as cells, organelles, and the intercellular matrix.
by Hongshen Ma.
Ph.D.
10
Ha, Sungjae. "A malaria diagnostic system based on electric impedance spectroscopy." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66030.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 69-71).
Malaria caused by Plasmodium falciparum infection is one of the major threats to world health and especially to the community without proper medical care. New approach to cost-efficient, portable, miniaturized diagnostic kit is needed. This work explores electric impedance spectroscopy (EIS) on a microfluidic device as a means of malaria diagnosis. This work introduces a microfabricated probe with microfluidic channel, and a high speed impedance analyzer circuit board. Combination of microfluidic device and circuit board resulted in a small-sized EIS system for micro-particles such as human red blood cell (RBC). After invasion by the parasites, RBC undergoes physiological changes including electrical property of cytoplasm and membrane. Detection of infected RBC is demonstrated as well as differentiation of micro-beads by surface charge density using EIS-based diagnostic system. Diagnosis based on EIS has merits over other diagnostic methods since it is label-free and quantitative test and applicable to whole blood, and also the test does not need bulky optical and electrical equipments.
by Sungjae Ha.
S.M.
11
Tšoeu, Mohohlo Samuel. "Electrical Impedance Tomography/Spectroscopy (EITS): a Code Division Multiplexed (CDM) approach." Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/22866.
Full textAbstract:
Electrical Impedance Tomography and Spectroscopy (EITS) is a noninvasive imaging technique that creates images of cross-sections "tomos" of objects by discriminating them based on their electrical impedance. This thesis investigated and successfully confirmed the use of Code Division Multiplexing (CDM) using Gold codes in Electrical Impedance Tomography and Spectroscopy. The results obtained showed 3.5% and 6.2% errors in determining the position and size of imaged anomalies respectively, with attainable imaging speed of 462 frames/second. These results are better, compared to those reported when using Time Division Multiplexing (TDM) and Frequency Division Multiplexing (FDM).This new approach provides a more robust mode of EITS for fast changing dynamic systems by eliminating temporal data inconsistencies. Furthermore, it enables robust use of frequency difference imaging and spectroscopy in EITS by eliminating frequency data inconsistencies. In this method of imaging, electric current patterns are safely injected into the imaged object by a set of electrodes arranged in a single plane on the objects surface, for 2-Dimensional (2D) imaging. For 3-Dimensional (3D) imaging, more electrode planes are used on the objects surface. The injected currents result in measurable voltages on the objects surface. Such voltages are measured, and together with the input currents, and a Finite Element Model (FEM) of the object, used to reconstruct an impedance image of the cross-sectional contents of the imaged object. The reconstruction process involves the numerical solutions of the forward problem; using Finite Element solvers and the resulting ill-posed inverse problem using iterative Optimization or Computational Intelligence methods. This method has applications mainly in the Biomedical imaging and Process monitoring fields. The primary interests of the author are, in imaging and diagnosis of cancer, neonatal pneumonia and neurological disorders which are leading causes of death in Africa and world-wide.
12
Burtone, Lorenzo. "Electrical Characterization of Organic Devices and Solar Cells by Impedance Spectroscopy." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-146467.
Full textAbstract:
In this work, the capacitive response of organic electronic devices is analysed. Particular attention is given to small-molecule organic solar cells, with the purpose of deriving an equivalent circuit for the small-signal response of these devices. The different components characterising the solar cells electrical response are individuated and discussed and a specific physical meaning is associated with each element of the equivalent circuit.
In the experimental section, the capacitive elements of the equivalent circuit are characterised by analysing organic diodes and solar cells. It is found that the capacitance of an organic solar cell is a combination of four components: the dielectric response of the materials, the depletion regions formed at the interfaces, the accumulation of free and trapped charge carriers.
The depletion regions formed in organic doped semiconductors are characterised by analysing organic p/n homojunction diodes composed of Zinc-Phtalocyanine (ZnPc). The results demonstrate that the mechanisms involved in the formation of depletion zones in organic semiconductors can be described by the classical Mott-Schottky theory. This allows to estimate the free charge carrier density of doped layers with capacitance measurements. In addition, the current-voltage characteristics of organic p/n homojunctions are found not to obey the classical Shockley theory.
It is demonstrated that charge carrier tunnelling is the cause of this discrepancy and an analytic model is used to describe the current-voltage characteristics. The accumulation of free charge carriers is found to induce capacitance effects typical of relaxation semiconductors. In presence of unbalanced charge carriers injection, negative capacitance values are observed.
It is shown that in different organic semiconductor devices, the injection of minority charge carriers induces a depletion in the majority concentration, resulting in a negative value of the accumulation capacitance.
Finally, the capacitance associated to trap states in ZnPc:C60 organic solar cells is analysed. The spatial position and occupation mechanisms of the traps are estimated. The trapping mechanism in small-molecule organic solar cells is clarified and the energetic distribution of these trap states is estimated being a Gaussian function with 55 meV width, a density of 3.5 × 1016 cm−3 and centred 0.458 eV below the electron transport level. Trap states are also found to act as recombination centres, limiting the efficiency of organic solar cells.
13
Jouravleva, Svetlana. "Dielectric relaxation time spectroscopy for tissue characterisation." Thesis, Oxford Brookes University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364927.
Full text
14
Bannwarth, Sebastian [Verfasser]. "Characterization of Membranes and Membrane Processes by Electrical Impedance Spectroscopy / Sebastian Bannwarth." Aachen : Shaker, 2017. http://d-nb.info/113817842X/34.
Full text
15
Anil, Kumar R. "Measurement Of Solar Cell AC Parameters Using Impedance Spectroscopy." Thesis, Indian Institute of Science, 2000. https://etd.iisc.ac.in/handle/2005/203.
Full textAbstract:
Photovoltaic (PV) conversion of solar energy appears to be one of the most promising ways of meeting the increasing future energy demand. In space, photovoltaic power source is the only alternative. The demand for higher power has necessitated the use of high speed switching charge controller and power conditioner. To design an efficient and reliable switching charge controller, the static (I-V) and dynamic (AC) characteristics of a solar cell need to be understood.
The AC parameters of a solar cell can be measured either by Frequency Domain technique or by Time Domain technique. In frequency domain technique, a small signal is applied about the operating point and the AC parameters are measured. Hence, in the frequency domain technique the steady state values of AC parameters at a particular operating condition are measured. In time domain technique, a transient measurement is made where the cell voltage varies from short-circuit to open circuit or vice versa. Hence, this technique gives only the time constant of a solar cell.
The impedance spectroscopy is a frequency domain technique widely used in electro chemistry to study battery characteristics. In the present investigation, the impedance spectroscopy is proposed for measuring the AC parameters of solar cells. An experimental set-up has been developed to measure the solar cell AC parameters.
The AC parameters of Silicon (BSR and BSFR) solar cells and GaAs/Ge solar cells are measured using impedance spectroscopy (IS). The cell capacitance, the parallel resistance and the series resistance are measured and compared. GaAs/Ge solar cell has shown only transition Capacitance throughout its operating range while silicon (BSR and BSFR) solar cells exhibited both transition and diffusion capacitances. Theoretical and experimental values of the cell parallel resistance are compared and are in good agreement. While the diode factor in silicon solar cell varies from 2 to 1, where as in GaAs/Ge solar cell it varies from 4 to 2 to 1. Measurements conducted using open circuit voltage buildup (time domain technique) on silicon BSR solar cell shows that the collected data can be used for the restricted purpose of measuring cell transient response. The dime domain technique could not estimate the solar cell.
It may be noted that the impedance spectroscopy assumes piece-wise linearity of the solar cell characteristics, lending itself for easy measurement and modeling. This assumption is valid as the signal amplitude is less than thermal voltage (VT). Since, the parameters are measured under steady state, the values are more stable and accurate.
An attempt has also been made to correlate the measured AC parameters with the requirements of switching charge controllers. These correlations can be used to design the switching controllers for device rating, circuit stability and other aspects.
16
Anil, Kumar R. "Measurement Of Solar Cell AC Parameters Using Impedance Spectroscopy." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/203.
Full textAbstract:
Photovoltaic (PV) conversion of solar energy appears to be one of the most promising ways of meeting the increasing future energy demand. In space, photovoltaic power source is the only alternative. The demand for higher power has necessitated the use of high speed switching charge controller and power conditioner. To design an efficient and reliable switching charge controller, the static (I-V) and dynamic (AC) characteristics of a solar cell need to be understood.
The AC parameters of a solar cell can be measured either by Frequency Domain technique or by Time Domain technique. In frequency domain technique, a small signal is applied about the operating point and the AC parameters are measured. Hence, in the frequency domain technique the steady state values of AC parameters at a particular operating condition are measured. In time domain technique, a transient measurement is made where the cell voltage varies from short-circuit to open circuit or vice versa. Hence, this technique gives only the time constant of a solar cell.
The impedance spectroscopy is a frequency domain technique widely used in electro chemistry to study battery characteristics. In the present investigation, the impedance spectroscopy is proposed for measuring the AC parameters of solar cells. An experimental set-up has been developed to measure the solar cell AC parameters.
The AC parameters of Silicon (BSR and BSFR) solar cells and GaAs/Ge solar cells are measured using impedance spectroscopy (IS). The cell capacitance, the parallel resistance and the series resistance are measured and compared. GaAs/Ge solar cell has shown only transition Capacitance throughout its operating range while silicon (BSR and BSFR) solar cells exhibited both transition and diffusion capacitances. Theoretical and experimental values of the cell parallel resistance are compared and are in good agreement. While the diode factor in silicon solar cell varies from 2 to 1, where as in GaAs/Ge solar cell it varies from 4 to 2 to 1. Measurements conducted using open circuit voltage buildup (time domain technique) on silicon BSR solar cell shows that the collected data can be used for the restricted purpose of measuring cell transient response. The dime domain technique could not estimate the solar cell.
It may be noted that the impedance spectroscopy assumes piece-wise linearity of the solar cell characteristics, lending itself for easy measurement and modeling. This assumption is valid as the signal amplitude is less than thermal voltage (VT). Since, the parameters are measured under steady state, the values are more stable and accurate.
An attempt has also been made to correlate the measured AC parameters with the requirements of switching charge controllers. These correlations can be used to design the switching controllers for device rating, circuit stability and other aspects.
17
Jayaraman, Arjun. "Electrical impedance characterization of microporous films at elevated temperatures with interdigitated design." Diss., Connect to online resource - MSU authorized users, 2008.
Find full textAbstract:
Thesis (M.S.)--Michigan State University. Dept. of Electrical and Computer Engineering, 2008.Title from PDF t.p. (viewed on Aug. 7, 2009) Includes bibliographical references (p. 58-59). Also issued in print.
18
Mokhberi, Shiva. "ELECTRICAL BIOIMPEDANCE CEREBRAL MONITORING : A Study of Cerebral Impedance Variation." Thesis, KTH, Skolan för teknik och hälsa (STH), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-190876.
Full textAbstract:
Stroke is amongst the leading causes of death and disability worldwide. Today diagnosis of Stroke is restricted to fixed imaging facilities which do not provide a rapid diagnostic. A portable device which could provide a non invasive assessment of stroke would therefore decrease the time of diagnosis and increase the chance of survival. Recent studies have confirmed that Implementing Electrical Bioimpedance in a portable device could provide a reliable means for Stroke diagnostic. However in order to be able to use the brain impedance as an indicator of Stroke, the invariance of brain impedance with time in healthy individuals should be studied first. Experimental Bioimpedance Spectroscopy (BIS) measurements from a healthy control group of 10 subjects have been used in this study to inspect the variation of brain impedance in the span of two weeks. The results of this study suggest that the cap which was used for brain impedance measurements together with the available device have not been an optimal way of measuring the brain impedance and therefore have affected the data by causing artifacts for the results. With the artifacts available in the data acquired in this study it is not possible to make any statements about the variation of brain impedance and therefore a deeper analysis of collected data using descriptive analysis is required in order to be able to judge on the significance of the obtained errors. In the future a larger study group should be considered in order to increase the predictive power of the observations.Stroke är bland de ledande orsakerna till död och funktionshinder i hela världen.I dagsläget är diagnos av stroke begränsad till fasta bildenheter som inte möjliggör en snabb diagnos. En bärbar enhet som möjliggör en icke invasiv bedömning av sjukdomen skulle minska diagnos tiden och följaktligen öka chansen att överleva sjukdomen. Genomförda studier i ämnet har bekräftat att implementering av Electrical Bioimpedance i en bärbar enhet kan räknas som ett effektivt sätt för Stroke diagnostik. För att kunna använda hjärnans impedans för Stroke diagnostik, bör först en studie av hjärnans impedans på friska individer utföras för att kunna visa att impedansen är oförändrad med tiden. Experimentell Bioimpedans Spektroskopi (BIS) mätningar från en frisk kontrollgrupp av 10 försökspersoner har utförts i denna studie för att inspektera variationen av hjärnans impedans under två veckor. Resultaten från denna studie tyder på att sättet av impedans mätningen i dagsläget är inte optimalt. Artefakter presenterad i resultatet gör det omöjligt för att kunna komma till ett beslut om hjärnans impedans variation . För fortsätta studier bör man överväga en större kontrollgrupp och även en analysering av data med hjälp av t-statistik som var inte inom ramen av denna studie.
19
Waligo, Alfred. "Condition monitoring of lithium-ion batteries using broadband multisine excitation and electrochemical impedance spectroscopy." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/28109.
Full textAbstract:
Electrochemical Impedance Spectroscopy (EIS) is a well-known technique that has been employed on various electrochemical cells to obtain their impedance spectra. Lithium-ion(Li-ion) cells are some of the cells to which it has been applied. The impedance spectra obtained from EIS can be used to estimate various batteries State of Health (SOH) and State of Charge (SOC) characteristics. The lengthy acquisition time associated with standard EIS makes it unsuitable for rapid on-line impedance measurements. Alternative methods that take a shorter time have therefore been proposed. This study compares the spectra obtained by the Harmonic Compensated Synchronous Detection (HCSD) broadband signal technique with the EIS and a custom Broadband Impedance Spectroscopy (BIS) technique, at different states of charge, which mimic a real-time load. The test cells are industry standard Nickel-Cobalt and Manganese Oxide (NCM) Li-ion cells. The BIS technique is like HCSD in the selection of frequencies; however, the amplitude of the excitation broadband signal is varied to match the impedance magnitude response of the cell. Also, parameter extraction is performed on both EIS and BIS techniques for fault detection purposes.
20
Zhao, Yanlin. "Methods for electrical impedance spectroscopy and tomography characterising particles in suspensions and crystallisation processes." Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/3409/.
Full textAbstract:
Electrical impedance spectroscopy (EIS) is a method used to study the frequency dependence of the dielectric properties of colloidal suspensions by applying an alternating electric field. When an alternating electric field is applied, a dipole moment can be induced on a charged-particle due to the relative motion between the particles and their electric double layer. The macroscopic display of induced dipole moment is usually represented by the impedance parameters, including the impedance real part, imaginary part, phase angle and the relaxation frequency. These quantities are related to the size, shape and surface of the dispersed particles, the nature of the dispersed medium, and also the concentration of the particles. This thesis describes a fundamental study of the EIS method applied to colloidal particles. The relationship between the impedance parameters and the properties of particle suspensions is investigated. The study reveals the effects of particle size, particle concentration and ionic concentration dependence on the detected impedance parameters. Based on the study, new methods, including modelling, signal process, test set-up and data analysis, for characterisation of particles in suspensions are developed through the experimental approach and theoretical analysis. The methods are verified with silica suspensions and applied to crystallisation processes. The online measured electrical impedance spectra associated with L-glutamic acid nucleationgrowth processes and a polymorphic transformation are analysed. It is demonstrated that the methods can be applied for on-line monitoring of the particle size and polymorphs in crystallisation processes. Electrical impedance tomography based on EIS measurement conducted with different materials, including non-conductive plastic bar, banana, and silica suspensions are studied. The responses of electric polarisation of colloidal particles on tomographic images can be observed. However, the difference in particle size cannot be observed in the tomographic images possibly due to the limits of the imaging resolution from an 8-electrode sensor and the signal quality affected by the limits of the common mode voltage rejection ratio of the instrument.
21
Beltrán, Pitarch Braulio. "Advanced characterization of thermoelectric materials and devices by impedance spectroscopy." Doctoral thesis, Universitat Jaume I, 2020. http://hdl.handle.net/10803/670007.
Full textAbstract:
Els dispositius termoelèctrics (TEs) poden convertir directament calor en electricitat o usar electricitat per crear una diferència de temperatura, no obstant això, actualment no estan molt estesos a causa de la seua baixa eficiència. El desenvolupament de nous materials més eficients es basa típicament en l'optimització de la figura de mèrit adimensional, que està determinada per tres propietats del material: el coeficient Seebeck (S), la conductivitat elèctrica (σ) i la conductivitat tèrmica (λ), i també la temperatura (T). Per tant, la determinació d'aquestes propietats en funció de la temperatura és un pas necessari en el desenvolupament de qualsevol material nou. Lamentablement, la caracterització de tots aquests paràmetres requereix temps i és tediosa. Per aquesta raó, l'objectiu principal d'aquest treball és avançar en l'aplicació de l’espectroscòpia d’impedància (IS) en el camp de la termoelectricitat per a establir-la potencialment com un mètode estàndard en aquest camp.Thermoelectric (TE) devices can directly convert heat into electricity or use electricity to create a temperature difference, however, they are not widely spread currently due to their low efficiency. The development of new, more efficient materials is typically based on the optimization of the dimensionless figure of merit, which is determined by three material properties: the Seebeck coefficient (S), the electrical conductivity (σ) and the thermal conductivity (λ), and also the temperature (T). Hence, the determination of these properties as a function of temperature is a necessary step in the development of any new material. Regrettably, the characterization of all these parameters is quite lengthy and tedious. For this reason, the main objective of this work is to advance the application of impedance spectroscopy (IS) in the TE field to potentially establish it as a standard method in thermoelectricity.
22
Degache, Amelie. "Electrical impedance spectroscopy applied to the chronic monitoring of the fibrosis induced by cardiac active implants." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0432.
Full textAbstract:
Les arythmies cardiaques représentent environ 50% des maladies cardiovasculaires qui sont la première cause de mortalité dans le monde. Les implants médicaux jouent un rôle majeur dans le traitement de ces arythmies. En France c’est environ 250 000 patients qui sont équipés d’un implant cardiaque et qui nécessitent un suivi régulier. Ces implants utilisent les dernières technologies de micro-nano électronique et possèdent un boitier de stimulation qui est placé en sous-cutané, connecté aux électrodes via une sonde intraveineuse. Un des principaux points faibles de tout implant réside dans l’interface électrode-tissu, en raison d’une réaction inflammatoire soutenue appelée la fibrose. Ce phénomène compromet la biocompatibilité de l’implant, encapsulant la sonde avec un tissu « isolant ». Cela crée des adhérences le long de la sonde et au niveau de l’électrode, ce qui entraine souvent une hausse des seuils de stimulation au cours du temps et une diminution des durées de vie des batteries. Cette réponse est connue et peut être minimisée lors de l’implantation grâce à des sondes à élution de stéroïdes mais la fibrose reste tout de même un obstacle pour les implants, justifiant notre intérêt d’étude sur le long terme de la biocompatibilité des implants cardiaques.La compréhension des mécanismes de la fibrose est primordiale pour ce travail. La fibrose est due à une activation et différentiation de certaines cellules cardiaques sous une contrainte mécanique, et le tissu cardiaque se retrouve modifié localement. Pour caractériser cette modification, on utilise la mesure d’impédance qui consiste à envoyer un courant électrique sinusoïdal I et recueillir la tension résultante U dans le tissu, l’impédance Z est le ratio U/I. en fonction de la fréquence de mesure, on peut explorer le tissu à une échelle microscopique ou macroscopique. Comme les patients sont déjà équipés de sondes cardiaques reliées à un circuit de stimulation qui peut aussi enregistrer l’activité cardiaque, l’idée principale de ce travail est d’examiner l’utilisation d’une mesure électrique qui pourrait caractériser l’encapsulation fibrotique de la sonde, avec pour objectif final d’embarquer cette méthode de caractérisation dans le circuit implanté. Cela nous amène à la problématique de ce projet : est-ce que la fibrose qui se développe autour des sondes cardiaques a une signature électrique ?Mon travail de thèse s’organise en trois axes. Deux axes expérimentaux sont conduits aux niveaux cellulaire et tissulaire. On envisage en plus un axe discutant la faisabilité de mesures d’impédance embarquées pour des conditions proches de l’in vivo. La partie tissulaire ou ex vivo présente la caractérisation de différentes natures de tissu, sain ou collagéneux, et a été développée à l’IHU LIRYC, sur des ventricules de cochons ou de brebis avec des sondes cardiaques implantées chez l’homme. Les spectres d’impédance obtenus sont analysés avec des modèles électriques connus et dont les paramètres sont extraits pour chaque type de tissus. Une analyse statistique montre que les deux natures de tissu sont caractérisées par des paramètres significativement différents. La partie cellulaire ou in vitro présente la caractérisation électrique, par mesure d’impédance, et biologique, par marquages immunocytochimiques, d’un modèle cellulaire de fibrose. Ce modèle est développé en cultivant des cellules cardiaques humaines, activées ou non par un facteur de croissance. Après une analyse statistique, les valeurs d’impédance des cultures activées montrent une différence significative par rapport aux cultures non activées, tandis que la caractérisation biologique montre une augmentation du nombre des cellules activées au cours du temps. Le dernier axe présente des résultats préliminaires sur de mesure d’impédance embarquée en vue d’une utilisation ultérieure in vivoCardiac arrhythmias represent about 50% of the cardiovascular diseases which are the first cause of mortality in the world. Implantable medical devices play a major role for treating these cardiac arrhythmias. In France, about 250.000 patients are equipped with an implanted device for arrhythmia treatment and need a regular monitoring. These devices use the latest technology of micro-nano-electronics and integrate a subcutaneous pulse generator connected to electrodes placed into the heart via intravenous leads. One of the main weaknesses of every implantable device lies in the electrode-tissue interface due to a sustained inflammatory response called fibrosis. This phenomenon jeopardizes the device biocompatibility, because it encapsulates the stimulation lead with an “insulating” tissue, creating adherences along the lead and often leading to an increase of the stimulation threshold over time and a larger electrical consumption. This response is well-known and minimized during the implantation surgery thanks the use of steroid-elution electrodes, however fibrosis still remains an impediment even for the most recent devices, enhancing the interest of studying long-term biocompatibility of cardiac implanted devices.The understanding of fibrosis mechanisms is essential for this work. It consists in some cardiac cells activation and differentiation under a mechanical stress, inducing fibrosis initiation and modifying locally the active cardiac tissue. To characterize this modification, we use electrical impedance measurements, consisting in sending a sinusoidal electrical current I and then measuring the resulting voltage U in the tissue; the impedance Z is the U/I ratio. Depending on the frequency of the measurement signal, we can explore the tissue from the microscopic to the macroscopic scales. As a patient is already equipped with cardiac leads connected to a stimulation device which can also record the cardiac electrical activity, the main idea of this work is to investigate the use of an electrical measurement that could characterize the fibrotic lead encapsulation, with the final objective to embed this characterization method in the implanted circuit. This brings us to the main question of our project: does the fibrosis developing around the cardiac leads have an electrical signature?My thesis work is organized along three axes. Two experimental axes are conducted at cellular and tissue levels, on in vitro or ex vivo models. In addition, an axis studying the feasibility of embedded impedance measurement for in vivo mimicking conditions is also discussed. The ex vivo part presents the characterization of tissue of different natures, healthy or collagenous, it was developed with the IHU LIRYC laboratory, on porcine or ovine cardiac tissue (ventricles mainly), with stimulation electrodes used on patients The impedance spectra are analyzed using a known electrical model from which characteristic parameters of the two tissue types are extracted. After statistical analysis, these parameters are found to be significantly different allowing us to distinguish both tissue types. The in vitro part presents the electrical characterization, using impedance measurements, in parallel to the biological characterization, using immunocytochemistry, of a cellular fibrosis model. It consists in culturing human cardiac cells, activated or not by a growth factor. After a statistical analysis, the impedance values show a significantly different signature for cultures with growth factor, with respect to sham cultures, while the biological characterization confirmed the presence of more activated and differentiated cells over time. The last axis gives preliminary results of embedded impedance measurements in custom circuits
23
Blanco, Hernández David. "Development of a software tool for electrical bioimpedance spectroscopy analysis." Thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-18827.
Full textAbstract:
Electrical Bioimpedance measurement has been used in clinical practice for several years for non-invasive monitoring. In recent years new applications of electrical bioimpedance measurements based in the spectral analysis has been validated.This fact have encouraged the use of spectral analysis on Electrical Bioimpedance measurements and it is a wide spread idea that spectral analysis of electrical bioimpedance data is going to open the door for new indicators for health assessment.The intended goal of this project is to develop a software tool, based in Matlab, that allows researchers to perform, both spectral and time signal analysis on the measurements performed Electrical Bioimpedance Spectrometers. This tool must incorporate the necessary display capabilities to allow quick visual inspection and visualization of the analysis results.Once this tool has been implemented, spectral analysis and validation of classification features will be possible in an easy way accelerating the process of test and analysis of experimental data analysis. This task is always critical in any research or clinical study.To facilitate the spectral analysis of electrical bioimpedance data will contribute to the developing of novel methods of non-invasive diagnosis and monitoring.Uppsatsnivå: D
24
García, Sánchez Tomás. "Development of devices and techniques for electroporation and electrical impedance spectroscopy analysis of adherent cells." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/401439.
Full textAbstract:
The present PhD dissertation is focused on the design and implementation of a microelectrode system capable of performing electroporation and electrical impedance measurements to adherent cell monolayers cultured in standard multiwell plates. Along the document, the ability of the proposed device to provoke cell electropermeabilization is first demonstrated. Subsequently, the system is applied in monitoring of the electroporation process by means of fast electrical impedance spectroscopy measurements. The original concept of the proposed system resides on the momentary placement of the microelectrodes above the cell monolayer avoiding physical contact with the cells by means of microseparators. A modification of the standard printed circuit board (PCB) fabrication technology that helps to improve the current density distribution is developed to manufacture the final microelectrode prototypes.This technology allows producing disposable devices at very low cost. The performance of the device is tested with different cell lines and using different molecules such as DNA and siRNA. The results confirm its usefulness but show considerable differences between permeabilization and transfection results. Subsequently, the specific characteristics of the device to perform electrical impedance measurements with a four-electrode method during the electroporation treatment are fully exploited. In this thesis a multisine-based measuring system capable of acquiring impedance spectra continuously with a time resolution of 1 spectrum/ms is used. In contrast to previous studies, the speed of the measuring system allows to perform full impedance spectroscopy measurements in the time gap between consecutive electroporation pulses and not only before and after the complete electric field application. The impedance results at low frequency show the ability of the system to detect the fast cell membrane resealing dynamics immediately after each pulse. These fast dynamics are related to the so called short-lived pores and follow a double exponential behavior. Also, an accumulated slow impedance decrease along the complete process is observed related to the long-lived pores. Complementary, the high frequency impedance response shows how the effect of the conductivity variation caused by the diffusion of ions between the intracellular and extracelluar media has also an impact on the impedance measurements. Different approaches are proposed in the analysis of the measurements of four different cell lines: the direct observation of impedance magnitude and phase, the study of Cole model parameters and the use of an equivalent electrical circuit. The comparative analysis suggest that for the detection of fast cell membrane dynamics, phase of impedance is preferable to its magnitude because it is less disturbed by the collateral conductivity variations. After deep analysis of Cole parameters, an equivalent time constant combining the information of the Cole parameters tau and alpha is proposed as a general analysis parameter for the fast membrane changes. Lastly, the equivalent circuit is useful in order to give or to confirm a physical interpretation to the observed results. Finally, regarding the slow impedance decrease, it shows a non linear permeabilization rate with pulse number for high electric field intensities, suggesting the existence of a limit for new pore creation with increasing pulse number. It is also demonstrated how the total impedance variation at the end of the treatment can be used as a reliable marker of the success of cell eletropermeabilization with some advantages with respect to traditional chemical methods. The results shown in this thesis demonstrate how fast electrical impedance spectroscopy measurements during an electroporation procedure represent a reliable and alternative method for online monitoring the fast changes produced in the membranes of the sample under treatment.La presente tesis doctoral se centra en el diseño y la implementación de un sistema de microelectrodos específicamente concebidos para su aplicación en electroporación y medidas de espectroscopia de impedancia eléctrica (EIS) de células adherentes creciendo en placas multipocillo estándar. En primer lugar se demuestra la habilidad de sistema propuesto para provocar la electropermeabilización celular. A continuación, el sistema se aplica en la monitorización del proceso de electroporación mediante medidas rápidas de EIS. La novedad en el concepto del sistema propuesto reside en el posicionamiento momentáneo del sistema de microelectrodos sobre la monocapa celular evitando el contacto físico por medio de microseparadores. Para la fabricación del prototipo final se desarrolló una modificación en la tecnología de fabricación de circuito impreso estándar que ayuda a mejorar la distribución de la densidad de corriente. Esta tecnología permite la producción de dispositivos desechables a precio bajo. El funcionamiento del sistema se testa con diferentes líneas celulares y diferentes moléculas como ADN y siARN. Los resultados confirman su utilidad, pero muestran diferencias considerables entre las tasas de permeabilización y de transfección obtenidas. Posteriormente, se explotan completamente las características específicas del dispositivo para la obtención de medidas de impedancia eléctrica durante la electroporación utilizando una estrategia a 4 hilos. En esta tesis se utiliza un sistema de medida basado en multisenos capaz de adquirir espectros de impedancia con una resolución temporal de 1 espectro/ms. En contraposición a estudios previos, la velocidad del sistema de medida permite realizar múltiples medidas completas de espectroscopia en el tiempo entre pulsos de electroporación consecutivos y no sólo antes y después del tratamiento. Los resultados a baja frecuencia muestran la habilidad del sistema para detectar la dinámica rápida de recuperación de la membrana después de cada pulso. Esta dinámica es debida a los conocidos como poros de vida corta y sigue un comportamiento exponencial doble. Además, se observa un descenso lento y acumulado a lo largo del proceso completo debido a los poros de vida larga. Por otro lado, la respuesta de impedancia a alta frecuencia muestra cómo el efecto de la variación de conductividad causada por la difusión de iones entre los medios intra y extracelular tiene impacto en las medidas de impedancia. Se proponen varias aproximaciones para el análisis de las medidas realizadas en cuatro líneas celulares diferentes: la observación directa de la magnitud y fase de la impedancia, el estudio de los parámetros del modelo de Cole y el uso de un circuito eléctrico equivalente. El análisis comparativo sugiere que para la detección de los cambios rápidos en la membrana, la fase de la impedancia es preferible a su magnitud debido a que el cambio colateral de conductividad afecta menos a la fase. Tras el análisis profundo de los parámetros de Cole, se propone la utilización de una constante de tiempo equivalente combinando la información de tau y alfa del modelo de Cole como un parámetro de análisis general. Finalmente, el circuito equivalente es útil para confirmar y ayudar a dar una interpretación física de los resultados observados. En cuanto al descenso lento de impedancia, se observa una tasa de permeabilización no lineal para las intensidades de campo eléctrico más altas, sugiriendo la existencia de un límite para la creación de nuevos poros con el número de pulso. También se demuestra cómo la variación total de impedancia al final del tratamiento puede ser utilizada como un marcador del éxito de la permeabilización celular con ventajas respecto de los métodos químicos tradicionales. Los resultados presentados en esta tesis muestran como las medidas rápidas de EIS durante un procedimiento de electroporación son un método alterativo fiable para la monitorización en tiempo real de los cambios producidos.
25
Li, Yingjia. "Low-Voltage Electrowetting on Dielectrics Integrated and Investigated with Electrical Impedance Spectroscopy (LV-EWOD-EIS)." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://hdl.handle.net/11858/00-1735-0000-002E-E4D3-9.
Full text
26
Moore, Sean. "Online condition monitoring of lithium ion batteries by performing impedance spectroscopy using a DC-DC converter." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29186.
Full textAbstract:
Li-Ion batteries are currently being used extensively in a variety of applications such as portable electronics, electric vehicles and grid storage applications, due to the high demand for high power and high energy density storage batteries. However, the usage of Li-Ion batteries requires extensive condition monitoring to increase overall performance and life expectancy. This research is focused on implementing rapid online condition monitoring techniques, using signal injection via the associated power converter in the battery management system. The technique implemented in this work is known as Electrochemical Impedance Spectroscopy (EIS). EIS is a well-known technique, that has been used to characterize an electrochemical cell’s behaviour and state by monitoring changes in the cell's impedance. This is accomplished by injecting currents at different frequencies into the battery and measuring the voltage response. This technique is conventionally implemented, using standard Frequency Response Analysers (FRA), while the battery is disconnected from the load (offline) due to the long procedural times involved. This has limited the use of EIS to laboratory testing. In recent years, there has been literature regarding incorporating EIS testing into the battery system, which is done in mainly 2 ways, by including a linear amplifier into the system to inject the current perturbations directly, or by using the existing circuitry in the BMS (typically the DC-DC converter) to inject the current perturbations using various control techniques. Although, these strategies have been applied in literature for online systems, they are still riddled with a lengthy EIS measurement time issue. This work seeks to significantly reduce the associated testing time with the use broadband signals to implement Impedance Spectroscopy for online systems via the associated BMS converter. Broandband Impedance Spectroscopy (BIS) is implemented by injecting a signal with multiple frequencies concurrently as this allows for quicker measurement. The main contribution of this work is the real-time implementation of a multi-sine broadband excitation via a bi-directional converter that can be used in a varying system. The results obtained were compared to results from an industry standard FRA and showed to produce Nyquist plots with a reasonable error.
27
Mohammad, Naim Nur Nafisah. "Modelling the ageing behaviour of supercapacitors using electrochemical impedance spectroscopy for dynamic applications." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/29169/.
Full textAbstract:
Diagnosis of ageing mechanisms in supercapacitors is made difficult by the enforcement of various ageing factors in the current ageing tests. The thesis presents the exact determination of the ageing mechanism by separating the impacts of high temperature, current cycling and constant voltage applications in accelerated ageing tests. The state of health (SOH) of the supercapacitors are monitored periodically with electrochemical impedance spectroscopy, cyclic voltammetry and constant current test to observe the evolution of ageing. The thesis identifies patterns of ageing from the changes at supercapacitor impedance. The thesis also presents the cause of the increase in ESR and the loss of capacitance in supercapacitors. High temperature application causes the appearance of high frequency semicircle which reflects the damage at the electrode-current collector interface. A tilt of the impedance line at low frequencies reflects modifications of electrodes and it is most sensitive to current cycling and constant voltage applications. The increase in ESR is observed to be caused by a single ageing mechanism while the capacitance loss is caused by multiple interactions of these ageing mechanisms at the same time. The thesis develops a supercapacitor model by means of electrical equivalent circuit. The model is divided into two parts based on the changes in its SOH: the baseline model represents the early stage of the supercapacitor life and the ageing model represents the phase of ageing. The models show dynamic interactions between ageing process and supercapacitor electrical performance. The supercapacitor model, in the form of fractional-order model, reduces the number of circuit components and shows excellent electrical behaviour particularly at the open circuit voltage decay and voltage recovery period. The parameterisation of model parameters shows that aged supercapacitors experience an increase of distributed resistance in the electrode pores and an increase of diffusion impedance at high temperature.
28
Jacobs, John David. "Online Impedance Spectroscopy of Thermoset Nanocomposites for Materials In Situ Process Control." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1242764995.
Full text
29
Karnes, Michael. "Electrochemical Characterization of ex vivo Human Hepatic Tissues Containing Colorectal Metastases and Quantification of Spatial Error in Electrical Impedance Mapping of Soft Tissues." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1450118548.
Full text
30
Bhatnagar, Purva. "A microcontroller-based Electrochemical Impedance Spectroscopy Platform for Health Monitoring Systems." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439307617.
Full text
31
Berner, Tim, and Klaus-Dieter Becker. "Electrical conductivity relaxation experiments on single crystalline cobalt silicate Co 2 SiO 4 by using impedance spectroscopy." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186788.
Full text
32
Berner, Tim, and Klaus-Dieter Becker. "Electrical conductivity relaxation experiments on single crystalline cobalt silicate Co 2 SiO 4 by using impedance spectroscopy." Diffusion fundamentals 12 (2010) 45, 2010. https://ul.qucosa.de/id/qucosa%3A13885.
Full text
33
Macias, Macias Raul. "Towards Wearable Spectroscopy Bioimpedance Applications Power Management for a Battery Driven Impedance Meter." Thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-19428.
Full textAbstract:
In recent years, due to the combination of technological advances in the fields ofmeasurement instrumentation, communications, home-health care and textile-technology thedevelopment of medical devices has shifted towards applications of personal healthcare.There are well known the available solutions for heart rate monitoring successfully providedby Polar and Numetrex. Furthermore new monitoring applications are also investigated. Amongthese non-invasive monitoring applications, it is possible to find several ones enable bymeasurements of Electrical Bioimpedance.Analog Devices has developed the AD5933 Impedance Network Analyzer which facilitatesto a large extent the design and implementation of Electrical Bioimpedance Spectrometers in amuch reduced space. Such small size allows the development of a fully wearable bioimpedancemeasurement.With the development of a Electrical Bioimpedance-enable wearable medical device in focusfor personal healthcare monitoring, in this project, the issue of power management has beentargeted and a battery-driven Electrical Bioimpedance Spectrometer based in the AD5933 hasbeen implemented. The resulting system has the possibility to operate with a Li-Po battery with apower autonomy over 17 hours.
34
Burtone, Lorenzo [Verfasser], Frank Akademischer Betreuer] Ellinger, and Karl [Akademischer Betreuer] [Leo. "Electrical Characterization of Organic Devices and Solar Cells by Impedance Spectroscopy / Lorenzo Burtone. Gutachter: Frank Ellinger ; Karl Leo." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://d-nb.info/1068447303/34.
Full text
35
Ghasemi, Samira. "Emulsion polymerisation in the presence of hydrophilic comonomers." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/13274.
Full textAbstract:
Emulsion polymerisations are preferably stabilised electrosterically through the addition of hydrophilic comonomers having carboxyl functional groups. Furthermore, the incorporation of these comonomers can enhance the properties of the final polymer product. Despite their industrial importance, there is a lack of kinetic studies on these systems. The hydrophilic comonomer preferentially polymerises in the aqueous phase, leading to grafted or embedded hydrophilic chains anchored on the particle surface forming a hairy layer. Developing a mathematical model, it was found that the inhibition effects of the hairy layer of poly-AA chains were more profound compared to poly-MAA chains. The copolymerisation of styrene with MAA was monitored using reaction calorimetry technique for the first time. Using this technique, the enthalpy of copolymerisation of styrene with MAA was estimated and it was found that though the enthalpy of copolymerisation of styrene and MAA is lower than that of styrene alone, the heat of reaction was much higher. This was attributed to a higher polymerisation rate in the presence of MAA comonomer. Since various rapid events occur during emulsion polymerisation that may not be detected using temperature monitoring a novel on-line monitoring technique via high resolution electrical impedance spectroscopy (EIS) was developed for this purpose. It was shown that conductance changes with time at 1 kHz could provide information about properties of various stages of emulsion polymerisation systems. At lower frequencies (i.e., 1 Hz), however, EIS data could successfully detect the particle size evolution. Also, the addition of MAA to the reactor facilitated particle formation, and was reflected by a shorter pre-nucleation period compared with similar experiments without MAA. Furthermore, it was observed that polymerisation of MAA preceded that of styrene.
36
Bonakdar, Mohammad. "Microdevices for Investigating Pulsed Electric Fields-Mediated Therapies at Cellular and Tissue Level." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/81384.
Full textAbstract:
Recent attempts to investigate living systems from a biophysical point of view has opened new windows for development of new diagnostic methods and therapies. Pulsed electric fields (PEFs) are a new class of therapies that take advantage of biophysical properties and have proven to be effective in drug delivery and treating several disorders including tumors. While animal models are commonly being used for development of new therapies, the high cost and complexity of these models along with the difficulties to control the electric field in the animal tissue are some of the obstacles toward the development of PEFs-based therapies. Microengineered models of organs or Organs-on-Chip have been recently introduced to overcome the hurdles of animal models and provide a flexible and cost-effective platform for early investigation of a variety of new therapies. In this study microfluidic platforms with integrated micro-sensors were designed, fabricated and employed to study the consequences of PEFs at the cellular level. These platforms were specifically used to study the effects of PEFs on the permeabilization of the blood-brain barrier for enhanced drug delivery to the brain. Different techniques such as fluorescent microscopy and electrical impedance spectroscopy were used to monitor the response of the cell monolayers under investigation. Irreversible electroporation is a new focal ablation therapy based on PEFs that has enabled ablation of tumors in a non-thermal, minimally invasive procedure. Despite promising achievements and treatment of more than 5500 human patients by this technique, real-time monitoring of the treatment progress in terms of the size of the ablated region is still needed. To address that necessity we have developed micro-sensor arrays that can be implemented on the ablation probe and give real-time feedback about the size of the ablated region by measuring the electrical impedance spectrum of the tissue.Ph. D.
37
Li, Qin. "The study of DNA dynamics at carbon electrode surface toward DNA sensors by fluorescence and electrochemical impedance spectroscopy." Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/9159.
Full textAbstract:
Master of ScienceDepartment of Chemistry
Jun Li
This study is focused on exploring the mechanisms of DNA dynamics at carbon electrode surfaces under a strong electric field for the development of novel DNA hybridization sensors. Oligonucleotides with FAM6 attached at the distal end are covalently tethered on the carbon electrode surface. The fluorescence emission from the FAM6 is strongly quenched in close proximity to the electrode surface. The modulation to the fluorescence intensity is correlated with the reversible reorientation of the negatively charged DNA molecules under the electric field within the electric double layer. The orientation dynamics are apparently determined by the interplay of the electropotential, salt concentration, and stiffness of the DNA molecules. We have observed that dsDNAs switch with fast dynamics (in < 0.05 second) followed by relaxation at a slower rate (in > 0.1 second) when the electric field is altered by stepping the electropotential to a more positive or negative value. The DNA reorientation exhibits strong dependence on the PBS buffer concentration and electric double layer thickness. A preliminary calculation based on dipole-surface energy transfer theory indicates that the critical distance between FAM6 and glassy carbon surface is 10.95 nm. In connection with the fluorescence study, the effect of DNA hybridization on electrochemical impedance spectroscopy (EIS) has also been investigated by two methods in an attempt to develop a fast electronic detection method. First, EIS at high AC amplitude (141 mV rms) with DNA-modified glassy carbon electrodes before and after target DNA hybridization have shown notable change at high frequencies, likely related to the DNA reorientation processes. Second, reversible EIS detection of DNA hybridization has been demonstrated with patterned regular carbon nanofiber arrays at normal AC amplitude (10 mV rms). The combination of these two methods will be explored in future studies. The effects of the electric field on surface-tethered molecular beacons (MBs) have also been studied with fluorescence spectroscopy. An increase in fluorescence at negative bias is observed accompanying the opening of the MB stem, which leads to larger separation between fluorophore and quencher. At positive bias, the rehybridization of the MB stem leads to a decrease in fluorescence intensity.
38
BANDI, DILIP KUMAR. "Small Signal Impedance and Optical Modulation Bandwidth Characterization and Modeling of Organic Light Emitting Devices." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1204912125.
Full text
39
Yuan, Qifan. "Physical, electrical and electrochemical characterizations of transition metal compounds for electrochemical energy storage." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/71869.
Full textAbstract:
Electrochemical energy storage has been widely used in various areas, including new energy sources, auto industry, and information technology. However, the performance of current electrochemical energy storage devices does not meet the requirements of these areas that include both high energy and power density, fast recharge time, and long lifetime. One solution to meet consumer demands is to discover new materials that can substantially enhance the performance of electrochemical energy storage devices. In this dissertation we report four transition metal materials systems with potential applications in electrochemical energy storage.
Nanoscale and nanostructured materials are expected to play important roles in energy storage devices because of their enhanced and sometimes unique physical and chemical properties. Studied here is the comparative electrochemical cation insertion into a nanostructured vanadium oxide, a promising electrode material candidate, for the alkali metal ions Li+, Na+ and K+ and the organic ammonium ion, in aqueous electrolyte solutions. Observed are the distinctive insertion processes of the different ions, which yield a correlation between physical degradation of the material and a reduction of the calculated specific charge. The results reveal the potential of this nanostructured vanadium oxide material for energy storage. Vanadium based electrochemical systems are of general interest, and as models for vanadium based solid-state electrochemical processes, the solution state and the solid-state electrochemical properties of two cryolite-type compounds, (NH4)3VxGa1-xF6, and Na3VF6, are studied. The electrochemical behavior of (NH4)3VxGa1-xF6 explored the possibility of using this material as an electrolyte for solid state energy storage systems.
Zeolite-like materials have large surface to volume ratios, with ions and neutral species located in the nanometer sized pores of the 3-dimensional framework, potentially yielding high energy density storage capabilities. Yet the insulating nature of known zeolite-like materials has limited their use for electrical energy storage. Studied here are two vanadium based zeolite-like structures, the oxo-vanadium arsenate [(As6V15O51)-9]∞, and the oxo-vanadium phosphate [(P6V15O51)-9]∞, where the former shows electronic conduction in the 3-dimensional framework. Mixed electronic and ionic conductivity, from the framework and from the cations located within the framework, respectively, is measured in the oxo-vanadium arsenate, and allows the use of this material in electrochemical double-layer capacitor configuration for energy storage. By contrast, the oxo-vanadium phosphate shows ionic conduction only. Lastly, a new strontium manganese vanadate with a layered structure exhibiting mixed protonic and electronic conductivity is studied. The various transition metal compounds and materials systems experimentally studied in this thesis showcase the importance of novel materials in future energy storage schemes.Ph. D.
40
Bhatnagar, Purva. "Multi-Frequency and Multi-Sensor Impedance Sensing Platform for Biosensing Applications." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1543999395772179.
Full text
41
Shi, Qinghai, Andreas Heinig, and Olfa Kanoun. "Design and evaluation of a portable device for the measurement of bio-impedance cardiography." Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-64632.
Full textAbstract:
Electrical impedance of biological matter is known as electrical bio-impedance or simply as bio-impedance. Bio-impedance devices are of great value for monitoring the pathological and physiological status of biological tissues in clinical and home environments. The technological progress in instrumentation has significantly contributed to the progress that has been observed during the last past decades in impedance spectroscopy and electrical impedance cardiograph. Although bio-impedance is not a physiological parameter, the method enables tissue characterization and functional monitoring and can contribute to the monitoring of the health status of a person. In this paper an inexpensive portable multi frequency impedance cardiograph device based on impedance spectroscopy technique has been developed. By means of this system the basic thoracic impedance range and the heart-action-caused changes of impedance can be measured and the hemodynamic parameters of the heart function can be determined. This system has small size and low current consumption. The impedance cardiograph signals of the electrodes configuration by Sramek, Penney and Qu in this work was measured; compared and summarized. The differences of the measuring method, the schematic circuit diagram, the measurement results and area of application between impedance cardiograph and impedance spectroscopy were discussed and compared. The performance of this sensor-system was evaluated.
42
Joshi, Salil Mohan. "Effect of heat and plasma treatments on the electrical and optical properties of colloidal indium tin oxide films." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52170.
Full textAbstract:
The research presented in this dissertation explores the possibility of using colloidal indium tin oxide (ITO) nanoparticle solutions to direct write transparent conducting coatings (TCCs), as an alternative route for TCC fabrication. ITO nanoparticles with narrow size distribution of 5-7 nm were synthesized using a non-aqueous synthesis technique, and fabricated into films using spin coating on substrates made from glass and fused quartz. The as-coated films were very transparent (>95% transmittance), but highly resistive, with sheet resistances around 10¹³ Ω/sq . Pre-annealing plasma treatments were investigated in order to improve the electrical properties while avoiding high temperature treatments. Composite RIE treatment recipes consisting of alternating RIE treatments in O₂ plasma and in Ar plasma were able to reduce the sheet resistance of as spin coated ITO films by 4-5 orders of magnitude, from about 10¹³ Ω/sq in as-coated films to about 3 x 10⁸ Ω/sq without any annealing. Plasma treatment, in combination with annealing treatments were able to decrease the sheet resistance by 8-9 orders of magnitude down to almost 10 kΩ/sq , equivalent to bulk resistivity of ~0.67 Ω.cm. Investigation into effectiveness of various RIE parameters in removing residual organics and in reducing the sheet resistance of colloidal ITO films suggested that while reactive ion annealing (RIE) pressure is an important parameter; parameters like plasma power, number of alternating O₂-Ar RIE cycles were also effective in reducing the residual organic content. Impedance spectroscopy analysis of the colloidal ITO films indicated the dominance of the various interfaces, such as grain boundaries, insulating secondary phases, charge traps, and others in determining the observed electrical properties.
43
Price, Dorielle T. "Optimization of Bio-Impedance Sensor for Enhanced Detection and Characterization of Adherent Cells." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4208.
Full textAbstract:
This research focuses on the detection and characterization of cells using
impedance-based techniques to understand the behavior and response of cells to internal/environmental changes. In combination with impedimetric sensing techniques, the biosensors in this work allow rapid, label-free, quantitative measurements and are very sensitive to changes in environment and cell morphology. The biosensor design and measurement setup is optimized to detect and differentiate cancer cells and healthy (normal) cells. The outcome of this work will provide a foundation for enhanced 3-dimensional tumor analysis and characterization; thus creating an avenue for earlier cancer detection and reduced healthcare costs.
The magnitude of cancer-related deaths is a result of late-diagnosis and the fact that cancer is challenging to treat, due to the non-uniform nature of the tumor. In order to characterize and treat individual cells based on their malignant potential, it is important to have a measurement technique with enhanced spatial resolution and increased sensitivity. This requires the study of individual or small groups of cells that make up the entire tissue mass.
The overall objective of this research is to optimize a microelectrode biosensor and obtain statistically relevant data from a cell culture using an independent multi-electrode design. This would provide a means to explore the feasibility of electrically characterizing cells with greater accuracy and enhanced sensitivity.
44
Moncoľ, Maroš. "Uhlíkové elektrody pro superkondenzátory." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218318.
Full textAbstract:
This master thesis deals with supercapacitors based on electrical double layer and proper carbon electrodes for this type of supercapacitors. In theoretical part of work is described theory of supercapacitors, energy storage principles and their properties. In the next part are described carbon materials, their properties and electrochemical methods of measurements that we used. In the experimental part is described preparation of electrodes, results and conclusion.
45
Li, Yingjia [Verfasser], Andreas [Akademischer Betreuer] Janshoff, Andreas [Gutachter] Janshoff, and Philipp [Gutachter] Vana. "Low-Voltage Electrowetting on Dielectrics Integrated and Investigated with Electrical Impedance Spectroscopy (LV-EWOD-EIS) / Yingjia Li ; Gutachter: Andreas Janshoff, Philipp Vana ; Betreuer: Andreas Janshoff." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://d-nb.info/1169396550/34.
Full text
46
LEITAO, FREDNER. "Obtencao de pos de zirconia estabilizada com itria com diferentes teores de silica." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10999.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:46:43Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:58:36Z (GMT). No. of bitstreams: 1 08288.pdf: 2858118 bytes, checksum: 5254a04c780740482622c95ca3afa37b (MD5)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
47
Detrich, Kahlil. "Electroding Methods for in situ Reverse Osmosis Sensors." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/31207.
Full textAbstract:
The purpose of this work is to develop and evaluate electroding methods for a reverse osmosis (RO) membrane that results in an in situ sensor able to detect RO membrane protein fouling. Four electroding techniques were explored: i) gold exchange-reduction, ii) encapsulated carbon grease, iii) â direct assembly processâ (DAP), and iv) platinized polymer graft. The novel platinized polymer graft method involves chemically modifying the RO membrane surface to facilitate platinization based on the hypothesis that deposition of foulant on the platinized surface will affect platinum/foulant/solution interfacial regions, thus sensor impedance. Platinized polymer graft sensors were shown to be sensitive to protein fouling.
Electrodes were characterized by their electrical properties, SEM and XPS. Assembled sensors were evaluated for sensitivity to electrolyte concentration and protein fouling. Micrographs showed coating layers and pre-soak solution influence gold exchange-reduction electrode formation. High surface resistance makes gold exchange-reduction an unsuitable method. Concentration sensitivity experiments showed carbon grease and DAP electroding methods produce unusable sensors. Carbon grease sensors have time-dependent impedance response due to electrolyte diffusion within the micro-porous polysulfone support. DAP electroded sensors proved quite fragile upon hydration; their impedance response is transient and lacks predictable trends with changes in concentration. A parametric study of the platinized polymer graft method shows amount of grafted monomer correlates to grafting time, and deposited platinum is a function of exchange-reduction repetitions and amount of grafted monomer. Platinized polymer graft sensors were fouled in both dead-end and cross-flow RO systems, and their impedance trends, while varying between sensors, indicate protein-fouling sensitivity.Master of Science
48
Srinivasaraghavan, Vaishnavi. "Bioimpedance spectroscopy of breast cancer cells: A microsystems approach." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/63921.
Full textAbstract:
Bioimpedance presents a versatile, label-free means of monitoring biological cells and their responses to physical, chemical and biological stimuli. Breast cancer is the second most common type of cancer among women in the United States. Although significant progress has been made in diagnosis and treatment of this disease, there is a need for robust, easy-to-use technologies that can be used for the identification and discrimination of critical subtypes of breast cancer in biopsies obtained from patients. This dissertation makes contributions in three major areas towards addressing the goal. First, we developed miniaturized bioimpedance sensors using MEMS and microfluidics technology that have the requisite traits for clinical use including reliability, ease-of-use, low-cost and disposability. Here, we designed and fabricated two types of bioimpedance sensors. One was based on electric cell-substrate impedance sensing (ECIS) to monitor cell adhesion based events and the other was a microfluidic device with integrated microelectrodes to examine the biophysical properties of single cells. Second, we examined a panel of triple negative breast cancer (TNBC) cell lines and a hormone therapy resistant model of breast cancer in order to improve our understanding of the bioimpedance spectra of breast cancer subtypes. Third, we explored strategies to improve the sensitivity of the microelectrodes to bioimpedance measurements from breast cancer cells. We investigated nano-scale coatings on the surface of the electrode and geometrical variations in a branched electrode design to accomplish this. This work demonstrates the promise of bioimpedance technologies in monitoring diseased cells and their responses to pharmaceutical agents, and motivates further research in customization of this technique for use in personalized medicine.Ph. D.
49
Chetham, Scott Matthew. "Measurement of cardiac output by multifrequency bioimpedance." Thesis, Queensland University of Technology, 2003.
Find full text
50
Guo, Chuan. "Biosensitive Functionalised Silicon Surfaces: towards Biosensitive Field-Effect-Transistors." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/9476.
Full textAbstract:
Electrical impedance spectroscopy (EIS) is a method that characterizes the electrical properties of a system of interest and provides a non destructive method for studying its structure and function. In this study, EIS was used to determine the electrical properties and physical structure of the formation of Self-assembled monolayers (SAMs) of biological materials on silicon surfaces. The electrical properties and physical structures of the interaction of human antibodies with carboxylic acid groups attached to highly and low doped n-type silicon (111) are presented. The specific binding test of anti-human antibodies with human antibody modified silicon surfaces were analysed by EIS and confirmed by X-ray photoelectron spectroscopy (XPS). Plasma polymers were the second major topic in this research. They were used as alternative linkers to attach biomolecules to the silicon substrate. Compared to the self-assembled monolayers technology, plasma polymers provided higher protein coverage and required simpler preparative processes. EIS results revealed the changes in the electric properties after each step of the attachment process and binding of ligands. XPS measurements and wetting tests confirmed the EIS results. The results in this thesis show that EIS is a fast and reliable detection method and sensitive enough to detect small changes on the molecular monolayer level. Measurements can be performed directly without requiring any special treatment. The SAMs or plasma coated polymers immobilized directly on the silicon surfaces provides a platform for antibody immobilization in biosensor development that can be tailored to detect antigen-antibody binding. The coupling of the biomolecules on low doped silicon surface induced a field effect inside the silicon. This field effect was dependent on the charge of the biomolecules. This would therefore allow the construction of an actual experimental BioFET that could detect the antigen-antibody interactions.