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1
Solano, B., S. Rolt i D. Wood. "Thermal and mechanical analysis of an SU8 polymeric actuator using infrared thermography". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 222, nr 1 (1.01.2008): 73–86. http://dx.doi.org/10.1243/09544062jmes676.
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In the current paper, report the detailed thermomechanical analysis of a polymeric thermal actuator integrated in a microelectromechanical systems microgripper, is reported. The inclusion of an actuator design which eliminates completely the parasitic resistance of the cold arm improves considerably the thermal efficiency of the system and enables large displacements at lower input voltages and operating temperatures than reported previously. Two different microgrippers built using a trilayer polymer/metal/polymer combination of SU8/gold/SU8 have been modelled, fabricated, and tested. As opposed to standard models, heat transfer by conduction to the ambient as well as between adjacent beams has been modelled. A semi-empirical approach for the calculation of conductive heat transfer coefficients has also been provided. The analysis combines simulations with electrical, deflection, and spatially resolved temperature measurements. The latter was carried out using infrared thermography, its use in polymeric actuators reported here for the first time. The good agreement between the models and the experimental data support the conclusions of the basic analytical model, i.e. thermal losses are dominated by two conduction mechanisms (into the ambient and between the hot and cold arms), and encourage its use for qualitative thermal design assessment and optimization.
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Viannie, Leema Rose, G. R. Jayanth, V. Radhakrishna i K. Rajanna. "Fabrication and Nonlinear Thermomechanical Analysis of SU8 Thermal Actuator". Journal of Microelectromechanical Systems 25, nr 1 (luty 2016): 125–33. http://dx.doi.org/10.1109/jmems.2015.2490485.
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Sheikhbahaie, Reza, Aria Alasty i Hassan Salarieh. "Design, Modeling and Optimization of a Novel Two DOF Polymeric Electro-Thermal Micro-Actuator". Applied Mechanics and Materials 307 (luty 2013): 112–16. http://dx.doi.org/10.4028/www.scientific.net/amm.307.112.
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In this paper, design, simulation and optimization of a novel electrothermally-activated polymeric microactuator capable of generating combination of bidirectional lateral and rotational motions are presented. The composite structure of this actuator is consisted of a symmetric meandered shape silicon skeleton, a SU8 thermal expandable polymer and a thin film chrome layer heater. This actuator is controlled by applying appropriate voltages on its four terminals. With the purpose of dimension optimization, a numerical parametric study is executed. The modeled actuator which is 1560 μm long, 156 μm wide and 30 μm thick, demonstrates a remarkable lateral displacement of 23 μm at power consumption of 38 mW and a considerable rotation of about 7.5° at the same power consumption but with excitation of different terminals.
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Mitrev, Rosen, Todor Todorov, Andrei Fursov i Borislav Ganev. "Theoretical and Experimental Study of a Thermo-Mechanical Model of a Shape Memory Alloy Actuator Considering Minor Hystereses". Crystals 11, nr 9 (14.09.2021): 1120. http://dx.doi.org/10.3390/cryst11091120.
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The paper presents a theoretical and experimental investigation of a thermo-mechanical model of an actuator composed of a shape memory alloy wire arranged in series with a bias spring. The developed mathematical model considers the dynamics of the actuator in the thermal and mechanical domains. The modelling accuracy is increased through the developed algorithm for modelling the minor and sub minor hystereses, thus removing the disadvantages of the classical model. The algorithm improves the accuracy, especially when using pulse-width modulation control, for which minor and sub minor hystereses are likely to occur. Experimental studies show that the system is very sensitive, and there are physical factors whose presence cannot be considered in the mathematical model. The experimental research has shown that setting constant values of the duty cycle is impossible to obtain a stable value of displacement and force. The comparison between the developed mathematical model results and the experimental results shows that the differences are acceptable. The improved modelling serves as a basis for designing such actuators and creating an improved automatic feedback control system to maintain a given displacement (force) or trajectory tracking.
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Goteea, Bimal Jeet, Qianjun Zhang i Wei Dong. "A Compact Electromagnetic Dual Actuation Positioning System with a 10 mm Range and Nanometer Resolution". Actuators 12, nr 3 (21.03.2023): 132. http://dx.doi.org/10.3390/act12030132.
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In this manuscript, a compact electromagnetic dual actuation positioning system (CEDAPS) based on the Lorentz force principle that features a 10 mm range and nanometer-scale resolution with flexure guides is presented. Firstly, the stiffness of the flexure mechanism is modelled. Secondly, based on it, the primary coil is designed, and from its performance, a suitable secondary coil is made to compensate for the deficiency of the primary actuation subsystem. The characteristics of the forces generated by these coils are also evaluated by an electromagnetic FEA simulation. Thirdly, a control scheme is presented that combines the performances of these two actuators, and finally, a prototype is fabricated to evaluate the performance. The results show a 10 nm resolution for a 10 mm (±5 mm) stroke with low sub-micron sinusoidal tracking errors and nanometer accuracy for step tracking under the proposed control scheme. The thermal properties of the system are also presented.
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Maré, Jean-Charles. "Practical Considerations in the Modelling and Simulation of Electromechanical Actuators". Actuators 9, nr 4 (25.09.2020): 94. http://dx.doi.org/10.3390/act9040094.
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The work reported here was aimed at improving the practical efficiency of the model-based development and integration of electromechanical actuators. Models are proposed to serve as preliminary design, virtual prototyping, and validation. The first part focuses on the early phases of a project in order to facilitate the identification of modelling needs and constraints, and to build a top-level electromechanical actuator model for preliminary studies and sub-specification. Detailed modelling and simulation are then addressed with a mixed view on the control, power capability, and thermal balance. Models for the power chain are firstly considered by focusing on the key practical issues in modelling the electric motor, power electronics, and mechanical power transmission. The same logic is applied to the signal and control chain with practical considerations concerning the parameters of the controller, its digital implementation, the sensors, and their signal conditioning. Numerous orders of magnitude are provided to justify the choices made and to facilitate decision-making for and through simulation activities.
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Torres, David, LaVern Starman, Harris Hall, Juan Pastrana i Sarah Dooley. "Design, Simulation, Fabrication, and Characterization of an Electrothermal Tip-Tilt-Piston Large Angle Micromirror for High Fill Factor Segmented Optical Arrays". Micromachines 12, nr 4 (12.04.2021): 419. http://dx.doi.org/10.3390/mi12040419.
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Micro-electromechanical system (MEMS) micromirrors have been in development for many years, but the ability to steer beams to angles larger than 20° remains a challenging endeavor. This paper details a MEMS micromirror device capable of achieving large motion for both tip/tilt angles and piston motion. The device consists of an electrothermal actuation assembly fabricated from a carefully patterned multilayer thin-film stack (SiO2/Al/SiO2) that is epoxy bonded to a 1 mm2 Au coated micromirror fabricated from an SOI wafer. The actuation assembly consists of four identical actuators, each comprised of a series of beams that use the inherent residual stresses and coefficient of thermal expansion (CTE) mismatches of the selected thin films to enable the large, upward, out-of-plane deflections necessary for large-angle beamsteering. Finite element simulations were performed (COMSOL v5.5) to capture initial elevations and tip/tilt motion displacements and achieved <10% variance in comparison to the experiment. The measured performance metrics of the micromirror include tip/tilt angles of ±23°, piston motion of 127 µm at sub-resonance, and dynamics characterization with observed resonant frequencies at ~145 Hz and ~226 Hz, for tip/tilt and piston motion, respectively. This unique single element design can readily be scaled into a full segmented micromirror array exhibiting an optical fill-factor >85%, making it suitable for optical phased array beam control applications.
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Acharya, Govatsa, Fredrik Dehlin, Sara Bortot i Ignas Mickus. "INVESTIGATION OF A SELF-ACTUATED, GRAVITY-DRIVEN SHUTDOWN SYSTEM IN A SMALL LEAD-COOLED REACTOR". EPJ Web of Conferences 247 (2021): 07007. http://dx.doi.org/10.1051/epjconf/202124707007.
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Passive safety systems in a nuclear reactor allow to simplify the overall plant design, beside improving economics and reliability, which are considered to be among the salient goals of advanced Generation IV reactors. This work focuses on investigating the application of a self-actuated, gravity-driven shutdown system in a small lead-cooled fast reactor and its dynamic response to an initiating event. The reactor thermal-hydraulics and neutronics assessment were performed in advance. According to a first-order approximation approach, the passive insertion of shutdown assembly was assumed to be influenced primarily by three forces: gravitational, buoyancy and fluid drag. A system of kinematic equations were formulated a priori and a MATLAB program was developed to determine the dynamics of the assembly. Identifying the delicate nature of the balance of forces, sensitivity analysis for coolant channel velocities and assembly foot densities yielded an optimal system model that resulted in successful passive shutdown. Transient safety studies, using the multi-point dynamics code BELLA, showed that the gravity-driven system acts remarkably well, even when accounting for a brief delay in self-actuation. Ultimately the reactor is brought to a sub-critical state while respecting technological constraints.
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Naserbakht, Sepideh, Andreas Naesby i Aurélien Dantan. "Stress-Controlled Frequency Tuning and Parametric Amplification of the Vibrations of Coupled Nanomembranes". Applied Sciences 9, nr 22 (12.11.2019): 4845. http://dx.doi.org/10.3390/app9224845.
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Noninvasive tuning of the mechanical resonance frequencies of suspended parallel nanomembranes in various monolithic arrays is achieved by piezoelectric control of their tensile stress. Parametric amplification of their thermal fluctuations is shown to be enhanced by the piezoelectric actuation and amplification factors of up to 20 dB in the sub-parametric oscillation threshold regime are observed.
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Arnesano, Marco, Andrea Calvaresi, Filippo Pietroni, Lorenzo Zampetti, Sara Magnani, Oscar Casadei i Gian Marco Revel. "A Sub-Zonal PMV-Based HVAC and Façade Control System for Curtain Wall Buildings". Proceedings 2, nr 15 (27.08.2018): 1138. http://dx.doi.org/10.3390/proceedings2151138.
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This paper presents an experimental test room in a curtain wall building where an innovative monitoring and control system was implemented and tested. The proposed solution is composed by an IR-based comfort sensor that measures the PMV (Predicted Mean Vote) index for 2 room’s sub-zones and provides the optimal air temperature set-points. The overall control system includes a distributed sensors and actuators network, also embedded into the façade modules, to measure indoor and outdoor parameters and to regulate fan-coils, windows opening and shadings with a sub-zonal approach. Initial results turn out to provide an energy saving of about 20% with an improvement of thermal/visual comfort and IAQ conditions.
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Arnesano, Marco, Andrea Calvaresi, Filippo Pietroni, Lorenzo Zampetti, Sara Magnani, Oscar Casadei i Gian Marco Revel. "A Sub-Zonal PMV-Based HVAC and Façade Control System for Curtain Wall Buildings". Proceedings 2, nr 15 (27.08.2018): 1596. http://dx.doi.org/10.3390/proceedings2151596.
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This paper presents an experimental test room in a curtain wall building where an innovative monitoring and control system was implemented and tested. The proposed solution is composed by an IR-based comfort sensor that measures the PMV (Predicted Mean Vote) index for 2 room’s sub-zones and provides the optimal air temperature set-points. The overall control system includes a distributed sensors and actuators network, also embedded into the façade modules, to measure indoor and outdoor parameters and to regulate fan-coils, windows opening and shadings with a sub-zonal approach. Initial results turn out to provide an energy saving of about 20% with an improvement of thermal/visual comfort and IAQ conditions.
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Warthmann, Alexander, Daniel Wölki, Henning Metzmacher i Christoph van Treeck. "Personal Climatization Systems—A Review on Existing and Upcoming Concepts". Applied Sciences 9, nr 1 (22.12.2018): 35. http://dx.doi.org/10.3390/app9010035.
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To accomplish the current climate goals of the federal republic of Germany, energy efficiency within the building and automotive sector must improve considerably. One possible way to reduce the high amount of energy required for heating, ventilation, and air-conditioning (HVAC) is the introduction of personal climatization systems in combination with the extension of the standardized room air temperature range. Personal systems allow improvements of climatic conditions (heating, cooling, and air quality) within sub-areas of the room instead of conditioning an entire room air volume. In this regard, personal systems are perfectly suitable for locations with local air-conditioning focal points, such as open-plan offices and vehicle cabins, where they substantially improve the energy efficiency of the entire system. This work aims to summarize previously conducted research in the area of personal climatization systems. The investigated local thermal actuators comprise fans for the generation of air movement, ventilators for the improvement of the air quality within the respiratory area of persons, water-conditioned panels for the climatization of persons via longwave radiation and conduction, radiant heaters, and combinations of the systems. Personal systems are superior to mixing ventilation regarding the improvement of the perceived air quality and thermal comfort. Furthermore, the introduced overview shows that personal climatization systems are generally more energy-efficient than conventional air-conditioning and facilitates the extension of the indoor air temperature corridor of the HVAC. Table fans and climatized seats are highly effective in connection with the improvement of personal thermal comfort. The performance of the overwhelming majority of applied personal environmental control systems is user-controlled or depends on a predefined load profile, which is generally defined person independent. Single studies reveal that effectively controlled automated systems have a similar thermal impact on a user’s thermal comfort as user-controlled ones. The implementation of an automated control system is feasible by using novel approaches such as the so-called human-centered closed loop control-platform (HCCLC-platform). The latter contains a central data server which allows asynchronous, bi-directional communication between multi-modal sensor data, user feedback systems, thermal actuators and numerical calculation models used to assess the individual thermal comfort of a person. This enables a continuous and holistic reflection of the thermal situation inside a room and the estimation of the corresponding impact on an individual’s thermal comfort. Considering the measured and simulated thermal state of a single person, the described system is capable of determining body-part-specific energy requirements that are needed to keep the overall thermal comfort level of an individual person on a high level.
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Kwac, Lee Ku, Jae Yeol Kim i Young Tae Cho. "Motion and Environment Error Compensation for Ultra-Precision Lathe". Key Engineering Materials 297-300 (listopad 2005): 2339–44. http://dx.doi.org/10.4028/www.scientific.net/kem.297-300.2339.
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Recently, the demand for Ultra-precision products is rapidly increasing, especially in such industries as semi-conductors, computers, aerospace, and precision machinary. Ultra-precision processing is also extremely needed for NT in the field of mechanical engineering. Lately, together with drastic advancement of electronic and photonics industry, the need of Ultra-precision processing is increased in the manufacturing of various kernel parts, which are connected with these industrial fields. Especially, motion accuracy to nanometers is required in order in stroke of hundreds millimeters according as the diameter of the processed object great and the processing accuracy rises. In this case, the response speed absolute delay due to inertial mass of the moving parts is very large. Therefore, real-time motion error compensation becomes the barest necessity. In this paper, we used ultra-precision cutting unit (UPCU) to cope with the problem. A special UPCU was designed and tested to obtain sub-micrometer from accuracy in diamond turning of flat surfaces. The thermal growth spindle error was compensated in real time using the UPCU driven by piezoelectric actuator along with a laser encoder displacement sensor.
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Qiao, Qifeng, Haoyang Sun, Xinmiao Liu, Bowei Dong, Ji Xia, Chengkuo Lee i Guangya Zhou. "Suspended Silicon Waveguide with Sub-Wavelength Grating Cladding for Optical MEMS in Mid-Infrared". Micromachines 12, nr 11 (26.10.2021): 1311. http://dx.doi.org/10.3390/mi12111311.
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Mid-infrared (MIR) photonics are generating considerable interest because of the potential applications in spectroscopic sensing, thermal imaging, and remote sensing. Silicon photonics is believed to be a promising solution to realize MIR photonic integrated circuits (PICs). The past decade has seen a huge growth in MIR PIC building blocks. However, there is still a need for the development of MIR reconfigurable photonics to enable powerful on-chip optical systems and new functionalities. In this paper, we present an MIR (3.7~4.1 μm wavelength range) MEMS reconfiguration approach using the suspended silicon waveguide platform on the silicon-on-insulator. With the sub-wavelength grating claddings, the photonic waveguide can be well integrated with the MEMS actuator, thus offering low-loss, energy-efficient, and effective reconfiguration. We present a simulation study on the waveguide design and depict the MEMS-integration approach. Moreover, we experimentally report the suspended waveguide with propagation loss (−2.9 dB/cm) and bending loss (−0.076 dB each). The suspended waveguide coupler is experimentally investigated. In addition, we validate the proposed optical MEMS approach using a reconfigurable ring resonator design. In conclusion, we experimentally demonstrate the proposed waveguide platform’s capability for MIR MEMS-reconfigurable photonics, which empowers the MIR on-chip optical systems for various applications.
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Verma, Kamlesh, Debashis Ghosh, Rajeev Marathe i Avnish Kumar. "Efficient Embedded Hardware Architecture for Stabilised Tracking Sighting System of Armoured Fighting Vehicles". Defence Science Journal 69, nr 3 (30.04.2019): 208–16. http://dx.doi.org/10.14429/dsj.69.14414.
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A line-of-sight stabilised sighting system, capable of target tracking and video stabilisation is a prime requirement of any armoured fighting tank vehicle for military surveillance and weapon firing. Typically, such sighting systems have three prime electro-optical sensors i.e. day camera for viewing in day conditions, thermal camera for night viewing and eye-safe laser range finder for obtaining the target range. For laser guided missile firing, additional laser target designator may be a part of sighting system. This sighting system provides necessary parameters for the fire control computer to compute ballistic offsets to fire conventional ammunition or fire missile. System demands simultaneous interactions with electro-optical sensors, servo sensors, actuators, multi-function display for man-machine interface, fire control computer, logic controller and other sub-systems of tank. Therefore, a complex embedded electronics hardware is needed to respond in real time for such system. An efficient electronics embedded hardware architecture is presented here for the development of this type of sighting system. This hardware has been developed around SHARC 21369 processor and FPGA. A performance evaluation scheme is also presented for this sighting system based on the developed hardware.
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Katta, Miranji, R. Sandanalakshmi, M. Narendra Kumar i Ch Jaya Prakash. "Static and Dynamic Analysis of Carbon Nano Tube Cantilever for Nano Electro Mechanical Systems Based Applications". Journal of Computational and Theoretical Nanoscience 17, nr 5 (1.05.2020): 2151–56. http://dx.doi.org/10.1166/jctn.2020.8862.
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The cantilever is the most basic form of the MEMS and NEMS-based applications. It may include actuators and sensors in multiple domains for the detection of deflections due to change in mass and charge from atomic to sub-atomic levels. The main constraints in the real-time environment for sensing applications are good sensitivity and selectivity along with good response time and wide dynamic range. CNTs (Carbon Nano Tubes) possess excellent electrical characteristics with good mechanical strength like elasticity, flexibility, tensile strength and good thermal conductivity. These properties make use of CNTs in NEMS that gives rise to good sensing platforms. In this paper we propose, design and analysis of CNT based Cantilever structure using FEM to determine the change in deflection due to varying load under static analysis. Similarly from dynamic analysis change in resonance frequency for change in thickness of Cantilever is performed. From the experimental results using COMSOL simulation, it is observed that the CNT based Cantilever deflection sensitivity is 9.85 x 10-8 m under maximum stress of 6.71 x 10-9 N/m2. From the dynamic analysis, resonant frequency occurs at 1.8 x 107 Hz for 10 nm thickness and for 50 nm is 7.5 x 107 Hz respectively.
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Kovaľ, Vladimír. "High aspect ratio lead zirconate titanate tube structures: I. Template assisted fabrication - vacuum infiltration method". Processing and Application of Ceramics 6, nr 1 (2012): 37–42. http://dx.doi.org/10.2298/pac1201037k.
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Polycrystalline Pb(Zr0.52Ti0.48 )O3 (PZT) microtubes are fabricated by a vacuum infiltration method. The method is based on repeated infiltration of precursor solution into macroporous silicon (Si) templates at a sub-atmospheric pressure. The pyrolyzed PZT tubes of a 2-?m outer diameter, extending to over 30 ?m in length were released from the template using a selective isotropic-pulsed XeF2 reactive ion etching of silicon. Free-standing microtubes, partially anchored at the bottom of the Si template, were then crystallized in pure oxygen atmosphere at 750 ?C for 2 min using a rapid thermal annealer. The perovskite phase of the final PZT tubes was confirmed by X-ray diffraction (XRD) analysis. The XRD spectrum also revealed a small amount of the pyrochlore phase in the structure and signs of possible fluoride contamination caused most likely by the XeF2 etching process. The surface morphology was examined using scanning electron microscopy. It was demonstrated that the whole surface of the pore walls was conformally coated during the repeated infiltration of templates, resulting in straight tubes with closed tips formed on the opposite ends as replicas of the pore bottoms. These high aspect ratio ferroelectric structures are suggested as building units for developing miniaturized electronic devices, such as memory storage (DRAM trenched) capacitors, piezoelectric scanners and actuators, and are of fundamental value for the theory of ferroelectricity in systems with low dimensionality.
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Haub, Michael, Martin Bogner, Thomas Guenther, André Zimmermann i Hermann Sandmaier. "Development and Proof of Concept of a Miniaturized MEMS Quantum Tunneling Accelerometer Based on PtC Tips by Focused Ion Beam 3D Nano-Patterning". Sensors 21, nr 11 (30.05.2021): 3795. http://dx.doi.org/10.3390/s21113795.
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Most accelerometers today are based on the capacitive principle. However, further miniaturization for micro integration of those sensors leads to a poorer signal-to-noise ratio due to a small total area of the capacitor plates. Thus, other transducer principles should be taken into account to develop smaller sensors. This paper presents the development and realization of a miniaturized accelerometer based on the tunneling effect, whereas its highly sensitive effect regarding the tunneling distance is used to detect small deflections in the range of sub-nm. The spring-mass-system is manufactured by a surface micro-machining foundry process. The area of the shown polysilicon (PolySi) sensor structures has a size smaller than 100 µm × 50 µm (L × W). The tunneling electrodes are placed and patterned by a focused ion beam (FIB) and gas injection system (GIS) with MeCpPtMe3 as a precursor. A dual-beam system enables maximum flexibility for post-processing of the spring-mass-system and patterning of sharp tips with radii in the range of a few nm and initial distances between the electrodes of about 30–300 nm. The use of metal–organic precursor material platinum carbon (PtC) limits the tunneling currents to about 150 pA due to the high inherent resistance. The measuring range is set to 20 g. The sensitivity of the sensor signal, which depends exponentially on the electrode distance due to the tunneling effect, ranges from 0.4 pA/g at 0 g in the sensor operational point up to 20.9 pA/g at 20 g. The acceleration-equivalent thermal noise amplitude is calculated to be 2.4–3.4 mg/Hz. Electrostatic actuators are used to lead the electrodes in distances where direct quantum tunneling occurs.
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Vasiliev, A. A., A. S. Lipilin, A. M. Mozalev, A. S. Lagutin, A. V. Pisliakov, N. P. Zaretskiy, N. N. Samotaev, A. V. Sokolov i S. A. Soloviev. "Gas Sensors Based on Ceramic MEMS Structures Made of Anodic Alumina and Yttria Stabilized Zirconia Films". Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2012, CICMT (1.09.2012): 000528–34. http://dx.doi.org/10.4071/cicmt-2012-wp33.
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The application of thin ceramic films for the fabrication of MEMS devices enables the extension of their working temperature range up to 600°C, a decrease in heating power consumption, and a very considerable decrease in production cost of sensors and actuators based on this technology. These advantages are very important for the application of gas sensors under harsh environmental conditions, in autonomous and wireless sensor networks. The methods of the fabrication of MEMS platforms for metal oxide semiconductor and thermocatalytic gas sensors, fast thermometers, and flowmeters based on yttria stabilized zirconia (YSZ) and alumina membranes for gas sensors are described. Alumina membranes stable up to 800°C have thickness of about 12 microns and are produced by anodic oxidation of aluminum foil in diluted oxalic acid followed by high-temperature annealing. YSZ membrane with the same thickness is made by slip casting with consequent annealing under mechanic load. Platinum heaters are deposited onto the surface of the membrane by magnetron sputtering through metallic shadow mask. Perfect adhesion of platinum to ceramic material permits us to avoid the application of adhesive sub-layers, and, therefore, improves long-term stability of the heater at high temperature. The sensor chip has a shape of triangle cut by laser beam; the heater meander is located in the vertex of triangle. This approach simplifies the technology of the fabrication of the platform and decreases power necessary for the heating of the sensing layer up to working temperature of 400 – 600°C. It is shown that the application of such triangle shaped membranes permits a decrease in power consumption of the MEMS working at 450°C down to ~ 40 mW at continuous and down to < 1 mW at pulse heating of gas sensor with duty cycle of 1 %. Thermal response time of the microheater is of about 80 ms.
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Lee, Sung-Chang, i Brian D. Strom. "Characterization of Thermally Actuated Pole Tip Protrusion for Head-Media Spacing Adjustment in Hard Disk Drives". Journal of Tribology 130, nr 2 (3.03.2008). http://dx.doi.org/10.1115/1.2842248.
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The effect of thermomechanically actuated pole tip protrusion on adhesive forces is characterized through model and experiment. The roughness of a thermomechanically actuated region is characterized by atomic force microscopy. Using the extracted roughness parameters and estimated apparent area associated with thermal actuation, the intermolecular forces at the head-disk interface (HDI) are calculated using the ISBL (improved sub-boundary lubrication) code. Both roughness and nominal area of contact are found to be significant factors determining adhesive forces. The adhesive forces for various HDI designs—including thermal actuation—are also characterized experimentally in situ using commercial hard disk drive samples. The experimental results are found to be consistent with the model calculations and imply certain advantages for thermally actuated HDI designs. However, the experiments also raise concerns regarding the field application of the technology.
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Goldberg, Kenneth A., i Kyle T. La Fleche. "Thickness dependence of piezo-bimorph adaptive mirror bending". Review of Scientific Instruments 94, nr 7 (1.07.2023). http://dx.doi.org/10.1063/5.0154575.
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A new generation of adaptive x-ray optics (AXO) is being installed on high-coherent-flux x-ray beamlines worldwide to correct and control the optical wavefront with sub-nm precision. These ultra-smooth mirrors achieve high reflectivities at glancing angles of incidence and can be hundreds of mm long. One type of adaptive x-ray mirror relies on piezoelectric ceramic strips which are segmented into channels and actuated to induce local, longitudinal bending, generating one-dimensional shape changes in the mirror substrate. A recently described mirror model uses a three-layer geometry with parallel actuators on the front and back surfaces of a thicker mirror substrate. By analogy to a solved problem in the thermal actuation of a tri-metal strip, we show that the achievable bending radius varies approximately as the square of the substrate thickness. We provide an analytic solution and simulate bending using a finite-element model.
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Chen, Sinuo, Zhiwei Shi, Xi Geng, Zijie Zhao, Zhen Chen i Quanbing Sun. "Study of the transient flow structures generated by a pulsed nanosecond plasma actuator on a delta wing". Physics of Fluids, 21.09.2022. http://dx.doi.org/10.1063/5.0111858.
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The transient flow structures produced by a pulsed nanosecond plasma actuator and the mechanism by which they are generated are investigated experimentally and through simulations for the case of flow control on a non-slender delta wing. Phase-locked particle image velocimetry reveals a phenomenon in which, after each discharge pulse, two sub-vortices are generated in sequence and move along the shear layer regardless of the angle of attack, and this is confirmed by hot-wire anemometry. However, at high actuation frequencies ( F+ = fc/ U∞ {greater than or equal to} 6.435), this phenomenon of double sub-vortices is not observed, and only one sub-vortex is generated per period. The results of pressure measurements indicate that each sub-vortex gives rise to a distinct pressure fluctuation on the wing surface. Numerical simulations reveal a number of residual heats resulting from plasma thermal effects in the shear layer, each of which turns out to induce a corresponding sub-vortex. At low actuation frequencies ( F+ {less than or equal to} 4.29), there is a division of the initial residual heat into two independent residual heats and hence double sub-vortices per period, whereas at high actuation frequencies ( F+ {greater than or equal to} 6.435), residual heats from two consecutive periods merge into one, resulting in just one sub-vortex per period, which provides an explanation for the experimentally observed flow behavior.
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Vyawahare, Saurabh, Suresh Sitaula, Sujitha Martin, Dvin Adalian i Axel Scherer. "Combining Shape Memory Alloys and Microfluidic Chips on Printed Circuit boards". Journal of Medical Devices 2, nr 2 (1.06.2008). http://dx.doi.org/10.1115/1.2934387.
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Integrated multi-layer fluidic chips, with hundreds of elastomeric valves, are useful in immunoassays, protein crystallization, cell culture and several other applications. Although the devices are micro-scale, because valves are actuated pneumatically, each chip requires a relatively large pneumatic control system for operation. Fulfilling the great promise of microfluidics, for instance building throwaway, portable, massively parallel, point-of-care diagnostic systems is unlikely until there is a solution for actuating micro-valves electrically. We introduce a combination of materials—shape memory alloys (SMAs) and elastomersto solve this problem. SMAs offer among the highest work per unit volume of any actuator, and elastomers have the ability to absorb the energy and return the SMA to its original configuration, while providing electric and thermal insulation. Using this marriage of materials, with PDMS (elastomer) and Ni/Ti wires (SMA), we built electrically activated micro-fluidic valves, peristaltic pumps and multiplexers. The first generation valve design needs 50 to 250 mA current in the on state, with power requirements of about 0.5 W. It can hold back >1 atmosphere of pressure and run for thousands of cycles, actuating at sub-second speeds. The dead volume is <1 nano-liter. Crucially, these devices are assembled on printed circuit boards, like conventional electronic components. Thus, the technology used in assembling electronics is applicable to assembling fluidic chips, and both electronics and fluidics can be integrated on one platform for biomedical applications.
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Wang, Xuefeng, i Chang Liu. "Development of Hybrid MEMS/FIB Processes and Applications of Three-pronged Active Nanotweezers For Manipulation of Nano Objects". MRS Proceedings 983 (2006). http://dx.doi.org/10.1557/proc-983-0983-ll08-09.
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AbstractWe report recent development of a three-probe micromachined nanomanipulator for manipulation and in-situ characterization of nanomaterials in scanning electron microscope (SEM). The nanomanipulator consists of three independent probes having thermal bimetallic actuators and nanoscopic end-effectors. Nanoscale end-effectors with sub-100-nm spacing are created using focused ion beam (FIB) milling to directly interface with nanoscopic objects (e.g., nanotubes, nanowires). Handling of individual carbon nanotubes (CNTs) was successfully realized with the nanomanipulator in an SEM.
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Di Bartolomeo, Marco, Davide Di Battista i Roberto Cipollone. "Experimentally Based Methodology to Evaluate Fuel Saving and CO <sub>2</sub> Reduction of Electrical Engine Cooling Pump during Real Driving". SAE International Journal of Engines 16, nr 5 (9.03.2023). http://dx.doi.org/10.4271/03-16-05-0041.
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<div>Engine thermal management (ETM) is a promising technology that allows the reduction of harmful emissions and fuel consumption when the internal combustion engine (ICE) is started from a cold state. The key technology for ETM is the decoupling of the cooling pump from the crankshaft and the actuation of the pump independently. In this article, an electric engine cooling pump has been designed through a novel experimentally based procedure and operated on a vehicle equipped with an advanced turbocharged gasoline engine, particularly interesting for its hybridization potential. In the first phase, a dedicated experimental campaign was conducted off board on an engine identical to the one equipped in the vehicle to assess the characteristics of the cooling circuit and the reference pump performances. The experimental data have been used to design an electric pump with a best efficiency point (BEP) located in a region more representative of the real operating conditions faced by the vehicle during real driving. Once prototyped, the electric pump has been compared to the reference mechanical one on a real driving mission profile whose parameters have been experimentally evaluated. The comparison was made in the same operating conditions of flow rate and the pressure head acting on the revolution speed of the prototype to focus the attention on the effect of the different design choices made possible by the electric actuation. The procedure can evaluate the pump-related fuel consumption, whatever the real vehicle speed profile and the actuation of the pump. The results show that in a driving cycle with urban, extra-urban, and highway phases, the electric pump absorbs 66% less power compared to the mechanical one, which translates into a 0.55 gCO<sub>2</sub>/km specific emission reduction. This demonstrates the validity of the novel design procedure together with the benefits of the electric actuation.</div>