Dissertations / Theses on the topic 'Membranes suspendues'

Le but de la Nano- Opto- Mécanique et Electronic à base de graphène est d'utiliser des membranes de graphène en suspension comme blocs de construction pour aborder le couplage entre l'optique, la mécanique et l'électronique dans ce nouveau matériau. Avec un module d'Young similaire à celui du diamant (1 TPA), le graphène est une membrane extrêmement rigide, légère et mince (epaaisseur de seulement un atome) qui peut supporter son propre poids sans effondrement ou la rupture lorsqu'il est suspendu. Ces membranes, intégrées dans des dispositifs mécaniques, peuvent être actionnés à partir de DC jusqu'à des fréquences de vibration mécaniques très élevées (GHz). En outre, le graphène est un gaz d'électrons 2D exposé pour lequel une porte électrostatique tunes considérablement la densité de porteurs de charge et ses propriétés optiques. Last but not least, il offre une architecture unique pour effectuer la fonctionnalisation physico-chimiques et obtenir des matériaux hybrides combinant les propriétés particulières des espèces chimisorbées avec ceux du graphène
The aim of the Graphene Nano- Opto- Mechanics and Electronics is to use suspended graphene membranes as building blocks to address the coupling of optics, mechanics and electronics in this novel material. With a Young modulus similar to that of diamond (1 TPa), graphene is an extremely stiff, light and atomically thin membrane that can withstand its own weight without collapsing or breaking when suspended. Such membranes, integrated as mechanical devices, can be actuated from DC up to very high mechanical vibration frequencies (GHz). Moreover, graphene is an exposed 2D electron gas for which an electrostatic gate dramatically tunes the charge carrier density and its optical properties. Last but not least, it provides a unique architecture to perform physico-chemical functionalization and obtain hybrid materials combining the peculiar properties of adsorbed and chemisorbed species with the graphene ones

Les travaux de recherche présentés dans cette thèse s'inscrivent dans des travaux menés au C2N. Mon sujet de thèse porte sur le transport de chaleur dans des matériaux dit bidimensionnels. Ces matériaux ont des très fortes liaisons dans deux dimensions de l'espace et de très faibles liaisons (de type Van der Waals) dans la troisième dimension. Cette asymétrie a de fortes conséquences en terme de propriétés thermiques. Tout d'abord, la conductivité thermique de ces matériaux va s'en trouver anisotrope. Dans le plan avec les fortes liaisons, celle-ci va être très élevée tandis que dans la direction perpendiculaire, elle peut atteindre les plus petites valeurs observées dans des solides. En outre, le régime de transport de la chaleur dévie du régime classique suivant la loi de Fourier. Ce sont les raisons qui nous ont poussé à s'intéresser aux propriétés thermiques de ces matériaux. Ma thèse s'est décomposée en deux parties.Dans un premier temps, je me suis intéressée au transport thermique dans du hexagonal Boron Nitride (hBN) qui est un matériau bidimensionel avec une très grande conductivité thermique et une très faible conductivité électrique. J'ai suspendu des matériaux bidimensionnels entre deux poutres chauffantes espacées de 8 microns. À l'aide de mesures de température réalisées avec un spectromètre Raman, j'ai pu déterminer une conductivité thermique de 1650 ±550 W.m⁻¹.K⁻¹ dans une structure de hBN à basse température (aux alentours de -50 °C). Pour ce faire, j'ai comparé les gradients de température expérimentaux mesurés à travers les structures aux gradients de température que j'ai déterminés à l'aide de simulations Comsol. Cette valeur de 1650 ±550 W.m⁻¹.K⁻¹ est une valeur record pour ce matériau et provient du fait que le hBN utilisé est isotopique.J'ai confirmé la procédure expérimentale en réalisant la même expérience sur un échantillon de graphite donnant une conductivité thermique en adéquation avec celles obtenues dans la littérature. Lors de mesures similaires sur un autre échantillon, j'ai observé des gradients de température incohérents avec la loi de Fourier. Cette mesure a été faite autour de la température ambiante. Nous en avons déduit que l'échantillon se trouvait dans un régime où le transport thermique ne suivait plus le modèle classique. Dans un second temps, je me suis intéressée à la possibilité de réaliser de très grands gradients de température à travers des matériaux bidimensionnaux. En fabriquant des hétérostructures de hBN¹¹/MoS₂/WSe₂/hBN¹⁰ chauffées avec un laser de haut en bas, j'ai pu étudier le transport thermique dans la direction des liaisons de type Van der Waals. Une différence en température de 75 °C a été observée sur une distance de 1,5 nm entre le MoS₂ et WSe₂. Cette valeur est extrêmement importante. Cette grande différence en température est à relier à la faible conductance thermique d'interface entre ces deux matériaux et à la forte puissance appliquée à l'échantillon. En utilisant un modèle issu de la littérature comportant une dépendance en conductance thermique d'interface, j'ai pu simuler des gradients de températures au sein de matériaux chauffés par un laser. Ceci m'a permis de simuler des spectres Raman similaires à ceux mesurés. J'en ai déduit des conductances thermiques d'interface environ quatre fois plus faibles entre le MoS₂ et WSe₂ que mesurées dans la littérature (inférieures à 5 MW.m⁻¹.K⁻¹ à opposer à 9 MW.m⁻¹.K⁻¹. J'ai aussi examiné la différence de transport thermique en fonction de l'angle entre ces mêmes matériaux
The research work presented in this manuscript is part of the technological monitoring efforts led at the C2N in the MAT2D team. My subject is about heat transport in so-called two-dimensional materials. These materials have very strong bonds in two dimensions of space and fragile bonds (Van der Waals bonds) in the third dimension. This asymmetry has important thermal property repercussions: the thermal conductivity of these materials is anisotropic. In the strong-bondings plane, the thermal conductivity is very high, whereas in the perpendicular direction, it reaches the smallest values observed in solids. Moreover, the heat transport regime deviate from the classical Fourier's Law regime. These are the reasons that drive us to study these properties. The manuscript is constituted of two parts. Firstly, I investigated thermal transport in a two-dimensional material: hexagonal Boron Nitride (hBN). This material is interesting because it is a high thermal conductor and a high electrical insulator. I had to innovate to suspend two-dimensional materials between two heatable cantilevers spaced by 8 microns. Using temperature measurements with a Raman spectrometer, I was able to determine a thermal conductivity of 1650 ±550 W.m⁻¹.K⁻¹ in an suspended hBN structure at low temperature (around -50°C). I used extit{Comsol} simulations to determine temperature gradients across the structure comparable to the experimental results. It allows me to determine the in-plane thermal conductivity of the two-dimensional material. The 1650 ±550 W.m⁻¹.K⁻¹ value is a record value for this material and comes from different parameters. One is the fact that the hBN is isotopic. I confirmed the experimental procedure by doing the same experiment on a sample of Graphite. It gives a thermal conductivity that is coherent with those obtained in the literature. I observed temperature gradients inconsistent with Fourier's law (even around ambient temperature) through similar measurements on another sample. We deduced that the sample was in a non-classical heat regime. Secondly, I investigated the possibility of achieving very large temperature gradients across samples of two-dimensional materials. By heating a thin sample of suspended hBN, I observed a gradient of 210° along 8 microns. By fabricating hBN¹¹/MoS₂/WSe₂/hBN¹⁰ heterostructures heated with a laser, I was also able to study thermal transport in the direction of the Van der Waals bonds. A temperature difference of 75°C was observed within 1.5 nm between MoS₂ and WSe₂. This value is extremely high. This significant temperature difference can be linked to the low thermal conductance at the interface between these two materials and the high optical power applied to the structure. Using a model from the literature with an interface thermal conductance dependence, I could simulate temperature gradients within a material heated by a laser. This enabled me to simulate Raman spectra of MoS₂ similar to those measured. I deduced low interface thermal conductances between MoS₂ and WSe₂ (less than 5 MW.m⁻¹.K⁻¹ whereas in the literature, it was measured equal to 9 MW.m⁻¹.K⁻¹). I also examined the difference in thermal transport as a function of the angle between these same materials and observed a slight difference of temperature of the top material depending of the angle

Ce travail présente une étude par diffusion micro-Raman de membranes de graphène suspendu.La spectroscopie Raman est présentée comme un outil rapide et peu invasif pour estimer les contraintes natives dans du graphène suspendu et est utilisée pour en sonder quantitativement la déflexion, induite soit par une différence de pression d’air soit électrostatiquement. Dans des bulles de graphène pressurisées, une analyse minutieuse des intensités et fréquences des principaux modes Raman permet une détermination tout-op que de la topographie de la bulle, du module de Young et des paramètres de Grüneisen du graphène. Une grille électrostatique offre une manière élégante d’introduire à la fois des contraintes et du dopage dans le graphène. Des mesures Raman permettent une détermination précise de la déflection induite par la force électrostatique (jusqu’à l’effondrement irréversible), en très bon accord avec un modèle électromécanique
This work presents a micro-Raman scattering study of undoped suspended graphene membranes. Raman spectroscopy is introduced as a fast and minimally invasive tool to estimate sample dependent built-in strain in suspended graphene, and is further employed to quantatively probe the membrane deflection, which may be induced either by an air pressure difference or electrostatically. In pressurized graphene blisters, an all-optical determination of the blister topography, the Young’s modulus and the Grüneisen parameters of graphene is achieved by a thorough analysis of the intensity and frequency of the main Raman modes. Electrostatic gating offers an elegant way to simultaneously strain and dope graphene. Raman measurements allow an accurate determination of the electrostatically-induced graphene deflection (up to irreversible collapse), in very good agreement with an electromechanical model

Les travaux présentés dans ce mémoire traite du développement et de l'optimisation de nouvelles filières technologiques d'élaboration de circuits micro-ondes suspendus sur membrane diélectrique. Cette élaboration passe par l'étude physique, mécanique et électrique de nouveaux matériaux susceptibles de répondre aux cahiers des charges. Nous proposons la filière technologique basée sur la fabrication de membranes épaisses à partir des dépôts par plasma. L'intérêt majeur de cette technologie est d'améliorer la fiabilité mécanique du composant. Les résultats en terme de caractérisation fréquentielle montre un bon accord avec la filière développée auparavant et qui est dédiée essentiellement à la fabrication de circuits micro-ondes de surface assez faible sur membrane mince. Dans un second volet, nous proposons un banc de test pour la caractérisation mécanique des matériaux. Dans cette optique, un système de gonflement de membrane suspendue sous pression différentielle a permis de tester les propriétés mécaniques du nitrure de silicium. Les contraintes résiduelles et le module d'Young du matériau sont extraits. La dernière partie concerne la réalisation d'une antenne à émission surfacique de type Yagi-Uda sur membrane diélectrique. La miniaturisation et les technologies de micro-usinage volumique du silicium ont permis la réduction des dimensions, et surtout l'utilisation de ce type d'antennes en haute fréquence. Nous décrivons un nouveau procédé de gravure de silicium adapté à la fabrication de ce type d'antenne. La caractérisation électrique des structures fabriquées est en accord avec les résultats de simulation électrique. De plus, des simulations mécaniques des structures fabriquées sont présentées afin de clarifier l'origine des déformations des dispositifs.

This thesis reports research activity on suspended graphene membranes. Scientific results in the form of peer-reviewed publications are presented, along with supporting information to provide context, detailed experimental procedures, and recommendations of future work. The four papers cover a wide variety of topics, but are linked by common experimental sample fabrication techniques. Understanding the mechanical properties of suspended graphene membranes is crucial to the development of graphene nano-electromechanical devices. In the first presented paper, PeakForce QNM (quantitative nanomechanical mapping) atomic force microscopy imaging was used to rapidly map the nanomechanical properties of a range of suspended graphene membranes. The force-displacement behaviour of monolayer graphene extracted from the peak force imaging map was found to be comparable to that taken using standard nanoindentation. By fitting to a simple elastic model, the two-dimensional elastic modulus was measured at around 350Nm-1, corresponding to a Young's modulus of around 1 TPa. The second paper examines the near-IR light-matter interaction for graphene integrated cavity ring resonators based on silicon-on-insulator (SOI) racetrack waveguides. Fitting of the cavity resonances from the predicted transmission spectra reveal the real part of the effective refractive index for graphene, neff = 2.23 ± 0.02 and linear absorption coefficient, alphagTE = 0.11 ±0.01dB micro metre-1. The evanescent nature of the guided mode coupling to graphene at resonance depends strongly on the height of the graphene above the cavity, which places limits on the cavity length for optical sensing applications. Twisted-bilayer graphene (tBLG) exhibits van Hove singularities in the density of states that can be tuned by changing the twisting angle θ. In the third paper, θ-defined tBLG was produced and characterized using optical reflectivity and resonance Raman scattering. This represents the first reported fabrication of a rationally designed (twist engineered) tBLG structure. The θ-engineered optical response is shown to be consistent with persistent saddlepoint excitons. Separate resonances with Stokes and anti-Stokes Raman scattering components can be achieved due to the sharpness of the two-dimensional saddle-point excitons, similar to what has been previously observed for one-dimensional carbon nanotubes. The excitation power dependence for the Stokes and anti-Stokes emissions indicate that the two processes are correlated and that they share the same phonon. Nano-patterned and suspended graphene membranes find applications in electronic devices, filtration and nano-pore DNA sequencing. However, the fabrication of suspended graphene structures with nanoscale features is challenging. In the fourth and final paper, the direct patterning of suspended membranes consisting of a graphene layer on top of a thin layer of hexagonal boron nitride which acts as a mechanical support is demonstrated for the first time, using a highly focused electron beam to fabricate structures with extremely high resolution within the scanning transmission electron microscope. The boron nitride support enables the fabrication of stable graphene geometries which would otherwise be unachievable, by preventing intrinsic strain in graphene membranes from distorting the patterned features after areas are mechanically separated. Line cuts with widths below 2 nm are reported. It is also demonstrated that the cutting can be monitored in-situ utilising electron energy loss spectroscopy (EELS).

This thesis presents a novel architecture for a sensing element fabricated from a conducting polymer and a bioderived membrane. The thin film device provides controlled, selective ion transport from a chemical concentration and produces measurable electrical signals, ion storage, and small scale actuation. A chemical gradient applied across a bioderived membrane generates ion flow through protein transporters in the presence of a gating signal. A conducting polymer undergoes ion ingress/egress in the presence of an electrical and chemical potential, which causes a change on the polymers conformal backbone. A ligand (or) voltage gated protein in the bioderived membrane results in ion transport through the bioderived membrane. Integrating the two electroactive materials provides a unique architecture which takes advantage of their similarities in ionic function to produce a device with controlled and selective ion transport. The chemoelectromechanical device is one that couples chemical, electrical, and mechanical potentials through number of ions, dielectric displacement, and strain. The prototype consists of a stacked thin conducting polymer film and bioderived membrane which form three aqueous chambers of varying ionic concentrations. The top chamber contains an electrolytic solution, and the bottom chamber contains deionized water adjacent to the conducting polymer. The current that passes through a conducting polymer for an applied electrical signal is based on the level of doping/undoping and therefore can be used as a method of sensing protein function in the sensing element. This architecture results in a sensing element applicable in real time chemical sensors, volatile organic compound detectors, and bioanalytical sensors. The conducting polymer layer is formed from polypyrrole (PPy) doped with sodium dodecylbenzenesulfonate (NaDBS), and the bilayer lipid membrane is formed from 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) reconstituted with the protein alamethicin. The magnitude of current required to span a 175 µm pore was empirically found to be 326.5 A/cm2 and is based on electrode condition, electrode surface area, pyrrole concentration, and electrical potential. A micron-scale pore through a silicon substrate is spanned by a thin PPy(DBS) layer, forming a bridge which supports the bioderived membrane. The bioderived membrane is reconstituted with alamethicin, a voltage-gated protein extracted from trichoderma viride. Ion transport experiments were performed to characterize the PPy(DBS) layer and the bioderived membrane and are represented as electrical equivalents for subsequent analysis. The equivalent impedance of polypyrrole was calculated to be 1.7847±0.1735Ωcm2 and capacitance was calculated to be 1.2673±0.1823µF/cm2. The equivalent impedance of a bioderived membrane was calculated to be 1.654±1.9894MΩcm2, capacitance was calculated to be 1.1221± 0.239µF/cm2, and alamethicin resistance was calculated to be 1.025± 0.7228MΩcm2. Thus, using impedance measurements in the conducting polymer layer, it is proposed that a scaled up sensing element can be fabricated using the suspended polypyrrole supported bioderived membrane.

The recent demonstration of strong interactions between optical force and mechanical motion of an optomechanical structure has led to the triumphant result of mechanical ground-state cooling, where the quantum nature of a macroscopic object is revealed. Another intriguing demonstration of quantum physics on a macroscopic level is the measurement of the Casimir force which is a manifestation of the zero- point energy. An interesting aspect of the Casimir effect is that the anharmonicity of the Casimir potential becomes significant when the separation of microscale objects is in the sub-100nm regime. This regime is readily accessible by many of the realized gradient-force-based optomechanical structures. Hence, a new avenue of probing the Casimir effect on-chip all-optically has become available. We propose an integrated optomechanical platform, consisting of a suspended photonic crystal membrane evanescently coupled with a silicon-on-insulator substrate, for (i) measuring the Casimir force gradient and (ii) counteracting the attractive force by exerting a resonantly enhanced repulsive optical gradient force. This thesis first presents the full characterization of the optomechanical properties of the system in vacuo. The interplay of the optical gradient force (optomechanical coupling strength \(g_{om}/2\pi=- 66GHz/nm\)) and the photothermal force manifested in the optical spring effect and dynamic backaction is elucidated. Static displacement by the repulsive force of 1nm/mW is also demonstrated. In the second part of the thesis, the nonlinear mechanical signatures upon a strong coherent drive are reported. By resonantly driving the photonic crystal membrane with a piezo-actuator and an optical gradient force, we observed mechanical frequency mixing, mechanical bistability and non-trivial interactions of the Brownian peak with the driving signal. Finally we present our recent progress in establishing electro- static control of individual photonic crystal membranes to reduce and calibrate the electrostatic artifact which plagues Casimir measurements. The results discussed in this thesis point towards an auspicious future of a complete realization of a Casimir optomechanical structure and novel applications with nonlinearity afforded by the Casimir force and the optical gradient force.
Engineering and Applied Sciences

Les nonlinéarités dans les systèmes nanomécaniques peuvent provenir d’effets dispersif ou dissipatif et ce dans divers systèmes (résistifs, inductifs et capacitifs). Au-delà de l’intérêt fondamental pour tester la réponse dynamique d’un système non-linéaire à plusieurs dégrées de libertés, les nonlinéarités de tels systèmes ouvre la voie vers des capteurs nanomécanique et le traitement du signal. Le résonateur nanomécanique dont la réponse nonlinéaire est étudié, est une membrane suspendue à cristal photonique bidimensionnel utilisée comme miroir déformable. Sa faible masse et sa haute réflectivité en font un candidat idéal pour l’électro-opto-mécanique. L’actuation d’une telle membrane dans le domaine fréquentiel du MHz est rendu possible par des électrodes inter-digitées en dessous de la membrane assurant ainsi l’uniformité de la force d’actuation sur cette dernière. La fabrication de telles structures est basée sur l’intégration hétérogène 3D.La force électrostatique qui s’applique sur la membrane induit des non-linéarités mécaniques avec notamment un effet bistable, des résonances superharmoniques et des résonances stochastiques.La membrane est mise en mouvement par un potentiel électrique V(t) = Vdc + Vac cos(w.t), où Vdc est l’amplitude du courant continu, Vac l’amplitude du courant alternatif à la fréquence d’excitation w;. Le système se comporte alors comme une capacité de sorte que la force qui s’applique sur la membrane varie de manière quadratique avec la tension appliquée. Selon la tension DC ou AC, le comportement de la structure est différent. L’augmentation de la tension DC induit une augmentation de la tension de polarisation sur le matériau qui par conséquent modifie la fréquence propre de la membrane. Tandis que l’augmentation de la tension AC cause l’augmentation de l’amplitude des oscillations de la membrane pouvant aller jusqu’à atteindre le régime non-linéaire.Dans une première série de mesure, la membrane est excitée à la résonance avec une fréquence w; égale à la fréquence du mode mécanique fondamental wm. A partir de la réponse fréquentielle du système, il est possible d’identifier différents modes mécaniques de la membrane sondé optiquement. Pour une excitation plus importante, il est possible d’observer des effets de bistabilité mécanique. Ces non-linéarités sont dues à l’élongation au niveau des points d’ancrage de la membrane.La méthode la plus commune pour agir sur la membrane est l’excitation proche de la résonance fondamentale. Cependant la technique de la résonance superharmonique peut également être utilisée. Cela consiste à appliquer la fréquence d’excitation w; à une fréquence égale à wm/n où n est un entier. La possibilité d’utiliser cette technique est fortement dépendante des nonlinéarités présentes dans le système. Ainsi, l’existence d’une résonance super harmonique à wm/n résulte de la présence d’une nonlinéarité d’ordre n. Dans une seconde série de mesure, un balayage des résonances superharmoniques en fonction de la fréquence et de la puissance a été réalisé en modulant la tension à la fréquence wm/n et en enregistrant la réponse de la membrane autour de wm. Il a été ainsi possible d’observer des résonances superharmoniques allant de n=2 jusqu’à 8. Il a également été possible d’obtenir l’évolution de la phase le long des résonances et ce pour toutes celles observées.Dans une dernière série de mesure, nous utilisons la nonlinéarité présente pour observer des effets de résonance stochastique. L’idée est d’amplifier un signal de faible amplitude (basse fréquence) en injectant du bruit (haute fréquence) dans le système nonlinéaire. Dans le cas de notre système, nous avons été capables d’observer des résonances stochastiques à la fois en amplitude et en phase. Une étude comparative de ces deux régimes est détaillée. Le fait de pouvoir observer la résonance stochastique en phase peut permettre d’envisager la réalisation de communications codées en phase
Nonlinearities in nanomechanical systems can arise from various sources such as spring and damping mechanisms and resistive, inductive, and capacitive circuit elements. Beyond fundamental interests for testing the dynamical response of discrete nonlinear systems with many degrees of freedom, non-linearities in nanomechanical devices, open new routes for nanomechanical sensing, and signal processing.The nonlinear response of a nanomechanical resonator consisting in a suspended photonic crystal membrane acting as a deformable mirror has been investigated. The low-mass and high reflectivity of suspended membranes pierced by a two-dimensional photonic crystal, makes them good candidates as electro-optomechanical resonator. Actuation of the membrane motion in the MHz frequency range is achieved via interdigitated electrodes placed underneath the membrane. The choice of these electrodes is due to the fact they are able to uniformly actuate these membranes. The processing of such platforms relies on 3D-heterogenous integration process.The applied electrostatic force induces mechanical non-linearities, in particular bistability, superharmonic resonances and stochastic resonance.The membrane is actuated by an electric load V(t) = Vdc + Vac cos(w.t), where Vdc is the DC polarization voltage, Vac the amplitude of the applied AC voltage, and w; the excitation frequency. The system acts as a capacitive system and thus the force applied on the membrane varies as a quadratic function of the applied voltage. Application of either DC or AC voltages can have different implications. Increasing the DC voltage increases the polarizing voltage on the material which in turn causes modulation of the eigenfrequency of the membranes. While an increase in the periodic AC voltage causes the membrane to oscillate more, pushing the system towards non-linear regime.In a first series of experiments, the membrane is actuated resonantly, with an excitation frequency w; equal to the fundamental mechanical modes frequency wm. From the frequency response spectra of the system it was possible to identify different mechanical modes of these membranes via optical measurements. For increased actuation voltages, bistability effects are observed with two different behaviors (spring hardening or softening). The mechanical nonlinearities due to stretching at the clamping point dominate the resonator dynamics.The most commonly used method to act upon the membrane is the primary-resonance excitation, in which the frequency of the excitation is tuned closed to the fundamental natural frequency of the nanostructure. Superharmonic resonance can also be implemented. It consists in applying an excitation frequency w; equal to wm/n, with n being integer. Existence of these superharmonic resonances is highly dependent on the non-linearity of the system. For example existence of n-th order non-linearity results in presence wm/n superharmonic resonance. In a second series of experiments, frequency-power sweep for superharmonic resonance has been performed, by modulating the electric load at a frequency wm/n and recording the response of the membrane at the fundamental frequency wm. High-order superharmonic resonances are observed with n=2 up to 8. Under superharmonic excitation, the control of the phase across the resonance has been shown for every observed resonance.In the next set of experiments, we used the nonlinearity existing in the system to perform stochastic resonance. The idea of stochastic resonance is amplification of a weak signal (with low frequency) by means of noise injected (higher frequency) in a nonlinear system. For our system we were able to achieve stochastic resonance with both amplitude and phase noise. A comparative study between these two schemes was also done in details. The idea of observing stochastic resonance in phase is very interesting as it opens doors to realize phase encoded communications

Serving as key players in cell signaling, nearly all cells in the human body contain GPCRs. As the largest and most diverse superfamily of proteins in the human body, GPCRs are linked to some of the most prevalent current disease states including cardiovascular disease, type II diabetes, and various types of cancers. The development of new biosensors capable of simple, specific, sensitive, high-throughput screenings of the ligand-binding events of GPCRs are crucial to the diagnosis and maintenance of such diseases. To this end, this research is focused on the development of a novel biosensor platform incorporating ICCRs reconstituted into BLMs. Although ICCRs have been expressed previously in oocytes and HEK293 cells, no occurrence of cell-free expression has yet been performed. The advantages of such a platform include the specificity and real-time measurement capabilities of GPCRs, the innate sensitivity of electrophysiological ion channel flux measurements, and the simplified cellular mimicking of the BLM and cell-free expression. The majority of the presented research was based in the molecular cloning of M2Kir6.2, an ICCR incorporating a muscarinic acetylcholine receptor (M2), from Xenopus oocyte vector pGH2 into cell-free expression vector pT7CFE1-CGST-HA-His. Much optimization of the cloning procedure (PCR, digestion, and ligation) was necessary involving studies into polymerase fidelity, inclusion of DpnI for degradation of methylated DNA, and ligation parameter alterations in time, temperature, and insert:vector ratios. It was discovered that Deep VentR polymerase was beneficial to preventing mutations within the sequence of M2Kir6.2 during PCR, DpnI was capable of degrading unwanted residual M2Kir6.2 pGH2, and ligation performance was optimal using a 1:1 (insert:vector) ratio and reaction time and temperature of 18 h and 4 °C, respectively. With the successful ligation of M2Kir6.2 into cell-free expression vector pT7, expression of the ICCR via cell-free expression lysate kit was performed with direct reconstitution into a micropipette suspended BLM attempted. Five reconstitution trials were performed with electrophysiological single-channel recording results suggesting ICCR insertion based on ion channel currents of ~ 3 pA and mean open-times of ~ 3 ms observed corresponding to literature values for native Kir6.2 channels. Additionally, a Western blot analysis of the cell-free expression mixture contained products with molecular weights corresponding to monomer (~ 100 kDa) and tetramer (~ 400 kDa) constructs of M2Kir6.2. With the successful optimization of the M2Kir6.2 pT7 cloning procedure, this procedure can be used in future cloning attempts with similar ICCR constructs, such as D2Kir6.2. Although preliminary electrophysiological results suggest ICCR expression and BLM reconstitution, further work needs to be done in controlling the amount of ICCR insertion and optimizing BLM stability. Additionally, in order to confirm the functionality of both M2 and Kir6.2 ligand dose response curves must be performed. The evidence supporting ICCR expression and direct reconstitution into suspended BLMs via cell-free protein expression is both exciting and promising. Not only has this research involved the first cell-free expression of M2Kir6.2 but also has great benefits to the further development of such novel ligand-binding biosensor platforms.

Ce travail de thèse porte sur des composants à cristaux photoniques (CP) bidimensionnels réalisés dans des matériaux à base d’InP pour un fonctionnement dans le domaine 1,55 μm. Au sein du CP, la périodicité de la constante diélectrique génère une bande interdite photonique, domaine de fréquence dans lequel la propagation des modes optiques est interdite. L’introduction de défauts dans le CP permet à certains modes optiques localisés d’exister. De telles structures peuvent alors être utilisées comme brique élémentaire d’un circuit intégré photonique. Nous avons étudié des adaptateurs de mode et des lasers monofréquences ainsi que des guides d’onde sur membrane InP. Les CP sont ici un réseau de trous fabriqués à l'aide de la gravure ionique réactive associée à un plasma à couplage inductif. Dans un plasma Cl2/Ar optimisé, nous avons obtenu une profondeur de gravure de 2,9 μm pour des trous de 250 nm diamètre. Nous avons montré que la présence de N2 dans un plasma contenant du chlore renforce la gravure anisotrope et supprime la rugosité des surfaces gravées, et que l’addition de BCl3 permet d’augmenter la verticalité des trous. Le plasma BCl3/N2 a permis d’obtenir les meilleurs profils et états de surface et une profondeur gravée de 1 μm. Plusieurs géométries d’adaptateurs de mode à CP. Ont été étudiées et leurs spectres de transmission ainsi que la divergence du mode émergent ont été caractérisés et comparés avec les résultats de simulation. La meilleure géométrie conduit à une amélioration de l’efficacité de transmission d’un facteur 4. Les guides W1 sur membrane InP présentent des pertes de propagation de 25 dB/cm pour des fréquences situées sous la ligne de lumière
This PhD work focuses on two-dimensional photonic crystals (PhC) devices based on InP materials for application around 1. 55 µm wavelength. PhC is a periodic structure in dielectric constant and is characterized by photonic band gap, a frequency domain in which the light propagation is inhibited for certain directions. Introducing defects in the periodicity offers another manner for light guiding and photon localization, which may provide a platform for photonic integrated circuits. The investigated devices include PhC taper waveguides and multiple-constricted-waveguide lasers on InP substrate, and PhC channel defect waveguides on InP suspended membrane. The perforated PhC structures are realized using reactive ion etching technique associated with inductive coupled plasma. A Cl2/Ar plasma has been optimized and demonstrated an etch depth of 1. 9~2. 9 µm for 110~250 nm-diameter holes. We have demonstrated that the addition of N2 into chlorine-containing plasmas can enhance the anisotropic etching and suppress the etched surfaces roughness. In addition, we have shown that adding BCl3 augments the feature verticality. Extremely smooth etched sidewall surfaces are obtained when the etching is performed under the BCl3/N2 plasma; in which an etch depth of 1 µm can be achieved. Several contour geometries of PhC tapers are studied and their transmission spectra and beam divergences are measured and compared with the simulation results. The transmission efficiency can be enhanced by a factor of 4 owing to the proper taper design. As for suspended membrane, a propagation loss of 25 dB/cm has been obtained for W1 PhC waveguide while operating below the air-light line

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1992.
Includes bibliographical references (leaves 109-116).
by Jeffrey Yen Pan.
Ph.D.

Le polytype cubique du carbure de silicium (3C-SiC) est un matériau très prometteur pour les applications MEMS. En plus de sa tenue mécanique et chimique, il peut être épitaxié sur des substrats Si de faible coût. De plus, l'hétéroépitaxie multiple, c’est-à-dire quand on empile plusieurs couches Si et 3C-SiC peut ouvrir des pistes pour de nouveaux dispositifs à base de 3C-SiC. Vue la complexité de développer de telles hétérostructures, nous avons procédé à l'amélioration de la qualité de chaque couche séparément. De plus, nous avons mené une étude approfondie sur la nature des défauts dans chaque couche. Après le développement de l'hétérostructure complète, nous avons procédé à la fabrication de microstructures à base de cet empilement. Nous présentons une méthode inédite pour former des membranes de 3C-SiC auto-supportées. Cette technique simplifie considérablement le procédé de fabrication de membranes tout en réduisant le temps de fabrication et le coût. En outre, elle aide à surmonter plusieurs problèmes techniques
Due to its outstanding physico-chemical properties, the cubic polytype of silicon carbide (3C-SiC) gained significant interest in several fields. In particular, this material emerged as a potential candidate to replace Si in MEMS devices operating in harsh environment. The development of 3C-SiC/Si/3C-SiC heterostructures on top of Si substrate can pave the road towards original and novel MEMS devices profiting from the properties of the 3C-SiC. However, such epitaxial system suffers from wide range of defects characterizing each layer. Thus, we first tried to improve the quality of each layer in this heterostructure. This was achieved relying on two levers; (i) the optimization of the growth parameters of each layer and (ii) the understanding of the nature of defects present in each layer. These two key points combined together allowed an in-depth understanding of the limit of improvement of the overall quality of this heterostructure. After the development of the complete heterostructure, the fabrication of 3C-SiC microstructures was performed. Furthermore, we presented an unprecedented method to form free-standing 3C-SiC membranes in-situ during its growth stage. This novel technique is expected to markedly simplify the fabrication process of suspended membranes by reducing the fabrication time and cost

Ce travail de thèse porte sur des composants à cristaux photoniques (CP) bidimensionnels réalisés dans des matériaux à base d'InP pour un fonctionnement dans le domaine 1,55 µm. Au sein du CP, la périodicité de la constante diélectrique génère une bande interdite photonique, domaine de fréquence dans lequel la propagation des modes optiques est interdite. L'introduction de défauts dans le CP permet à certains modes optiques localisés d'exister. De telles structures peuvent alors être utilisées comme brique élémentaire d'un circuit intégré photonique. Nous avons étudié des adaptateurs de mode et des lasers monofréquences ainsi que des guides d'onde sur membrane InP.

Les CP sont ici un réseau de trous fabriqués à l'aide de la gravure ionique réactive associée à un plasma à couplage inductif. Dans un plasma Cl2/Ar optimisé, nous avons obtenu une profondeur de gravure de 2,9 µm pour des trous de 250 nm diamètre. Nous avons montré que la présence de N2 dans un plasma contenant du chlore renforce la gravure anisotrope et supprime la rugosité des surfaces gravées, et que l'addition de BCl3 permet d'augmenter la verticalité des trous. Le plasma BCl3/N2 a permis d'obtenir les meilleurs profils et états de surface et une profondeur gravée de 1 µm.

Plusieurs géométries d'adaptateurs de mode à CP ont été étudiées et leurs spectres de transmission ainsi que la divergence du mode émergent ont été caractérisés et comparés avec les résultats de simulation. La meilleure géométrie conduit à une amélioration de l'efficacité de transmission d'un facteur 4. Les guides W1 sur membrane InP présentent des pertes de propagation de 25 dB/cm pour des fréquences situées sous la ligne de lumière.

Ce mémoire de thèse aborde la caractérisation expérimentale du transfert thermique à l’échelle nanométrique dans des matériaux compatibles avec les procédés de la micro-électronique. Pour cela deux techniques de caractérisation sont appliquées chacune à deux différents systèmes, le silicium mésoporeux irradié et les membranes de silicium suspendues. La première technique de caractérisation est la thermométrie micro-Raman. La puissance du laser chauffe l'échantillon exposé. La détermination de la conductivité thermique nécessite la modélisation de la source de chaleur par la méthode des éléments finis. Dans les cas considérés la modélisation de la source de chaleur repose sur différents paramètres qui doivent être soigneusement déterminés. La seconde technique de caractérisation est la microscopie à sonde locale (d’acronyme anglais SThM), basée sur le principe de la microscopie à force atomique (d’acronyme anglais AFM). Utilisée en mode actif, la sonde AFM est remplacée par une sonde résistive de type Wollaston qui est chauffée par effet Joule. Utilisée en mode AFM contact, cette technique permet une excitation thermique locale du matériau étudié. La détermination de la conductivité thermique nécessite l'analyse de la réponse thermique de la sonde au moyen d'échantillons d'étalonnage et également via la modélisation dans le cas des géométries complexes. L'effet de la position de la pointe sur le transfert de chaleur entre la pointe et l'échantillon est étudié. Une nouvelle méthode de découplage entre le transfert de chaleur entre la pointe et l'échantillon, respectivement à travers l'air et au contact, est proposée pour la détermination de la conductivité thermique des géométries complexes. Les résultats obtenus avec les deux techniques pour les échantillons de silicium mésoporeux irradiés à l’aide d’ions lourds dans le régime électronique sont en bon accord. Ils montrent la dégradation de la conductivité thermique du silicium mésoporeux suite à une augmentation dans la phase d’amorphe lorsque la dose d’irradiation croît. Les résultats obtenus sur les membranes de silicium suspendues montrent une réduction de la conductivité thermique de plus de 50 % par rapport au silicium massif. Lorsque la membrane est perforée périodiquement afin de réaliser une structure phononique de période inférieure à 100 nm, cette réduction est approximativement d’un ordre de grandeur. Un chapitre introduisant un matériau prometteur à base de silicium pour observer des effets de cohérence phononique conclut le manuscrit
This PhD thesis deals with the experimental characterization of heat transfer at the nanoscale in materials compatible with microelectronic processes. Two characterization techniques are applied to two different systems, irradiated mesoporous silicon and suspended silicon membranes. The first characterization technique is micro-Raman thermometry. The laser power heats up the exposed sample. The determination of the thermal conductivity requires the modeling of the heat source using finite element simulations. The modeling of the heat source relies on different parameters that should be carefully determined. The second characterization technique is Scanning Thermal Microscopy (SThM), an Atomic Force Microscopy (AFM)-based technique. Operated in its active mode, the AFM probe is replaced by a resistive Wollaston probe that is heated by Joule heating. Used in AFM contact mode, this technique allows a local thermal excitation of the studied material. The determination of the thermal conductivity requires the analysis of the thermal response of the probe using calibration samples and modeling when dealing with complicated geometries. The effect of the tip position on heat transfer between the tip and the sample is studied. A new method decoupling the heat transfer between the tip and the sample, at the contact and through air, is proposed for determining the thermal conductivity of complicated geometries. The results obtained from the two techniques on irradiated mesoporous silicon samples using heavy ions in the electronic regime are in good agreement. They show a degradation of the thermal conductivity of mesoporous silicon due to the increase in the amorphous phase while increasing the ion fluence. The results obtained on suspended silicon membrane strips show a decrease in the thermal conductivity of more than 50 % in comparison to bulk silicon. When perforated into a phononic structure of sub-100 nm period, the membrane thermal conductivity is about one order of magnitude lower than the bulk. A chapter introducing a promising silicon-based material for the evidence of phonon coherence concludes the manuscript

Etude des performances de ce systeme de filtration sur membrane en utilisant des polluants de differentes natures (solutes organiques, particules en suspension) representants ceux contenus dans une eau reelle plus complexe

Les canaux ioniques sont des protéines membranaires permettant le transport ionique au travers des membranes biologiques. Du fait de leur omniprésence dans l'organisme, ils représentent une classe de cibles thérapeutiques encore actuellement peu exploitée du fait de limitations expérimentales dans leur étude. La mesure électrique de l'activité des canaux ioniques au sein de bicouches biomimétiques reconstituées in vitro permettrait de répondre à ces limitations. Cependant, il n'existe actuellement pas de système satisfaisant au cahier des charges complet pour de telles analyses : stabilité et pureté de la bicouche, faible niveau de bruit, insertion rapide des canaux ioniques, intégration dans un dispositif fluidique, possibilité de mener une caractérisation optique simultanée. L'objectif de ces travaux de thèse était d'évaluer dans quelle mesure l'utilisation d'un substrat SOI (Silicon On Insulator) comprenant des nanopores pourrait permettre de répondre à tous ces critères. Des nanopores de diamètre compris entre 10 nm et 160 nm ont été réalisés à partir d'un substrat SOI. Une cellule fluidique transparente est utilisée pour l'adressage fluidique. Cette cellule permet d'autre part la double caractérisation électrique et optique. Les propriétés électriques en milieu liquide du dispositif ont été étudiées et permettent de dégager des perspectives d'amélioration. La double caractérisation électrique et optique est démontrée au moyen d'expériences de capture de nanoparticules fluorescentes sur les nanopores. Enfin, des premiers résultats prometteurs d'obtention d'une bicouche lipidique suspendue sont présentés
Ion channels are membrane proteins responsible for ion transport across biological membranes. Due to their ubiquity, they are promising drug targets but are not yet fully exploited as such due to experimental restrictions in their study. Electrical measurement of ion channels activity within in vitro artificial lipid bilayers would enable to overcome these restrictions. However, there is not yet a system satisfying all the requirements for ion channels studies: stability and purity of the lipid bilayer, low noise level, fast insertion of ion channels, fluidic integration, ability to perform simultaneous optical characterization. The aim of this phD was to assess in which extent the use of an SOI (Silicon On Insulator) substrate bearing nanopores could satisfy all these requirements. 10 nm to 160 nm diameter nanopores were fabricated in an SOI substrate and characterized. A transparent fluidic cell was used for fluidic addressing. This transparent cell allows combined electrical and optical characterization. Electrical properties of the device in aqueous environment were studied, allowing to bring out improvement prospects. The combined electrical and optical characterization was demonstrated with fluorescent nanoparticle trapping experiments on the nanopores. Finally, promising results about the formation of a free-standing lipid bilayer are presented

碩士
國立交通大學
電子工程系所
92
Infra-Red sensors are promising components in the field of MEMS. The technologies in MEMS can be divided into bulk micromaching and surface micromaching. Among them, surface micromaching is easier to be integrated and more compatible with integrated circuits(IC). Another advantage of surface micromaching is its high fill factor. Thus, surface micromaching is believed to be the niche of the ULSI generation. In this work, we use the surface micromaching to fabricate suspended membranes for Infra-Red sensors (microbolometers). In order to avoid melting aluminum interconnects within the integrated circuit, all processes were done at low temperature. Furthermore, the computer simulation was used to predict and discuss all possible factors which may deteriorate the device performance. With these considerations, a good suspended membrane for microbolometer applications, with low residual stress and processed at low temperature was successfully realized.

Cheng, Zhenzhou.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2013.
Includes bibliographical references.
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstract also in Chinese.

碩士
國立清華大學
工程與系統科學系
98
We perform molecular dynamic simulations to understand the behavior and mechanism of AFM indentation through a lipid bilayer which is suspended by hydrophobic substrate on a nano pore. This work starts from the study of basic properties of lipid bilayer. By simulating lipid bilayer in bulk with solvent environment, we calculate membrane thickness, area per lipid, and order parameter. Three states are found from low temperature to high temperature: tilted gel state, interdigitated gel state, and liquid state. Besides main transition which is from gel state to liquid state, we also observe transition from tilted gel state to interdigitated gel state. The work in phase transition consists with many previous works, which demonstrate the reality of our model and setup. The second part of the work is AFM indentation of suspended lipid bilayer. We build the system with suspended lipid bilayer on a nano pore. After a long period of equilibrium, bilayer is indented by AFM probe. The shape of the side wall of substrate is a straight cliff with 90 degree at its corners. The probe is a half sphere located at the center of the pore. From the contact between the lipid bilayer and the probe, we conclude 5 stages: 1. the pressed lipid bilayer bends to arched curve, while the edges of lipid bilayer slide on the side wall of substrate. 2. The edges of lipid bilayer reach the end of pore on the side wall and stop sliding, while bending continuously proceeds. 3. The breaking at bottom monolayer happens in the center region, which cause chaotic distribution in the region. 4. Lipids at the region of monolayer breaking reform into interdigitated gel structure. 5. The fracture happens at the conjunction between transformed region and non-transformed region due to incongruence between the two regions. The sliding mechanism is mentioned first time and really surprises us. This mechanism eliminates the stress concentration between side wall of substrate and edge of lipid bilayer, and avoids the early breaking at the contact surface. At the end, we calculate the spring constant, maximum force on probe, and maximum depth of indentation. We find the data are in good agreement with experimental result. This further verifies the validity of our study. In the research, we employ some new methods such as Quasi-2D and phantom solvent which can be used in other researches in this field.

碩士
朝陽科技大學
建築及都市設計研究所
91
With suspension membrane structure conduct and actions a kind of new structural form , there are advantage and weaknesses of its self. Among them, its build is novel, the weight is light , carrying out more easily to across the span greatly and than the other the form of structure, the comprehensiveness have no the heavy space of the stanchion, but it belong to the flexible structure again at the same time, comparing easily under the influence of wind rose, rain, snow of outer force lading, and the strain is heavy, so adopt right of design method, process of the procedure more accurately and in rational construction method of the procedure and reasonable more accurately. Besides, how to guarantee that the final shaping of the structure can in accordance with the design the phase, in addition to it is more careful while designing, and plus each organiztion to match with more consistently, know how to handle its membrane material and the characteristic of structures, and make use of the assistance of the computer program, after completed the work and usage stage, return to need to have the certain examination procedure to guarantee, and carry on the pertinent maintenance to repair of the measures, then can carry out the technique application of the optimization, presenting to blend the building build, emerge the behavior of structure, and have the comfort, safety and economy membrane structures building.

碩士
元智大學
化學工程學系
91
In this paper, the characteristics of untrasonic waves like cavitation were applied to modify the processes of ultrafilitration (UF) for the separation of W/O emulsions from external phase. This is because the flux decline and serious fouling phenomena occurs in the ultrafiltration of W/O emulsions. The resistance-in-series model was used to determine the role of operating variables in this system. Firstly, we used ultrasound to prepare W/O emulsions, and the optimal conditions were 100 mL of internal phase, 3 vol% of surfactant concentration, the ratio of internal phase to oil phase was 2 : 1, and 93 watt of operating power. Within 5 mins, ultrosound upped the volume of W/O emulsions to 100 %. In the stirred cell, ultrasound can improve the flux during ultrafiltration of PEI solutions and W/O emulsions. In both solutions, the permeate fluxes were enhanced by 80 % and 60 % under an ultrasonic field. In the resistance-in-series model, permeate flux decreases with an increase of the resistances caused by fouling phenomena (solute adsorption, etc.) and concentration polarization/gel layer formation. The correlation equations for estimating those resistances have been developed in this work. It was found that the resistances are functions of the applied pressure, volume ratio of W/O emulsions, operating power, and tip height. Finally, we made use of unstable of W/O emulsions at low pH, and demulsified at 63 watts of operating power under the ultrasonic field.

碩士
東南科技大學
防災科技研究所
101
Taiwan's EPA has conducted the effluent standard of ammonia. Therefore, ammonia removal from wastewater becomes an important issue recently. Traditional biological ammonia removal includs nitrification and denitrification, in addition,external organic carbon is needed. Therefore, increasing the cost of ammonia removal organic carbon is needed. There is a new ammonia removal technology called ANAMMOX process, which reduces the cost of ammonia removal. However, the ANAMMOX bacteria is difficult to cultivate and grows slowly. Therefore, avoid washing out of the ANAMMOX bacteria from the bioreactor is very important for actual application. This rearch combines the ANAMMOX process and membrane bioreactor technology to remove ammonia from wastewater. The research results indicate that membrane filtration avoided washing out of ANAMMOX bacteria, A serious experiments show that the ammonia loading,inorganic carbon addition. Magnesium addition and phosphorus addition has different effects on the ammonia removal rate of the bioreactor ln addition, Immobilization technology protected the ANAMMOX bacteria from Nitrite damage. The ammonia removal rate of the membrane bioreactor containing the suspended ANAMMOX bacteria is approximately 57.48 mg-N/day/g-MLSS, whereas, the rate is 20.33 mg-N/L/day for the bioreactor containing 15% immobilized ANAMMOX bacteria.

碩士
國立中央大學
光電科學研究所
95
The structure of traditional optical filter is mainly stacked by multi-thin-film, using the interfered phenomenon produced by the structure of stacked thin-film to get the effect of filtering light wave.Nevertheless, due to large size elements are frequently used in producing stacked thin-film structure, it is hard to combine with MEMS that is a tiny element by coating, to seriously allow for the factors such as refraction index, thickness, homogeneity and even stress between thin-film in each layer is necessary. In order to simplify the structure, this thesis represents Si-Based Free-Standing Guide-Mode Resonance Filter which total thickness is about 1 μm . Comparing with traditional optical filter stacked by multiple thin-film,when using Free-Standing Guide-Mode Resonance Filter, its structure become more uncomplicated and producing progress get more handy.Moreover, structure parameter can be exactly controlled as well.On design of Free-Standing Guide-Mode-Resonance Filter in this thesis, Q factor of structural spectrum can be promoted about 50% by adding low cladding layer. This thesis experimented to prove iv practicability of the design. Besides, this thesis controls the thickness of lower cladding layer to raise the transmission efficiency of sideband and make transmission efficiency more than 90% when wavelength is from 1.2 - 2.0 μ m . Differing from traditional Guide-Mode Resonance Filter, the sideband of high transmission efficiency can be increased around 400 nm with promoting the filter efficiency in a broadband. A Suspended-Membrane Type Guide-Mode Resonance Filter with lower cladding layer can be realized to substitute the traditional filter by our design, analysis, fabrication and measurement results. In addition, the practicability of Free-Standing Guide-Mode-Resonance Filter can be generally applied and its value and competitiveness will increase in market application.

Pattern formation in buckled membranes was studied along with the morphology of flowers formed at the tip of silicon nanowires and ripples formed in suspended graphene sheets. Nash's perturbation method was tested for a simple case where initial and final metrics embed smoothly and there is a smooth path from one surface to another and was found to work successfully. The method was tested in more realistic conditions where a smooth path was not known and the method failed. Cylindrical flower-like membranes with a metric of negative Gaussian curvature were simulated in three and four dimensions. These four dimensional flowers had 2 orders of magnitude less energy than their three dimensional counterparts. Simulations were used to show that the addition of a fourth spatial dimension did not relieve all bending energy from the cylindrical membranes. Patterns formed at the tip of silicon nanowires were studied and found to be of the Dense Branching Morphology type. The rate of branching is dependent on the curvature of the gold bubble on which they are grown. Graphene was simulated using the modified embedded atom method potential and buckles were found to form if the carbon bonds were stretched. An energy functional was found for the energy of a sheet with a metric different from that of flat space.
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