The application of adaptive micro-electro-mechanical systems (MEMS) device in biologically-inspired cochlear model (cochlear biomodel) has been seen as a preferable approach to mimic closely the human cochlear response. The thesis focuses on the design and fabrication of resonant gate transistor (RGT) device applied towards the development of RGT cochlear biomodel. An array of RGT devices can mimic the cochlea by filtering the sound input signals into multiple electrical outputs. The RGT device consists of two main components; a) the MEMS bridge gate structure that transduces the sound input into mechanical vibrations and b) the channel with source/drain regions underneath the bridge gate structure that transduce the mechanical vibrations into electrical signals. The created mathematical model for RGT calculates the electrical outputs that are suited for neural spike coding. The neuromorphic auditory system is proposed by integrating the RGT devices with the spike event interface circuits. The novelty of the system lies in the adaptive characteristics of the RGT devices that can self-tune the frequency and sensitivity using the feedback control signals from the neuromorphic circuits. The bridge gates have been designed to cover the audible frequency range signals of 20 Hz - 20 kHz. Aluminium and tantalum have been studied as the material for the bridge gate structure. The fabrication of a bridge gate requires a gentle etch release technique to release the structure from a sacrificial layer. The downstream etch release technique employing oxygen/nitrogen plasma has been introduced and characterised. In the first iteration, aluminium bridge gates have been fabricated. The presence of tensile stress within aluminium had caused the aluminium bridge gates of length >1mm to collapse. In order to address this issue, tantalum bridge gates have been fabricated in the second iteration. Straight tantalum bridge gates in tensile stress and buckled tantalum bridge gates in compressive stress have been characterised. The frequency range of 550 Hz - 29.4 kHz has been achieved from the fabricated tantalum bridge gates of length 0.57mm - 5.8mm. The channel and source/drain regions have been fabricated and integrated with the aluminium or tantalum bridge gate structures to create the RGTs. In this study, the n-channel and p-channel resonant gate transistor (n-RGT and p-RGT) have been considered. In n-RGT, phosphorus ions are implanted to form the source/drain regions. High subthreshold currents have been measured from the n-RGTs. Thus, p- RGTs have been employed with considerably small subthreshold current. In p-RGT, boron ions are implanted to form the source/drain regions. The threshold voltage, transconductance and subthreshold current for both n-channel and p-channel resonant gate transistor devices have been characterised. In this work, the channel conductance of the n-RGT and p-RGT devices has been modulated successfully and the sensitivity tuning within the audible frequency range has been achieved from the tantalum bridge gates of the p-RGT devices. The characterisation and optimisation of the resonant gate transistor provide the first step towards the development of the adaptive RGT cochlear biomodel for the neuromorphic auditory system application.

Micromachined accelerometers have found large attention in recent years due to their low-cost and small size. There are extensive studies with different approaches to implement accelerometers with increased performance for a number of military and industrial applications, such as guidance control of missiles, active suspension control in automobiles, and various consumer electronics devices. This thesis reports the development of various capacitive micromachined accelerometers and various integrated CMOS readout circuits that can be hybrid-connected to accelerometers to implement low-cost accelerometer systems. Various micromachined accelerometer prototypes are designed and optimized with the finite element (FEM) simulation program, COVENTORWARE, considering a simple 3-mask surface micromachining process, where electroplated nickel is used as the structural layer. There are 8 different accelerometer prototypes with a total of 65 different structures that are fabricated and tested. These accelerometer structures occupy areas ranging from 0.2 mm2 to 0.9 mm2 and provide sensitivities in the range of 1-69 fF/g. Various capacitive readout circuits for micromachined accelerometers are designed and fabricated using the AMS 0.8 &micro / m n-well CMOS process, including a single-ended and a fully-differential switched-capacitor readout circuits that can operate in both open-loop and close-loop. Using the same process, a buffer circuit with 2.26fF input capacitance is also implemented to be used with micromachined gyroscopes. A single-ended readout circuit is hybrid connected to a fabricated accelerometer to implement an open-loop accelerometer system, which occupies an area less than 1 cm2 and weighs less than 5 gr. The system operation is verified with various tests, which show that the system has a voltage sensitivity of 15.7 mV/g, a nonlinearity of 0.29 %, a noise floor of 487 Hz &micro / g , and a bias instability of 13.9 mg, while dissipating less than 20 mW power from a 5 V supply. The system presented in this research is the first accelerometer system developed in Turkey, and this research is a part of the study to implement a national inertial measurement unit composed of low-cost micromachined accelerometers and gyroscopes.

The field of microfluidics has the potential to provide a number of products to better everyday life, but is still not well understood. In previous research performed in the field, microfluidics has been shown to exhibit behavior different from what would be expected through normal pipe flow theory. While some research has shown that fluid flow through microchannels does conform to the theoretical flow mechanics, and thus can be predicted and understood through use of well-known relations; other research performed has indicated that fluid flow through microchannels experiences higher or lower pressure losses than would be expected with macro scale theory. This work strives to further explore and explain this anomaly by focusing on simple straight rectangular channels of varying hydraulic diameters from 24 µm to 88 µm, in order to form a more basic understanding for fluid flow in microchannels. Water was pumped through each of these channels at a number of different flow rates, and the static pressure was measured in two locations, a set length apart. The measured pressure loss over this length for each flow rate was then recorded and analyzed to provide relations between pressure loss and hydraulic diameter. Through the data obtained in this study, microfluidic flow of Reynolds numbers greater than 40 and in channels as small as 48 µm in diameter experienced pressure losses predicted from macroscale theory. Below these values, the data was more random, but still showed some conformance to theory. A clear relationship between measured pressure loss and hydraulic diameters over the entire range of channels was also found for two different flow rates. It is hoped that the data obtained will provide a better understanding of microfluidics and pave the way for potential applications to be realized.

In this work, we studied the electronic behavior of polymer-derived ceramics (PDCs) and applied them for the synthesis of carbon nanotube reinforced ceramic nanocomposites and ceramic MEMS (Micro-Electro-Mechanical Systems) structures. Polymer-derived SiCN ceramics were synthesized by pyrolysis of a liquid polyureasilazane with dicumyl peroxide as thermal initiator. The structural evolution during pyrolysis and post-annealing was studied using FTIR, solid state NMR and Raman. The results revealed that the resultant ceramics consisted of SiCxNx-4 as major building units. These units were connected with each other through C-C/C=C bonds or by shearing N/C. The amount of sp2 free carbon strongly depends on composition and processing condition. Electron paramagnetic resonance (EPR) was used to investigate electronic structure of PDCs; the results revealed that the materials contain unpaired electron centers associated with carbons. Electronic behavior of the SiCN ceramics was studied by measuring their I-V curves, temperature dependence of d.c.-conductivities and impendence. The results revealed that the SiCN ceramics exhibited typical amorphous semiconductor behavior, and their conductivity varied in a large range. The results also revealed that the materials contain more than one phase, which have the different electronic behavior. We explored possibility of using polymer-derived ceramics to make ceramic MEMS for harsh environmental applications with a lithography technique. The cure depth of the polymer precursor was measured as a function of UV intensity and exposure time. The experimental data was compared with the available theoretical model. A few typical SiCN parts were fabricated by lithography technique. We also prepared carbon nanotube reinforced ceramic nanocomposites by using PDC processing. The microstructures of the composites were characterized using SEM and TEM; the mechanical properties were studied characterized using nanoindentation. The significant improvement in mechanical properties was observed for the nanocomposites.

This thesis presents the optimization of deep reactive ion etching process (DRIE) to achieve high precision 3-dimensional integrated micro electro mechanical systems (MEMS) sensors with high aspect ratio structures. Two optimization processes have been performed to achieve 20 &amp / #956 / m depth for 1 &amp / #956 / m opening for a dissolved wafer process (DWP) and to achieve 100 &amp / #956 / m depth for 1 &amp / #956 / m opening for silicon-on-glass (SOG) process. A number of parameters affecting the etch rate and profile angle are investigated, including the step times, etch step pressure, platen power, and electrode temperature. Silicon etch samples are prepared and processed in METU-MET facilities to understand and optimize the DRIE process parameters that can be used for the production of MEMS gyroscopes and accelerometers. The etch samples for DWP are masked using a photoresist, Shipley S1813. After the optimization process, vertical trench profiles are achieved with minimum critical dimension loss for trench depths up to 20 &amp / #956 / m. Since the selectivity of the resist is not sufficient for 100 &amp / #956 / m deep trench etch process, silicon dioxide (SiO2) is used as the mask for this process. At the end of the optimization processes, more than 100 &amp / #956 / m depth for 1 &amp / #956 / m opening with almost vertical sidewalls are achieved. In summary, this study provides an extensive understanding of the DRIE process for successful implementations of integrated MEMS sensors.

This thesis reports the development of micromachined accelerometers and gyroscopes that can be used for micromachined inertial measurement units (IMUs). Micromachined IMUs started to appear in the market in the past decade as low cost, moderate performance alternative in many inertial applications including military, industrial, medical, and consumer applications. In the framework of this thesis, a number of accelerometers and gyroscopes have been developed in three different fabrication processes, and the operation of these fabricated devices is verified with extensive tests. In addition, the fabricated accelerometers were combined with external readout electronics to obtain hybrid accelerometer systems, which were tested in industrial test facilities. The accelerometers and gyroscopes are designed and optimized using the MATLAB analytical simulator and COVENTORWARE finite element simulation tool. First set of devices is fabricated using a commercial foundry process called SOIMUMPs, while the second set of devices is fabricated using the electroplating processes developed at METU-MET facilities. The third set of devices is designed for a new advanced process based on DRIE, which is under development. Mechanical and electrical test results of the fabricated accelerometers and gyroscopes are in close agreement with the designed values. The testing of the SOI and nickel accelerometers is also performed in industrial test environments. In order to perform these tests, accelerometers are hybrid connected to commercially available capacitive readout circuits. These accelerometer systems require only two DC supply voltages for operation and provide an analog output voltage related to the input acceleration. The industrial tests show that the SOI accelerometer system yields a 799 &micro / g/&amp / #8730 / Hz average noise floor, a 1.8 mg/&amp / #8730 / Hz peak noise floor, a 22.2 mV/g sensitivity, and a 0.1 % nonlinearity, while the nickel accelerometer system yields a 228 &micro / g/&amp / #8730 / Hz average noise floor, a 375 &micro / g/&amp / #8730 / Hz peak noise floor, a 1.02 V/g sensitivity, and a 0.23 % nonlinearity. Long-term drift components of the accelerometers are determined to be smaller than 20 mg. These systems are the highest performance micromachined accelerometer systems developed in Turkey, and they can be used in implementation of a national inertial measurement unit.

Στις τελευταίες δεκαετίες η σμίκρυνση (miniaturization) έχει αποτελέσει ένα σημαντικό παράγοντα στην ανάπτυξη της τεχνολογίας. Ένας από τους κύριους στόχους της μέσω της μικρομηχανικής (micro-engineering) είναι η παραγωγή ολοκληρωμένων Μικρο-Ηλεκτρο-Μηχανικών Συστημάτων (MEMS), τα οποία χρηςιμοποιούνται σήμερα ως υποσυστήματα σε πάρα πολλές εφαρμογές. Αντικείμενο της παρούσας διατριβής είναι ο παράλληλος χειρισμός καθώς και η ανοιχτού βρόχου/άνευ αισθητήρων συναρμολόγηση μικροαντικειμένων χωρίς τη χρήση μικροβραχιόνων. Για το σκοπό αυτό η έρευνα επικεντρώθηκε σε τέσσερις διαφορετικές διαδικασίες/προσεγγίσεις: α) το μικροχειρισμό με τρισδιάστατα πεδία δυνάμεων, β) το μικροχειρισμό με προγραμματιζόμενα πεδία δυνάμεων στο επίπεδο, γ) το χειρισμό μικροαντικειμένων έγκλειστων σε σταγόνες υγρού και δ) την αυτοσυναρμολόγηση μικροαντικειμένων με ηλεκτροστατικές δυνάμεις. / In the last decades, miniaturization has become an important factor in the development of technology. One of its main objectives through the discipline of micro-engineering is the production of integrated Micro-Electro-Mechanical Systems (MEMS), which are currently used as sub-systems in many applications. The target of this thesis is the parallel manipulation and the open-loop/sensorless assembly of microparts without the use of microrobots. For this purpose, the research was focused on four different procedures: a) micromanipulation with 3D force fields, b) micromanipulation with programmable force fields on a plane, c) manipulation of microparts enclosed in a droplet of liquid and d)self-assembly of microparts with electrostatic forces.

abstract: A Microbial fuel cell (MFC) is a bio-inspired carbon-neutral, renewable electrochemical converter to extract electricity from catabolic reaction of micro-organisms. It is a promising technology capable of directly converting the abundant biomass on the planet into electricity and potentially alleviate the emerging global warming and energy crisis. The current and power density of MFCs are low compared with conventional energy conversion techniques. Since its debut in 2002, many studies have been performed by adopting a variety of new configurations and structures to improve the power density. The reported maximum areal and volumetric power densities range from 19 mW/m2 to 1.57 W/m2 and from 6.3 W/m3 to 392 W/m3, respectively, which are still low compared with conventional energy conversion techniques. In this dissertation, the impact of scaling effect on the performance of MFCs are investigated, and it is found that by scaling down the characteristic length of MFCs, the surface area to volume ratio increases and the current and power density improves. As a result, a miniaturized MFC fabricated by Micro-Electro-Mechanical System(MEMS) technology with gold anode is presented in this dissertation, which demonstrate a high power density of 3300 W/m3. The performance of the MEMS MFC is further improved by adopting anodes with higher surface area to volume ratio, such as carbon nanotube (CNT) and graphene based anodes, and the maximum power density is further improved to a record high power density of 11220 W/m3. A novel supercapacitor by regulating the respiration of the bacteria is also presented, and a high power density of 531.2 A/m2 (1,060,000 A/m3) and 197.5 W/m2 (395,000 W/m3), respectively, are marked, which are one to two orders of magnitude higher than any previously reported microbial electrochemical techniques. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2016

Accelerometer sensors fabricated with micromachining technologies started to take place of yesterday&rsquo / s bulky sensors in many application areas. The application areas include a wide range from consumer electronics and health systems to military and aerospace applications. Therefore, the performance requirements extend form 1 &mu / g&rsquo / s to 100 thousand g&rsquo / s. However, high performance strategic grade MEMS accelerometer sensors still do not exist in the literature. Smart designs utilizing the MEMS technology is necessary in order to acquire high performance specifications. This thesis reports a high performance accelerometer with a new process by making the use of bulk micromachining technology. The new process includes the utilization of Silicon-on-Insulator (SOI) wafer and its buried oxide (BOX) layer. The BOX layer helps to realize interdigitated finger structures, which commonly find place in surface micromachined CMOS-MEMS capacitive accelerometers. The multi-metal layered CMOS-MEMS devices inherently incorporate interdigitated finger structures. Interdigitated finger structures are highly sensitive to acceleration in comparison with comb-finger structures, which generally find usage in bulk-micromachined devices, due to absence of anti-gap. The designed sensors based on this fabrication process is sought to form a fully-differential signal interfaced sensor with incorporation of the advantages of high sensitive interdigitated finger electrodes and high aspect ratio SOI wafer&rsquo / s bulk single crystal silicon device. Under the light of the envisaged process, sensor designs were made, and verified using a computing environment, MATLAB, and a finite element analysis simulator, CoventorWARE. The verified two designs were fabricated, and all the tests, except the centrifuge test, were made at METU-MEMS Research Center. Among the fabricated sensors, the one designed for the high performance achieves a capacitance sensitivity of 178 fF with a rest capacitance of 8.1 pF by employing interdigitated finger electrodes, while its comb-finger implementation can only achieve a capacitance sensitivity of 75 fF with a rest capacitance of 10 pF.

Orientador: Luiz Otavio Saraiva Ferreira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-06T16:27:32Z (GMT). No. of bitstreams: 1 Espindola_AlexeyMarques_M.pdf: 1293939 bytes, checksum: 66ab2d16dc552294762d6c3708cda71b (MD5) Previous issue date: 2006 / Resumo: Os sistemas microfluidicos estão evoluindo rapidamente, encontrando vastas aplicações na mais diversas áreas do conhecimento. Os Lab-on-Chips, LOCs, são dispositivos capazes de realizar análises químicas e bioquímicas em um único chip. Este dispositivo pode causar grande impacto no mercado de análises laboratoriais, por este motivo vem ganhando grande atenção Para realizar estas análises os LOCs necessitam de microbombas capazes de transportar quantidades ínfimas de fluidos em seus canais de maneira acurada e uniforme. Desta forma, o interesse em modelar e fabricar microbombas tomou-se uma área fértil para a pesquisa. Neste trabalho foi desenvolvida a modelagem de uma microbomba peristáltica de elastõmero, tipo de bomba mais conveniente para Lab-on-Chips, utilizando a técnica de analogias eletro-mecânicas que consiste em representar um dispositivo por um circuito elétrico equivalente. As análises das simulações podem ser realizadas usando programas de análise de circuitos elétricos. Dois modelos foram apresentados neste trabalho. O primeiro é a reprodução do modelo de bomba criado por Jacques Goulpeau, em que o modelo de uma válvula é extrapolando para toda a microbomba. O segundo contém o circuito elétrico equivalente da bomba completa mostrando a interações entre suas partes. Os resultados mostram que o comportamento da microbomba não pode ser completamente descrito pelo modelo extrapolado a partir de uma válvula, devido às interações entre três válvulas. As simulações do circuito equivalente da bomba completa mostraram que os efeitos das interações entre as válvulas explicam claramente a diferença entre a vazão prevista pelo modelo de Goulpeau e os dados experimentais por ele obtidos, sendo possível ajustar o modelo aos dados experimentais / Abstract: Microfluidies systems are growing rapidly, finding a large nwnber of applications in many fields. Lab-on-ehips, LOC, are deviees that ean perform ehemical and biochemical analyses in a ehip. This device ean cause high impact on laboratorial analyses market, and then it is gaining large attention. In order to execute these analyses on LOC, mieropumps are necessary to transport a tiny quantity of fluid between the channeIs with accuracy and uniformity. Thus, the interests of modeling and fabrication mieropwnps are increasing and become a fertile research field. The goal of this work were a modeling of elastomer peristaltic micropwnp, the most suitable pwnp for LOCs, using the electro- mechanical analogy technique that consist in represent the device in a electrical equivalent networks. Then the simulation analyses can be done on electrical simulation tools. Two models were presented in this work. The first is reproduction of the pwnp model made by Jacques Goulpeau et aI., where the valve model is extrapolated to the whole mieropwnp. The second contains the electrical equivalent circuit that represents the whole device showing the interactions between its eomponents. The results showed that micropump behavior eouldn't completely deseribe by the extrapolated model ftom a valve, because the interactions between the three valves. The simulations of electrical equivalent eircuit of the whole pwnp showed that the interaction between the valves explain the difference between of flow rate foreseen by Goulpeau model and his experimental data, being possible to adjust the model to the experimental data / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica