Browsing by Subject "MEMS"
Now showing 1 - 18 of 18
- Results Per Page
- Sort Options
Item A bidirectional MEMS thermal actuator as the building block for a programmable metamaterial(2018-10-04) Zhao, Cheng, M.S. in Engineering; Cullinan, MichaelThis thesis presents a novel bidirectional MEMS thermal actuator that is intended to be implemented as the building block for a microarchitectured material. The successful proof of concept demonstrates the potential for a new level of miniaturization for the technology that would improve existing capabilities and enable new ones. The design is built upon the bent-beam type thermal actuators with an emphasis on large travel and force output. Sensing capabilities are accomplished through piezoresistive strain gauges that provide sufficient sensitivity and resolution. An analytical model was created to calculate the performance parameters of actuator designs and was used in conjunction with optimization software to arrive at four selected designs with minimal theoretical trade-offs. Successful fabrication of the devices was achieved with standard microfabrication techniques. Preliminary testing results have demonstrated the successful operation of bidirectional actuation and confirms the validity of the conceptItem A MEMS dynamic mechanical analyzer for in situ viscoelastic characterization of 3D printed nanostructures(2020-05-11) Cayll, David Richard; Cullinan, MichaelCellular, metamaterial structures with sub-micron features have shown the ability to become excellent energy absorbing materials for impact mitigation due to the enhanced mechanical properties of materials at the nanoscale. However, in order to optimize the design of these energy absorbing metamaterial structures we need to be able to measure the dynamic properties of the sub-micron features such as storage and loss moduli and the loss factor. Therefore, at-scale testing is required to capture the scale, temperature, and strain rate dependent material properties of these nanoscale materials. This thesis presents the design, fabrication, and calibration of a MEMS-based dynamic mechanical analyzer (DMA) that can be directly integrated with the two-photon lithography (TPL) process commonly used to fabricate metamaterial structures with nanoscale features. The MEMS-based DMA consists of a chevron style thermal actuator used to generate a tensile load on the structure and two differential capacitive sensors on each side of the structure used to measure load and displacement. This design demonstrated 1.5 ± 0.75 nm displacement resolution and 104 ± 52 nN load resolution, respectively. Dynamic mechanical analysis was successfully conducted on a single nanowire feature printed between the load and displacement stages of the MEMS device with testing frequencies ranging between 0.01 – 10 Hz and testing temperatures ranging between 22°C - 47°C. These initial tests on an exemplar TPL part demonstrate that the printed nanowire behaves as a viscoelastic material wherein the transition from glassy to viscous behavior has already set in at the room temperature.Item A novel fabrication process for CMUTs in air(2017-12) Hord, Samuel Kay; Hall, Neal A.; Wilson, Preston SA novel fabrication method for producing capacitive micromachined ultrasonic transducers (CMUTs) is presented. The process uses conductive silicon on insulator (SOI) substrates to produce an unstressed transducer diaphragm. By etching release holes through the device layer and selectively removing the underlying buffered oxide (BOX) layer, an ultrasonic transducer can be made using only two photolithography steps. The process is described in detail, including models predicting the modal behavior and the collapse voltage of the device. The acoustical behavior of a perforated plate over a sealed cavity is modeled using mechano-acoustical circuit analysis. The device is found to produce sound despite the perforations so long as the holes are sufficiently small and the frequency of operation is sufficiently high. A pitch-catch measurement verifies the transduction of the device. To the author’s knowledge, this is the simplest method for CMUT fabrication to date.Item Design and analysis of a new sensing technique for casing joint validation through integrating turns measurement into a torque sensor(2012-12) Hall, Russell Ilus; Chen, Dongmei, Ph. D.Fossil fuels and their byproducts are a vital part of our economy, and society. Until renewable energy sources and energy storage technologies advance to the point where they are reliable and inexpensive, the US Economy will continue to depend upon fossil fuels. Current resources are being consumed, and the "easy to reach" reserves are becoming depleted. This leads to the requirement for more exploratory drilling, and the potential for more disasters like the recent Deepwater Horizon spill in the Gulf of Mexico. Drilling is the first of several steps in the creation of a productive oil or natural gas well. Completing a well involves casing the walls in concrete to prevent damage to the surrounding rock formations and to ensure that all of the oil or gas is captured without escaping to the surrounding environment. Ensuring the piping, which is used to case wells, is assembled correctly and to manufacturer's specifications is the focus of this study. Individual pipe sections are screwed together with a requirement for torque and number of turns. Each joint must be verified to ensure integrity, and minimize the possibility of a spill or leak. The torque measurement can be accomplished by a "torque sub", a sensor installed in-line with the drill string. The torque sub is a wireless sensor that transmits torque data to the control system for logging and display. This thesis defines the parameters required to integrate a "number of turns" measurement into an existing torque sub so that both parameters can be captured, recorded and reported using a single device. The Yost Engineering 3-Space Sensor was evaluated for use in this application. The configuration that gave the most accurate data was selected, along with the determination of some correction factors to account for site specific variation in the signals. A calibration algorithm is discussed, along with several unique methods for ensuring that the sensor output doesn't drift over the course of the joint make-up process.Item Design of a MEMS-based tunable graphene resonator with precision strain and force metrology(2016-05) Sun, Guoao; Cullinan, Michael; Akinwande, DejiMade of only on sheet of carbon atoms, graphene is the thinnest yet strongest material ever exist. Since its discovery in 2004, graphene have attracted tremendous research effort worldwide. Guaranteed by the superior electrical and excellent mechanical properties, graphene is the ideal building block for Nanoelectromechanical System (NEMS). However, one of the major challenges in producing highly accurate graphene-based nanoelectromechanical (NEMS) resonators is the poor fabrication repeatability of graphene-based NEMS devices due to small variations in the residual stress and initial tension of the graphene film. This has meant that graphene-based nanoelectromechanical resonators tend to have large variations in natural frequency and quality factor from device to device. However, by actively controlling the tension on the graphene resonator it is possible both to increase repeatability between devices and to increase the force/mass sensitivity of the nanoelectromechanical resonators produced. Such tension control makes it possible to produce electrometrical filters that can be precisely tuned over a frequency range of up to several orders-of-magnitude. In order to controllably strain the graphene resonator, a microelectromechanical system (MEMS) is designed and used to apply tension to the graphene. The MEMS device consists of a graphene resonator, electro-thermal actuator and two differential capacitive sensors. Using this setup, it is not only possible to tune the natural frequency of the graphene resonator, but also possible to perform high precision force and strain metrology on graphene beam. In addition to designing devices that can compensate for manufacturing errors in nanomanufactured devices, this thesis will present several methods that can greatly expand the scope and rate at which nanomaterials-based devices can be fabricated.Item Design of Acoustic MEMS Metamaterials with Programmable Nonreciprocity(2022) Nguyen, Daniel; Cullinan, MichaelAn increasing number of non-reciprocal acoustic devices have been developed in recent years as potential methods of solving problems in wave-guiding, vibration isolation, and energy harvesting. Yet to date, non-reciprocal acoustic behavior has not been demonstrated at a micro-scale and has largely been limited to frequency regions close to existing resonances or band gaps. In this paper, we present the design of MEMS metamaterial capable of demonstrating non-reciprocal acoustic behavior, which could potentially contribute to new applications at the micro-scale. Several chip designs are presented that contain longitudinal chains of symmetric parallel-plate unit cells that possess open loop controllable stiffness, designed in line with SOIMUMPs and POLYMUMPs fabrication standards. The device designs demonstrate that electronically controlled unidirectional bandgaps are achievable at the micro-scale with designs subject to traditional MEMS fabrication constraints.Item Design of an optical microelectromechanical-system microphone with sub 15-dBA noise floor(2018-05-02) Kim, Donghwan, 1981-; Hall, Neal A.; Hamilton, Mark F.; Ho, Paul S.; Wilson, Preston S.; Yu, Edward T.This research work presents the modeling, fabrication, and characterization of the optical microphone. The optical microphone detects diaphragm displacement due to input sound pressure, using an interferometric-based displacement detection scheme instead of using capacitive readout technique, which is extensively used in commercial microelectromechanical-system microphones. The optical-based transduction mechanism enables a backplate design with an extremely high perforation density, which in-turn drastically reduces the backplate flow resistance, which is a dominant noise source in miniaturized microphones. Therefore, an accurate estimation of the backplate-induced flow resistance is a critical step to predict signal-to-noise ratio precisely. A flow resistance modeling technique via computational fluid dynamics is presented in this work. A prototype backplate is fabricated for a verification of the flow-resistance modeling technique. A 22.0-dBA noise floor is demonstrated using the prototype backplate, which is 6-dB better than state-of-the-art commercial capacitive MEMS microphones. Design of experiments were performed with the verified microphone model to illustrate design implications toward sub 15-dBA optical microphone. The design-of-experiments study focused on various microphone components including diaphragm compliance, acoustical low cut-off frequency, back-cavity volume, inlet port and vent to show how each parameter affect to the microphone signal-to-noise ratio and acoustic overload point. Finally, a force-feedback optical microphone concept is presented to achieve a higher acoustic overload pressure, which is defined by 10% total harmonic distortion, using a Si membrane with piezoelectric thin-film actuators. A feasibility study was performed to explore the concept of a force-feedback optical microphone, including a fabrication of the minimalistic backplate with high aspect-ratio spokes and Si membrane with piezoelectric-film actuators at Microelectronics Research Center at The University of Texas at Austin.Item Design, fabrication, and evaluation of a biologically-inspired piezoelectric MEMS microphone with in-plane directivity(2019-12) Stalder, Carly Amanda; Hall, Neal A.This work examines the directional hearing capabilities of the fly Ormia ochracea and how they are applied to microelectronics. The fly can auditorily determine the direction of a cricket chirp, though the wavelength of the chirp is more than ten times longer than the length of the fly's hearing mechanism. The design, modeling, fabrication, and evaluation of a microphone that harnesses this fly's hearing ability are explored. The device consists of a two-sided cantilever beam that rotates about torsional pivots located along the y-axis. The result is two main frequency modes that can be used in the sound localization process for in-plane directivity in the x-direction: a gradient mode that causes opposite ends of the beam to move out-of-phase, and a symmetrical mode that causes the ends of the beam to move in-phase. Springs connect the free ends of the beam to the center pivot. Strain in these springs is converted to a voltage at the output. The microphones are fabricated on a silicon-on-insulator wafer with a 2 μm-thick device layer and 500 nm-thick aluminum nitride film as the piezoelectric transduction material. The active beam measures 500 x 250 μm², which approaches the dimensions of the fly's ear and is the smallest version of the microphone to date. The sensing modes are modeled with finite element analysis and confirmed in multipoint scans. Preliminary directivity measurements are made to demonstrate the directional capabilitiesItem Design, fabrication, and testing of a MEMS z-axis Directional Piezoelectric Microphone(2012-05) Kirk, Karen Denise; Hall, Neal A.; Neikirk, Dean P.Directional microphones, which suppress noise coming from unwanted directions while preserving sound signals arriving from a desired direction, are essential to hearing aid technology. The device presented in this paper abandons the principles of standard pressure sensor microphones, dual port microphones, and multi-chip array systems and instead employs a new method of operation. The proposed device uses a lightweight silicon micromachined structure that becomes “entrained” in the oscillatory motion of air vibrations, and thus maintains the vector component of the air velocity. The mechanical structures are made as compliant as possible so that the motion of the diaphragm directly replicates the motion of the sound wave as it travels through air. The microphone discussed in this paper achieves the bi-directionality seen in a ribbon microphone but is built using standard semiconductor fabrication techniques and utilizes piezoelectric readout of a circular diaphragm suspended on compliant silicon springs. Finite element analysis and lumped element modeling have been performed to aid in structural design and device verification. The proposed microphone was successfully fabricated in a cleanroom facility at The University of Texas at Austin. Testing procedures verified that the resonant frequency of the microphone, as expected, was much lower than in traditional microphones. This report discusses the theory, modeling, fabrication and testing of the microphone.Item Fabrication and Control of a Microheater Array for Microheater Array Powder Sintering(University of Texas at Austin, 2017) Holt, Nicholas; Galvan Marques, Lucas; Van Horn, Austin; Montazeri, Mahsa; Zhou, WenchaoMicroheater Array Powder Sintering (MAPS) is a novel additive manufacturing process that uses a microheater array to replace the laser of selective laser sintering as the energy source. Most of the previous research on microheaters are for applications in gas sensing or inkjet printing. The operation temperature and response time of the microheater array are critical for the choice of sintering materials and printing speed for the MAPS process. In this paper, we present the fabrication, packaging, and control of a platinum microheater array that has a target operation temperature of 400°C and a response time of ~1 millisecond. First, we will present the fabrication process of a microheater array. The fabricated microheater array is then packaged for easy control and to serve as the printhead of the MAPS process. A PID controller is designed to control the temperature response of the microheater. Finally, the effectiveness of the controller is evaluated. Results show the fabricated microheater array satisfies the design requirements for the MAPS process.Item Innovative design, assembling and actuation of arrays of nanoelectromechanical system (NEMS) devices using nanoscale building blocks(2015-05) Kim, Kwanoh; Fan, Donglei; Bourell, David L; Chen, Ray; Manthiram, Arumugam; Mullins, Charles BuddieRotary nanomotors, a type of nanoelectromechanical system (NEMS) device that converts electric energy into mechanical motions, are critical for advancing NEMS technology in various fields but have been difficult to obtain using traditional techniques. As a consequence, it is highly desirable to investigate new mechanisms to develop large arrays of rotary NEMS devices with high efficiency, small size, and reliable performance at a low cost. In this dissertation, we report innovative designs and mechanisms for assembling and actuating arrays of rotary NEMS devices based on the electric tweezers and unique magnetic interactions among components. NEMS oscillators and motors were assembled from nanoscale building blocks including nanowires working as rotors, patterned nanomagnets as bearings, and quadrupole electrodes as stators. Multiple devices could be assembled in an ordered array and rotated either between two designated angles reciprocally or the full cycles continuously with controlled angle, speed (over 18,000 rpm) and chirality. Their fundamental electric, magnetic, and mechanical interactions were investigated, which provided an understanding of nanoscale dynamics critical to designing and actuating various metallic NEMS devices. We could reduce the size of the device with all its characteristic dimensions below 1 micron and continuously rotate a nanomotor for up to 15 hours, which is equivalent to more than 240,000 cycles in total. As an application, NEMS devices were used for controlled biochemical release and demonstrated the releasing rate of biochemical from the devices could be precisely tuned by mechanical rotation. Various magnetic configurations were purposely designed and successfully implemented, which resulted in distinct rotation behaviors including repeatable wobbling and self-rolling in addition to in-plane rotation. With the understandings of these rotation characteristics, high-performance micromotors have been rationally designed and successfully achieved, where the micromotors rotate at uniform speeds and position at desired angles, resembling step motors. Bioinspired micromotors comprised of three-dimensional porous diatom frustule rotors and patterned micromagnets were assembled and rotated in a microfluidic channel. Simulation results showed that they could stir and agitate liquid in a microchannel more efficiently than simple one-dimensional nanoentities and would be promising for microfluidic actuators. The innovations reported here, including concept, design, fabrication, actuation mechanisms, and applications, are expected to inspire various research areas including NEMS, nanorobotics, biomedical applications, microfluidics and lab-on-a-chip architectures.Item Measurement of the effect of growth quality and number of layers on the mechanical properties of graphene using a MEMS tensile tester(2022-08-30) Cho, Joon Hyong; Cullinan, MichaelMain goal of research is to measure mechanical properties of graphene grown under different conditions mainly controlling growth substrate and growth pressure of the graphene to control the number of graphene layers grown. Mechanical properties of graphene are measured in many ways, yet conventional mechanical tensile testing of graphene sheets is difficult due to one atomic thickness of graphene and difficulties in handling graphene tensile specimen in nanoscale. I propose to implement Microelectromechanical System (MEMS) based tensile tester to accurately measure the mechanical properties of suspended graphene from strain versus stress curve. Understanding mechanical properties of graphene in nanoscale can be beneficial in many application perspectives. First, mechanically tested graphene on MEMS device can be used as a graphene-based nanoscale device such as precision displacement sensors, load detectors, and electrical filters. One of the major challenges in producing highly accurate graphene-based nanoscale devices is the poor fabrication repeatability of graphene-based nanoscale devices due to small variations in the residual stress and initial tension of the graphene film. This has meant that graphene-based nanoscale devices tend to have large variations in natural frequency and quality factor from device to device. This poor repeatability makes it impossible to use these devices to make accurate, high-precision force and displacement sensors or electromechanical filters. However, by actively controlling the tension on the graphene it is possible both to increase repeatability between devices and to increase the force/mass sensitivity of the nanoelectromechanical resonators produced. Second, in addition to designing devices that can compensate for manufacturing errors in nano-manufactured devices, several methods are proposed to greatly expand the scope and rate at which nanomaterials-based devices can be fabricated. For example, a transfer-free, wafer-scale manufacturing process can be used to produce suspended graphene-based devices such as the graphene-based nanoelectromechanical resonators in the wafer scale. Therefore, for the scope of the research, it is necessary to 1) understand the growth parameters of graphene on thin film which determines the overall quality of graphene, 2) find the methods to control the uniformity and thickness of graphene, 3) successfully implement and test graphene MEMS tensile tester, and 4) analyze and compare the tensile testing results of graphene to previously conducted research. As a result, ideal adhesion layer for platinum thin film and thickness for Cu-Ni composite alloy are investigated for growing defect less, uniform, continuous monolayer graphene. In addition, we have found a critical parameter which can control the number of graphene layers on Cu foil. We obtained graphene layers from mono to 15 layers by controlling only the growth pressure. We also have developed an effective and repeatable graphene transfer process which enables us to transfer small patterned graphene onto graphene MEMS devices. Lastly, we have tested mechanical properties of different number of graphene layers on MEMS tensile tester and obtained critical strain energy release rate of fracture as 145 J/m², 71.3 J/m², and 22 J/m² with ~15 layers, ~10 layers, and ~5 layers of graphene, respectively. Also, gauge factors were calculated according to ~15, ~10, and ~5 graphene layers to be 3.76, 3.09, 12.35, respectively. Detecting strain change in multilayer graphene layer above 5 layers by Raman spectroscopy was challenging since rate of Raman shift was as low as 0.05 cm⁻¹ per percentage of strain change compared to 0.328 cm⁻¹/%ε of monolayerItem Mechanical characterization of two-photon polymerization submicron features(2018-12) Ladner, Ian Seth; Cullinan, Michael; Saha, Sourabh K; Li, Wei; Liechti, Kenneth M; Seepersad, Carolyn CTwo-photon polymerization (TPP) is promising method for additively manufacturing nanoscale structures with complex geometries. For example, TPP has been used to fabricate very high strength-to-weight lattice structures that can be used in a variety of biomedical and aerospace applications. However, one of the major factors limiting TPP as a true manufacturing technique is the uncertainty in how printing parameters affect the mechanical properties of the materials produced at the voxel level. Therefore, the purpose of this thesis is to characterize the scale dependent effects of speed, power, and post curing methods on TPP resists. In order to achieve this purpose, a custom MEMS tensile tester was designed, fabricated, and calibrated for direct integration into the TPP process with resolution and range capable of measuring <200 nm wide voxel lines. Direct integration was accomplished by applying stiction constraints to the suspended elements and fabricating anti-stiction features under the device layer. The load and displacement stages were measured to have a 100 nN and 1.5 nm resolution, respectively, using digital image correlation. The MEMS tensile tester was used to determine the material properties of TPP voxels written at low and high speeds. High speed voxels were fabricated with line widths varying from 196 nm to 444 nm by increasing the laser power. Both speeds were post processed with three different curing methods. The improvement in elastic modulus from high speed to low speed writing was a determined to be factor of ~2.1. However, it was also found that a UV post cure with radical generators could be used to produce matching material properties between the two writing speeds. That trend is critical for being able to increase the throughput of TPP without scarifying the performance of the fabricated materials. Finally, a strong size effect was found in these TPP materials with a non-linear increase in the elastic modulus (from 3.92 – 6.54 GPa) occurring when the TPP line width was decreased from 444 nm to 196 nm for the UV with radicals post cure conditionItem Methods to achieve wavelength selectivity in infrared microbolometers and reduced thermal mass microbolometers(2010-12) Jung, Joo-Yun, 1976-; Neikirk, Dean P., 1957-; Bank, Seth; Belkin, Mikhail; Hall, Neal; Rogers, Robert L.The use of a patterned resistive sheet as an infrared-selective absorber, including the effects of a mechanical support dielectric layer is discussed. Also, modified dielectric coated Salisbury Screen can improve both the wavelength selectivity and the speed of thermal response for microbolometers. These patterned resistive sheets and Modified dielectric coated Salisbury Screen are a modified form of classical Salisbury Screens that utilize a resistive absorber layer placed a quarter-wavelength in front of a mirror. These structures can show a narrower detection bandwidth when compared to conventional microbolometers. For a Modified dielectric coated Salisbury Screen for multi-spectral system, wavelength selectivity can be varied by changing the distance to the mirror, and for patterned resistive sheet, wavelength selectivity can be varied by changing the lithographically drawn parameters of the array. Hence, different pixels in a focal plane array can be designed to produce a “multi-color” infrared imaging system. Also, the thermal mass of microbolometer is reduced using patterned resistive structure.Item Microheater Array Powder Sintering: A Novel Additive Manufacturing Process(University of Texas at Austin, 2017) Holt, Nicholas; VanHorn, Austin; Montazeri, Masha; Zhou, WenchaoOne of the most versatile additive manufacturing (AM) processes is selective laser sintering (SLS), which scans a powder bed with a laser beam to fuse powder particles layer by layer to build 3D objects for prototypes and end products with a wide range of materials. However, it suffers from slow printing speed due to the pointwise scanning and high energy consumption due to the requirement of a high-power laser. In this paper, we propose a novel method of additive manufacturing which replaces the laser beam with an array of microheaters as an energy source to sinter powder particles. This method, referred to as Microheater Array Powder Sintering (MAPS), has the potential to significantly increase the printing speed by layer-wise sintering and reduce the power consumption due to the lower power requirements of the microheater array. This paper is to provide a proof-of-concept for this proposed new method. First, a thin-film microheater is designed and simulated with an experimentally validated numerical model to demonstrate that it can be used as an alternative energy source to sinter powder particles by reaching a target temperature of 600°C within milliseconds at a power consumption of 1.2 Watts. The numerical model is used to simulate the MAPS process by placing the heater in close proximity to the powder particles. Simulation results show that heat can be effectively transferred over an air gap to raise the temperature of the powder particles to their sintering temperature. Different process parameters (e.g., air gap, material properties, time, printing resolution, etc.) are discussed. An experimental MAPS system is then implemented to provide a proof-of-concept with the designed microheater and a custom air gap control apparatus. A straight line is successfully printed on thermal paper using the experimental MAPS system, which suggests the proposed MAPS process is feasible.Item Micromachined in-plane acoustic pressure gradient sensors(2014-05) Kuntzman, Michael Louis; Hall, Neal A.; Champlin, Craig A; Driga, Mircea D; Hamilton, Mark F; Neikirk, Dean PThis work presents the fabrication, modeling, and characterization of two first-generation acoustic in-plane pressure gradient sensors. The first is a micromachined piezoelectric microphone. The microphone structure consists of a semi-rigid beam structure that rotates about torsional pivots in response to in-plane pressure gradients across the length of the beam. The rotation of the beam structure is transduced by piezoelectric cantilevers, which deflect when the beam structure rotates. Sensors with both 10 and 20-μm-thick beam structures are presented. An analytical model and multi-mode, multi-port network model utilizing finite-element analysis for parameter extraction are presented and compared to acoustic sensitivity measurements. Directivity measurements are interpreted in terms of the multi-mode model. A noise model for the sensor and readout electronics is presented and compared to measurements. The second sensor is a capacitive sensor which is comprised of two vacuum-sealed, pistons coupled to each other by a pivoting beam. The use of a pivoting beam can, in principle, enable high rotational compliance to in-plane small-signal acoustic pressure gradients, while resisting piston collapse against large background atmospheric pressure. A design path towards vacuum-sealed, surface micromachined broadband microphones is a motivation to explore the sensor concept. Fabrication of surface micromachined prototypes is presented, followed by finite element modeling and experimental confirmation of successful vacuum-sealing. Dynamic frequency response measurements are obtained using broadband electrostatic actuation and confirm a first fundamental rocking mode near 250 kHz. Successful reception of airborne ultrasound in air at 130 kHz is also demonstrated, and followed by a discussion of design paths toward improve signal-to-noise ratio beyond that of the initial prototypes presented. A method of localizing sound sources is demonstrated using the piezoelectric sensor. The localization method utilizes the multiple-port nature of the sensor to simultaneously extract the pressure gradient and pressure magnitude components of the incoming acoustic signal. An algorithm for calculating the sound source location from the pressure gradient and pressure magnitude measurement is developed. The method is verified by acoustic measurements performed at 2 kHz.Item Modeling and prototyping of a micromachined optical microphone(2010-12) Kuntzman, Michael Louis; Hall, Neal A.; Wilson, Preston S.A microelectromechanical systems (MEMS) optical microphone that measures the interference of light resulting from its passage through a diffraction grating and reflection from a vibrating diaphragm (JASA, v. 122, no. 4, 2007) is described. In the present embodiment, both the diffractive optical element and the sensing diaphragm are micromachined on silicon. Additional system components include a semiconductor laser, photodiodes, and required readout electronics. Advantages of this optical detection technique have been demonstrated with both omni-directional microphones and biologically inspired directional microphones. In efforts to commercialize this technology for hearing-aids and other applications, a goal has been set to achieve a microphone contained in a small surface mount package (occupying 2mm x 2mm x 1mm volume), with ultra-low noise (20 dBA), and broad frequency response (20Hz–20kHz). Such a microphone would be consistent in size with the smallest MEMS microphones available today, but would have noise performance characteristic of professional-audio microphones significantly larger in size and more expensive to produce. This paper will present several unique challenges in our effort to develop the first surface mount packaged optical MEMS microphone. The package must accommodate both optical and acoustical design considerations. Dynamic models used for simulating frequency response and noise spectra of fully packaged microphones are presented and compared with measurements performed on prototypes.Item Optimization of in-plane directional microphone(2015-08) Zha, Jingqiang; Hall, Neal A.; Masada, GlennThis report is aimed at optimization of the in-plane directional microphone. In chapter 1, a piezoelectric network model is presented. Then the network model is applied to a piezoelectric cantilever beam. Theoretical results are compared with simulation results to prove the network model. This piezoelectric cantilever beam also forms the basis of the XY directional microphone. In chapter 2, principles of XY directional microphone are explained at the beginning. Further analysis shows the expression related to signal-to-noise ratio, which is the optimization goal. ANSYS simulation is implemented to justify this expression. Based on that expression, suggestions are made to optimize the directional microphone. In chapter 3, proof of concept of a novel gyroscope directional microphone is explained. Gyroscopic effect is introduced at first. Then the result of in-plane directional microphone is presented. Finally, the expression for "amplification factor" is derived and selection of appropriate performance criterion could lead to improved sensitivity.