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We report record-high performance from a fused-silica micro Precision Shell Integrating (PSI) gyroscope. The PSI gyroscope uses a fused-silica resonator with a diameter of 1 cm and a mechanical quality factor (Q) of 5.2 million. The gyroscope has an angle random walk (ARW) of 0.00016 deg/√hr and short-term in-run bias instability of 0.0014 deg/hr without any temperature compensation. This performance for such a small shell gyroscope compares well with the larger mHRG and HRG devices reported previously. This performance, in a device this small, is achieved by optimizing the fabrication of the shell resonator so it provides high Q, large mass, high frequency resonance, and low as-fabricated frequency mismatch.

A high Q-factor and mode-matched silicon MEMS gyroscope composed of a ladder structure has been developed. The ladder structure that is capable of suppressing energy dissipation has allowed the Q-factors of drive and sense modes to reach 120,000, which is a great value as a Si-tuning fork gyroscope. Moreover, the mode-matched high Q-factor ladder gyroscope shows an angle random walk (ARW) of 0.020 deg/√h and a bias instability (BI) of 0.20 deg/h. These measured results demonstrate that the ladder structure has enabled this silicon gyroscope to achieve high performance that is required for autonomous driving systems.

This paper reports measured results for a fused-silica precision shell integrating (PSI) micro gyroscope employing out-of-plane drive/sense transduction mechanism. The PSI gyroscope is made with a 5 mm radius shell resonator operating in $n=2$ wine-glass mode at a frequency ( $f_{n=2}$ ) of 5.803 kHz with as-fabricated frequency split ( $\Delta f$ ) of 2.1 Hz. Large and reasonably uniform capacitance (∼0.25 pF) is achieved with flat surface electrodes. The gyroscope is operated in the force-rebalance mode by interfacing with an ultra-low-noise transimpedance amplifier (TIA). Near-navigation grade angle random walk (ARW) of $0.0062\ \deg/\sqrt{\mathrm{h}}\mathrm{r}$ , in-run bias instability (BI) of 0.027 deg/hr and scale factor of 158 mV/deg/s without any temperature compensation are achieved.

Many wireless sensor networks benefit from one type of time synchronization protocols. However, due to different crystal oscillators and clock sources in the nodes, even with drift-management techniques, synchronization error starts increasing fast after a few to tens of seconds. To keep the error low in minute-long sessions, typically the master transmits packets periodically to reset the error. These extra packets increase power consumption of all nodes especially in long sessions. Here, we propose AdaptSync that uses the timing/error information of a short period of time at the beginning of a session to reduce the error in the rest of the session independent of the master. Implementation steps are discussed and tested on sensor nodes that use Bluetooth as the wireless link. Experimental results show that in 10-minute long sessions, average synchronization error is reduced 7x compared to normal synchronization.

This paper presents a modular and generic micromachined oven-control system for use with miniature micro-electro-mechanical system (MEMS) transducers. The micro-oven-controlled off-the-shelf commercial six-axis MEMS inertial measurement unit (IMU), Invensense MPU-6050, provides the lowest reported temperature-induced root of sum of squares bias errors of 62.71°/h and 1.920 mg from -40°C to 85°C for three-axis gyroscopes and three-axis accelerometers, respectively. The micro-oven control system provides thermal isolation from the surrounding environment using a micro-machined isolation platform, vacuum-sealing, and a metal package. In addition, a CMOS temperature sensor, a proportional-integral-derivative-based temperature control scheme, and least mean square and random forest compensation algorithms are utilized to reduce temperature-induced bias drifts of IMUs. The most stable axes achieve peak-to-peak bias drifts of 12.78°/h and 665.2 ug during a thermal-cycle test for gyroscopes and accelerometers, respectively. The oven's heater power consumption is

We report a novel stacked balanced resonator structure and present the design of MEMS pitch/roll gyroscopes that utilize this stacked resonator. In this structure, two similar device layers are stacked, thus providing a balanced vertical resonator with significantly reduced anchor loss for out-of-plane (Le., the plane where the two resonators are attached) motion. Reducing the anchor loss allows one to increase the thickness of resonator layers, which leads to smaller thermoelastic dissipation and larger effective mass. A large-scale model of a stacked resonator is fabricated and tested, which proves that out-of-plane $Q$ can be improved by $>50\times$ when resonators are stacked. The design of a new stacked pitch/roll gyroscope is also presented and our analysis shows that this novel design could potentially provide noise of $\sim 1.5\times 10^{-10\circ}/\surd \mathrm{hr}$ .

Laser self-mixing interferometry (SMI), as an alternative contactless displacement measurement method, has extremely high resolution (pico-meter), large dynamic range and wide bandwidth. Comparing to electrostatic capacitive sensing, its detection accuracy does not depend on the gap size, electrode area, or bias voltage, which are bottlenecks for high-performance vibrating sensors. This paper presents our initial study in measuring vibrations of 3D shell resonators by laser self-mixing interferometry for application in high-performance gyroscopes. Our measurement of vibrations of a shell resonator using a VCSEL shows a noise-equivalent displacement resolution of 329pm with 100Hz bandwidth for resonator vibration amplitudes of less than 100nm, which can be improved down to $\pmb{2.2}\mathbf{pm}/\surd\mathbf{Hz}$ using low noise voltage amplifiers. If used with a fused silica shell resonator gyroscope, a rate resolution of 0.45 mdeg/hr with 1Hz bandwidth can be expected. To expand sensor dynamic range, a real-time, high-accuracy phase unwrapping technique is proposed. The scale factor of the SMI can be optimized in real time through mid-fringe point tracking by a positioning actuator.

The fabrication of shell resonators for vibratory gyroscopes is often accompanied by a split between drive and sense mode frequencies. To tune these frequencies and reduce the frequency split, a voltage can be applied between the shell and electrodes placed around it. This paper investigates electrostatic frequency tuning in shell resonators as a function of voltage, capacitive gap between the shell and electrode, electrode span angle and height, and electrode placement and configuration using a numerical approach. The results of this investigation show that conformal electrodes placed around the shell rim with a uniform gap provide the best tuning capability. Considering fabrication challenges and shell aspect-ratio, other electrode configurations might be more practical in some devices, although they have worse tuning capability.

We report a vacuum-packaged fused-silica (FS) micro birdbath shell resonator gyroscope (BRG) with near-navigation-grade in-run (evaluation duration $ day) bias stability of 0.0103 deg/h (at room temperature without temperature stabilization). The BRG utilizes a 5mm diameter birdbath (BB) resonator with $n=2$ wineglass mode $f=10.5436\ \mathrm{kHz}$ and original frequency split $(\Delta f)=6\ \text{Hz}$ :. The BRG is encapsulated in an LCC package and has an excellent $Q$ (1.54 million) and decay time constant $(r=46\ \mathrm{s})$ after near mode matching. The performance is believed to be limited by the noise from readout-and-control circuitry. The bias stability of this device is among the best reported values for micro-scale vibratory gyroscopes today.

In this work we report an improved design and method for fabrication of precision shell integrating (PSI) resonators for gyroscopes. PSI resonators are designed for lower thermomechanical noise and higher shock tolerance. We demonstrate fused silica (FS) micro-shell resonators with tailored sidewall thickness to tune the stiffness and mass of different regions in the resonators. PSI resonators of 10 mm diameter are demonstrated with low frequency split (1.2 Hz), high Q (7.5 million) and long ring-down time (6 minutes). The resonator's sidewall thickness is tailored to achieve large effective mass (>8 mg) and obtain $n=2$ wine-glass mode frequency at 6–7 kHz for immunity to vibrations. The shells were successfully tested for survivability under 7000g shock. These parameters are critical in achieving near navigation-grade performance ( $\text{ARW} , Bias Instability < 1mdeg/hr) for a MEMS gyroscope.

MEMS micro-hydraulic structures for amplification of force or deflection are introduced. These structures are integrated with capacitances to form electrostatic micro-hydraulic actuators (EMA). Hydraulic amplification and liquid permittivity are used to create stand-alone, efficient, and large deflection, and high force actuators. Force is generated using electrostatics with no need for external pressure sources. Use of integrated electrostatic force significantly reduces the device size. Utilizing this concept, a micro-valve and two types of EMA micro-piston arrays (water-based and silicone oil-based) are fabricated and tested. The micro-valve can switch fluid flows with the pressure ranging from 10 to 50 kPa at a maximum flow conductance of 20.3 sccm at 10 kPa with an actuation voltage of 340 $V_{\mathrm{ DC}}$ or 120 $V_{\mathrm{ AC}}$ . The silicone oil based micro-hydraulic micro-piston array has shown a maximum out-of-plane deflection of about 100 $\mu \text{m}$ at 210 $V_{\mathrm{ DC}}$ , and a maximum bandwidth of about 5 Hz with a foot print size of 0.16 cm2 and a maximum power consumption of 20 $\mu \text{W}$ at 1 Hz. These devices are the smallest ever reported micro-hydraulic systems that include the actuation source. [2015–0257]

In this paper, we present the design, fabrication and resonance characteristic of an axisymmetric 3D birdbath shell resonator operating in the n=3 wine-glass mode. Long ring-down time constant of 93 seconds, high quality factor of 10 million at nearly 34 kHz frequency, and large effective mass of 12.34 mg is achieved in the n=3 mode. This mode of operation has the potential to give lower noise performance as compared to the n=2 mode for a shell with similar quality factor. The resonator presented in this research can lead to a high performing navigation-grade MEMS gyroscope.

We present the design, fabrication, and measurement results of an axisymmetric 3D micro-shell resonator called the birdbath resonator. Three classes of birdbath resonators are studied; all exhibiting a record performance in terms of high-quality factor and long ring down time constants for their sizes. We also show that such high performing resonators have the potential to achieve low angle random walk and bias instability, achieving navigation-grade performance.

This paper presents a precision shell integrating (PSI) gyroscope design and fabrication based on an upfront simulation of a modified micro-blowtorching technique. The PSI resonator is designed to achieve low frequency n = 2 wine-glass mode and high parasitic mode frequencies to improve shock and vibration tolerance. The resonator has also larger effective mass than other MEMS gyroscope resonator designs. A non-isothermal model is developed to simulate reflow molding dynamics and solve the key challenge of PSI resonator fabrication, which is designing a patterned substrate geometry whose various regions stretch to the desired final thickness and land at the appropriate locations along a graphite mold. Our upfront process simulation model saves significant cost and time by eliminating the trial-and-error approach to fabricating PSI resonators with the desired mass and stiffness distribution.

MEMS gyroscopes are known to be susceptible to environmental factors, including temperature and stress. Many studies have shown various methods to reduce the effects of these factors, of which introducing a mechanical isolation platform has been proven the most effective. In this paper, we study three design considerations for a thermal and stress isolation platform for inertial sensors: resonant frequency, stress-relieving ability, and thermal resistance. The isolation platform design is then optimized to minimize stress effects and thermal losses. Experimental results show that the isolation platform reduces the stress sensitivity of commercial gyroscopes by a factor of 92x on the most effective axis and increases thermal resistance to around 1,100 K/W.

This paper presents the design and experimental results of a microvibratory actuation and sensing platform to provide on-chip physical stimulus for in situ calibration of long-term scale factor drifts in multiaxis microelectromechanical systems (MEMS) inertial sensors. The platform consists of a three degrees-of-freedom micromotion stage that can provide piezoelectric actuation for X / Y -tilting reference stimuli, compensation of undesired off-axis motion, integrated sensing of applied periodic stimulus, and electrostatic position lock-down for shock protection. A dual-axis MEMS gyroscope is mounted on top of the microplatform, and its electrical interconnects are provided through microfabricated highly flexible parylene cables with virtually zero-loading. The piezoelectric stage is measured to provide up to 280°/s angular ac excitation to a 25-mg inertial sensor payload at an expense of

Time synchronization is a vital feature in many wireless sensor networks with applications ranging from structural health monitoring systems to body area sensors used for rehabilitation and sport medicine. While different wireless protocols have been utilized in sensor networks, Bluetooth Low Energy (BLE) has drawn a lot of attention in the past years due to its low-power architecture and availability in many consumer electronics. Moreover, the added non-connectable beacon mode has increased its functionality for Internet of Things (IoT) and sensor fusion. However, in this mode as devices are not paired with each other no synchronization service is available. In this paper, we present a synchronization protocol based on BLE beacons that can be used in conjunction with BLE software stacks provided with a commercial Bluetooth System-on-Chip (SoC). Offset and frequency-drift estimation techniques are discussed, and the effects of number of synchronization packets and their intervals on the overall synchronization accuracy are investigated. Experimental results show that without any re-synchronization in ten minutes, average synchronization errors of less than 350 ns per minute (single hop) can be achieved.

The fused silica birdbath (BB) resonator is an axisymmetric 3D shell resonator that could be used in high-performance MEMS gyroscopes. We report a record quality factor (0 for a 5-mm-radius resonator, which is expected to reduce gyroscope bias drift. We present measurement results for two sizes of resonators with long vibratory decay time constants (τ), high Qs, and low damping asymmetry (Δτ−1) between their n = 2 wine-glass (WG) modes. We find a reduction in damping for larger resonators and a correlation between higher Q and lower as well as evidence of a lower bound on Q for resonators with low damping asymmetry.

This paper describes a generic, ultra-low-noise transimpedance amplifier (TIA) for capacitive MEMS sensors. The TIA obtains both very low input referred current noise (5.12 fA/VHz) and wide dynamic range (123 dB) by employing a digitally-controlled floating resistor, a voltage-and-temperature tolerant current generator, and low-noise operational amplifier (op-amp). The floating resistor allows the amplifier to obtain excellent output linearity and obtain a wide dynamic range. An integrated digital controller of the current generator lowers the TIA noise by reducing the amount of fluctuation in the resistance of the floating resistor by eliminating the transmission of control voltages for the floating resistor through a bonding pad. A beta-multiplier current reference circuitry with a resistor with low temperature coefficient of resistance (TCR) generates bias current with very low sensitivity to variations in supply voltage and temperature. A two-stage Miller-compensated op-amp with optimized transistor dimensions is designed. The prototype chip was fabricated using a 0.18 μm standard CMOS process with 1.8 V supply voltage. The circuitry is evaluated with a high performance vibratory MEMS gyroscope and excellent bias stability (0.04 deg/h) is measured.

We report the latest experimental results from a fused-silica Birdbath Resonator Gyroscope (BRG) with a quality factor of 419k and a resonant frequency of 9030 Hz. The BRG and its readout/control system achieve an angle random walk (ARW) of 0.00126 deg/√hr and a bias stability of 0.0391 deg/hr. These results were obtained using a force-rebalanced control architecture without temperature control or additional compensation. The ARW and bias stability are further improved by driving the resonator at displacements near 10% of the nominal electrostatic gap. The low gyroscope noise is attributed to a relatively large measured scale factor of 100 mV/deg/s.

This paper reports characterization of a micro actuation and sensing platform for on-chip scale factor measurement and calibration of generic MEMS inertial sensors. The platform has a unique 6-DOF-motion capability that is used to deliver calibration stimuli with minimum off-axis motion, simultaneous excitation of multiple calibration axes, and on-chip measurement of acceleration sensitivities of the tested IMU. The microsystem is demonstrated to provide rotational calibration references with less than 15–30 ppm short-term instability for characterization of scale factor of a commercial gyroscope load in its full sensing range.

Advances in energy harvesting systems are needed to power wireless sensors for structural health monitoring. Research on developing a harvesting system that converts the low frequency, non-periodic, and low-acceleration vibrations present on bridges is continued and significantly extended in this work. The mechanics of the harvester were optimized to increase its robustness and lifetime, power electronics were added, and the complete system was installed on the New Carquinez suspension bridge in California. The complete results and analysis are presented in this study. The power management circuit is added to rectify and boost the low AC output of the harvester and convert it into a usable DC voltage. The harvester design is further enhanced to significantly improve performance and robustness. During short-term on-bridge testing, the system was able to charge a 10 μF capacitor to 2 V DC, and the average harvester output power ranges from 1.6 to 5.0 μW, depending on the location on the bridge, a 10× improvement over previous results. A long-term test of the harvesting system has been conducted, during which the performance of the system was monitored remotely using a wireless sensor network. The system improvements described in this study enabled continuous operation in the harsh bridge environment for 13 months starting April 30, 2012 and constitute a major milestone in the development of miniaturized motion harvesters. Finally, the system was retrieved and analyzed to understand and verify the cause of observed long-term performance changes.

We present a 3-D fused-silica micro-scale shell gyroscope, called the birdbath resonator gyroscope (BRG). The BRGs axisymmetric geometry leads to a good frequency and Q symmetry. The birdbath resonator can be fabricated with a good structural symmetry because its anchor is self-aligned to the rest of the structure. The BRG has n=2 wine-glass modes at 10.5 kHz and has a large frequency separation between the n=2 wine-glass modes and the closest parasitic mode (|fparasitic-fn=2|/fn=2=0.3), which will potentially lead to a low vibration sensitivity. The equations of motion for 3-D shell gyroscopes are derived and the effective mass and angular gain of the BRG is estimated using finite element method (FEM). The BRG is fabricated using a 3-D micrometer-blow-torching process and assembly on an electrode substrate made with the silicon-on-glass process. The BRG is operated in the force-rebalance mode at vacuum at room temperature and has a scale factor of 27.9 mV/(deg/s), a full-scale range , an angle random walk of 0.106 deg/√h, and a bias stability of 1 deg/h. A large angular gain (0.317) is measured, which is close to the estimated value of 0.25 obtained via FEM.

This paper presents a new and simple microfabrication process for creating various 3-D microstructures with high-aspect ratios . The key feature of this process is the use of a blow torch, which provides very intense localized heat for a short amount of time . The flame temperature can be up to 2500 °C for a propane-oxygen torch, above the melting temperatures of many high- Q materials. We demonstrate the fabrication of hemispherical and half-toroid (birdbath) shells from 100- μm-thick fused silica substrates. The structures have an rms surface roughness of 5.3 Å, which is crucial for achieving both high mechanical and optical Q. We create microbirdbath resonators by batch-level releasing the birdbath shells. We verify the resonance mode shapes of the degenerate n=2 wineglass modes using laser vibrometry and measure the frequency and Q of these modes using laser vibrometry and a capacitive measurement method. We demonstrate one of the best mechanical Q and smallest frequency split between the n=2 wineglass modes among existing micromechanical resonators. The birdbath resonator is promising for emerging applications such as the microrate-integrating gyroscope.

This paper analyzes potential causes of vibration-induced error in ideal MEMS tuning fork gyroscopes. Even though MEMS gyros are known to be highly susceptible to mechanical vibration, the mechanisms responsible for generating vibration-induced errors are not well understood. We focus on the tuning fork gyroscope (TFG) design that is known to be relatively immune to vibration because of its differential operation and common-mode rejection. Our analysis, however, demonstrates that even an ideal TFG cannot completely eliminate vibrations in special situations because of vibration-induced asymmetry and nonlinearity. We identify three major causes of error that arise from (1) capacitive nonlinearity at the sense electrode, (2) asymmetric electrostatic forces along sense direction at the drive electrodes, and (3) asymmetric electrostatic forces (i.e., drive-electrode capacitance) along drive direction at the drive electrodes. The occurrence conditions and characteristics of each cause are analyzed. The effects of the causes on three classes of TFG gyro designs are analyzed and compared both qualitatively and quantitatively using dynamic analysis and simulation. Interestingly, in our simulation conditions, one TFG design (denoted as Type-DD) is less sensitive to vibration (>99% reduction) than the other two TFG designs (denoted as Type-CP and Type-DS). The reason for this difference is that Type-DD gyroscopes are immune to the dominant cause of error afflicting Type-CP and Type-DS designs. Our analysis also demonstrates that the most critical error-generation condition is vibration along with the sense direction of gyroscopes (denoted as sense-direction vibration) because of its contribution to all causes of error.

The performance of a commercial 6-axis (3-axis accelerometer and 3-axis gyroscope) MEMS inertial measurement unit (IMU) has been improved by a factor of >300x by utilizing a low-power ovenized microsystem. The IMU is thermally isolated from the external ambient by mounting it on a custom-designed micro-machined glass platform and packaging it in vacuum. In the present study, a microcontroller and voltage-controlled current source are assembled together with the thermally-isolated packaged IMU on a printed circuit board. The entire system is thermal-cycled over a temperature span from −40°C to 85°C. Both temperature control (i.e., ovenization) and compensation are used to reduce bias drift due to temperature change. The measured frequency drift of the IMU is improved by a factor of 950x and stabilized to ±2ppm, and the bias drift of the IMU is reduced to 60 °/hr for one of the gyroscope axes, and 1.7 mg for one of the accelerometer axes.

This paper presents a detailed model for possible vibration effects on MEMS degenerate gyroscopes represented by vibratory ring gyroscopes. Ring gyroscopes are believed to be relatively vibration-insensitive because the vibration modes utilized during gyro operation are decoupled from the modes excited by environmental vibration. Our model incorporates four vibration modes needed to describe vibration-induced errors: two flexural modes (for gyro operation) and two translation modes (excited by external vibration). The four-mode dynamical model for ring gyroscopes is derived using Lagrange's equations. The model considers all elements comprising a ring gyroscope, namely the ring structure, the support-spring structures, and the electrodes that surround the ring structure. Inspection of this model demonstrates that the output of a ring gyroscope is fundamentally insensitive to vibration due to the decoupled dynamics governing ring translation versus ring flexure, however, becomes vibration-sensitive in the presence of non-proportional damping and/or capacitive nonlinearity at the sense electrodes.

Lithographically defined microelectrode arrays now permit high-density recording and stimulation in the brain and are facilitating new insights into the organization and function of the central nervous system. They will soon allow more detailed mapping of neural structures than has ever before been possible, and capabilities for highly localized drug-delivery are being added for treating disorders such as severe epilepsy. For chronic neuroscience and neuroprosthesis applications, the arrays are being used in implantable microsystems that provide embedded signal processing and wireless data transmission to the outside world. A 64-channel microsystem amplifies the neural signals by 60 dB with a user-programmable bandwidth and an input-referred noise level of 8 muVrms before processing the signals digitally. The channels can be scanned at a rate of 62.5 kS/s, and signals above a user-specified biphasic threshold are transmitted wirelessly to the external world at 2 Mbps. Individual channels can also be digitized and viewed externally at high resolution to examine spike waveforms. The microsystem dissipates 14.14 mW from 1.8 V and measures 1.4 1.55 cm2.

A new micro-Pirani vacuum gauge that employs a ladder-shaped structure with two parallel bridges and crosslinks in between has been designed and fabricated. This design enhances the physical performance of the gauge by increasing structural rigidity, thus allowing for longer beams and a wider selection of materials, and by allowing for better heat distribution across the sensor - therefore improving the full-scale range of sensor response. Furthermore, this Pirani gauge can be fabricated in a one-, two-, or three-mask process without postprocessing steps such as KOH etching. In a CMOS-compatible process, poly-Si 4 times 2 times 250-mum and 4 times 2 times 1000-mum Pirani gauges with the ladder structure were fabricated and tested with pressure ranges from 10-3 to 50 torr (0.133 to 1 times 103 Pa) and 5 times 10-2 to 760 torr (6.67 to 1.01 times 105-Pa atmospheric pressure) and with resolutions of approximately 10-3 and 5 times 10-2 (0.133 to 6.67 Pa), respectively. Constant temperature circuitry and thermoelectric temperature stabilization would further extend the range of operation and the resolution of these devices. Furthermore, these sensors operate at very low powers ranging from 300 to 600 muW depending on their geometry and pressure measurement range.

This paper reports a MEMS vacuum package with vertical feedthroughs formed in a glass substrate all at the wafer level. This approach satisfies requirements for MEMS vacuum packages, including small size, vacuum/hermetic capability, sealed and low parasitic feedthroughs, wafer-level processing, compatibility with most MEMS processes, and low cost. It also enables flip-chip solder attachment to a PC board. The package has an integrated micro-Pirani gauge on a glass substrate for in situ monitoring, a silicon cap, and vertical feedthroughs through the glass. The integrated Pirani gauge has 0.6 milli-torr resolution at 0.1 torr and 0.2 torr resolution at 100 torr. Using the Pirani gauge, the fabricated vacuum package is characterized. The package has maintained ~33 torr base pressure with plusmn1.5 torr uncertainty for more than four months without a getter. The long-term measured pressure uncertainty is from the measurement setup and environment, and can be improved using a getter inside the package. [2007-0160]

The emergence of accurate MEMS inertial sensors motivates the design of miniature inertial measurement units (IMU) for applications well outside the field of inertial navigation. One promising application concerns novel sports training systems with inertial sensors embedded directly in sports equipment. This paper describes the theory, design, and evaluation of a miniature, wireless IMU that precisely measures the dynamics of a golf club used in putting. The design consists of a complete six degree-of-freedom IMU composed of MEMS accelerometers and angular rate gyros with an integrated microprocessor and RF transceiver. The resulting sensor system has negligible mass (25 g relative to 490 g for the putter) and is a mere 13 mm in diameter allowing it to fit wholly within the shaft of the club at the grip end. The measurement theory enables the computation of the position, velocity, and orientation of the club head at the opposite end of the shaft during the entire putting stroke. Experiments reveal that the three-dimensional position and orientation of the club head can be resolved to within 3 mm and 0.5°, respectively. These achievements yield a highly accurate, portable, and inexpensive sensor system to support golf swing training, custom club fitting, and club design.

This paper reports a wafer-level transfer technique for forming thin, flexible, and freestanding parylene membranes. Parylene thin films (~1.3 mum) have been successfully transferred from one wafer to another to form a freestanding membrane encapsulating over wide and shallow cavities (< 5 mum deep and 2000 times 2000 mum2 square) with fine alignment (< 3.0 mum) and 87% yield. Transferred membranes may be a composite of parylene/metal/parylene, contain through-hole patterns of diverse size (5 times 5 ~ 2000 times 2000 mum2), have mild tension (1.14 MPa), and remain freestanding and flat through various standard post-transfer microfabrication processes such as photolithography, evaporation, and wet etching. They also provide excellent sealing against pressure of up to 20 kPa and long-term stability over repeated deflection. This paper focuses on two areas: (1) the study of issues involving optimum transfer conditions, minimum achievable gap between transferred membranes and device wafers, patterned-film and composite-layer transfer, and aligned transfer; and (2) the characterization of the post-transfer membrane properties, including stress/tension, sealing capability, effects of post-transfer processing, and long-term stability after a repeated deflection.

We report a new fabrication technology for making fused silica (FS) wineglass resonators with arbitrarily sized FS solid stems through a simultaneous process of micro blow-torching and microwelding. The process allows the welding of multiple FS structures at controlled locations during blow torching. We demonstrate a new micro FS wineglass resonator with high quality factor (Q) and long ring down time (τ). The resonator is formed by blow torching and flowing a thin FS substrate using vacuum to form the resonator shell, and by welding the shell to a solid post at a controlled location. The flowing of the shell and welding to the rod is performed in one step and in a single mold. This solid-stem resonator offers low anchor loss due to the large stem length/stiffness, and small shell rim thickness. The device has a shell radius/height of ∼2.8 mm, and a stem radius of 0.5 mm. At

This paper explores polycrystalline 3C-silicon carbide (poly-SiC) deposited by LPCVD for fabricating flexible ribbon cable interconnects for micromachined neural probes. While doped silicon is used currently, we hypothesized that poly-SiC will provide enhanced mechanical robustness due to SiC’s superior mechanical properties. Paralleling prior work in silicon, forty-two different designs were fabricated from nitrogen-doped poly-SiC films deposited by LPCVD at 900°C using dichlorosilane and acetylene as precursors. The different designs were then tested in bending and twisting modes. Curved beams were found to bend nearly 250% more than straight beams before fracture. Longer beams withstood greater bending and twisting due to greater compliance. Longer and narrower beams generally outperformed shorter beams irrespective of design. Also, doped poly-SiC beams had, on average, breaking angles that were greater than those of identical doped silicon beams by ~50% in bending and ~20% in twisting modes. The paper details the designs studied, describes the fabrication process for the test structures and compares/contrasts the testing and simulation results related to the different designs to identify best design practices.

Axisymmetric shell resonators have been attractive candidates for high performance MEMS vibratory gyroscopes because of their high quality factor, low sensitivity to environmental vibrations and electrostatic tuning capability. Fused silica shell resonators made by blow torch molding with high quality factor could perform as high performance MEMS gyroscopes. Despite such advantageous features, the performance of these shell resonators is limited by geometric imperfections that occur during fabrication. This paper investigates effect of geometric asymmetries such as height and radius imperfections, notch, and mass imbalance in the rim of gyroscopes on the split in natural frequencies of the n=2 wineglass modes. Numerical simulation shows that perfect fused silica shell has 13929 Hz natural resonance frequencies without any frequency split. Analysis of imperfect shell reveals that frequency split is very sensitive to edge geometric imperfection and mass imbalance in the rim. On the other hand, Δf is not very sensitive to the notch in the rim of shell and height imperfection less than 40μm.Copyright © 2014 by ASME

This paper presents a four-channel telemetric microsystem featuring on-chip alternating current amplification, direct current baseline stabilization, clock generation, time-division multiplexing, and wireless frequency-modulation transmission of microvolt- and millivolt-range input biopotentials in the very high frequency band of 94-98 MHz over a distance of /spl sim/0.5 m. It consists of a 4.84-mm/sup 2/ integrated circuit, fabricated using a 1.5-/spl mu/m double-poly double-metal n-well standard complementary metal-oxide semiconductor process, interfaced with only three off-chip components on a custom-designed printed-circuit board that measures 1.7/spl times/1.2/spl times/0.16 cm/sup 3/, and weighs 1.1 g including two miniature 1.5-V batteries. We characterize the microsystem performance, operating in a truly wireless fashion in single-channel and multichannel operation modes, via extensive benchtop and in vitro tests in saline utilizing two different micromachined neural recording microelectrodes, while dissipating /spl sim/2.2 mW from a 3-V power supply. Moreover, we demonstrate successful wireless in vivo recording of spontaneous neural activity at 96.2 MHz from the auditory cortex of an awake marmoset monkey at several transmission distances ranging from 10 to 50 cm with signal-to-noise ratios in the range of 8.4-9.5 dB.

A propulsion system based on acoustic streaming generated by Helmholtz resonators is presented. High frequency (>60 kHz) electrostatically driven micromachined Helmholtz resonators constitute the basic unit of the system. Microjets produced at the exit of these resonators can be combined to form a distributed propulsion system. A high yield (>85%) fabrication process is introduced for fabrication of individual as well as arrays of resonators. The fabrication results for ten different designs are presented. About 1000 resonators of similar design cover the surface of a 4-in. wafer, effectively converting it to a distributed propulsion system. A number of characterization methods such as monitoring the harmonics of the drive current, laser interferometry, hot-wire anemometry, acoustic spectrum measurement and video particle imaging are used to determine the structural and fluidic behavior of different resonator designs. Collapse and recovery times of the diaphragm in the electrostatic actuator of the resonator are characterized and reduced to less than 10 μs by optimizing the perforation design. The occurrence of acoustic streaming in the micron-scale is verified via video particle imaging. The jet streams produced with pulse drive at low frequencies (~1 kHz) are spatially profiled and jet velocities exceeding 1 m/s are measured at the exit of the resonators. It has been verified that the resonance frequencies of the device at 50 and 175 kHz can be closely predicted by modeling.

A novel propulsion method suitable for micromachining is presented that takes advantage of Helmholtz resonance, acoustic streaming, and eventually flow entrainment and thrust augmentation. In this method, an intense acoustic field is created inside the cavity of a Helmholtz resonator. Flow velocities at the resonator throat are amplified by the resonator and create a jet stream due to acoustic streaming. These jets are used to form a propulsion system. In this paper a system hierarchy incorporating the new method is described and the relevant governing equations for the Helmholtz resonator operation and acoustic streaming are derived. These equations can predict various device parameters such as cavity pressure amplitude, exit jet velocity and generated thrust. In a sample embodiment, an electrostatic actuator is used for generation of the initial acoustic field. The relevant design parameters for the actuator are discussed and an equivalent circuit model is synthesized for the device operation. The circuit model can predict the lowest order system resonance frequencies and the small signal energy conversion efficiency. A representative resonator performance is simulated and it is shown that velocities above 16 m/s are expected at jet nozzles. The calculated delivered thrust by this resonator with 0.7 μm diaphragm displacement amplitude is 3.3 μN at the resonance frequency.

A new CMOS current source is described for biomedical implantable microstimulator applications, which utilizes MOS transistors in deep triode region as linearized voltage controlled resistors (VCR). The VCR current source achieves large voltage compliance, up to 97% of the supply voltage, while maintaining high output impedance in the 100 M/spl Omega/ range to keep the stimulus current constant within 1% of the desired value irrespective of the site and tissue impedances. This approach improves stimulation efficiency, extends power supply lifetime, and saves chip area especially when the stimulation current level is high in the milliampere range. A prototype 4-channel microstimulator chip is fabricated in the AMI 1.5-/spl mu/m, 2-metal, 2-poly, n-well standard CMOS process. With a 5-V supply, each stimulating site driver provides at least 4.25-V compliance and >10 M/spl Omega/ output impedance, while sinking up to 210 /spl mu/A, and occupies 0.05 mm/sup 2/ in chip area. A modular 32-site wireless neural stimulation microsystem, utilizing the VCR current source, is under development.

This paper presents Interestim-2B, a modular 32-site wireless microstimulating ASIC for neural prosthesis applications, to alleviate disorders such as blindness, deafness, and severe epilepsy. Implanted just below the skull along with a high-density intracortical microelectrode array, the chip enables leadless operation of the resulting microsystem, accepting power and data through an inductive link from the outside world and inserting information into the nervous system in the form of stimulating currents. Each module contains eight current drivers, generating stimulus currents up to /spl plusmn/270 /spl mu/A with 5-b resolution, /spl sim/100M/spl Omega/ output impedance, and a dynamic range (headroom voltage) that extends within 150 mV of the 5 V supply rail, and 250 mV of the ground level. As many as 64 modules can be used in parallel, to drive multiprobe arrays of up to 2048 sites, with only a pair of connections to a common inductive-capacitive (LC) tank circuit, while receiving power (8.25 mW/module) and data (2.5 Mb/s) from a 5/10-MHz frequency shift keyed carrier. Every 4.6 mm /spl times/ 4.6 mm chip fabricated in a 1.5-/spl mu/m, 2M/2P standard CMOS process through MOSIS, houses two modules and generates up to 65 800 stimulus pulses/s.

This paper describes the design and implementation of fully integrated rectifiers in BiCMOS and standard CMOS technologies for rectifying an externally generated RF carrier signal in inductively powered wireless devices, such as biomedical implants, radio-frequency identification (RFID) tags, and smartcards to generate an on-chip dc supply. Various full-wave rectifier topologies and low-power circuit design techniques are employed to decrease substrate leakage current and parasitic components, reduce the possibility of latch-up, and improve power transmission efficiency and high-frequency performance of the rectifier block. These circuits are used in wireless neural stimulating microsystems, fabricated in two processes: the University of Michigan's 3-/spl mu/m 1M/2P N-epi BiCMOS, and the AMI 1.5-/spl mu/m 2M/2P N-well standard CMOS. The rectifier areas are 0.12-0.48 mm/sup 2/ in the above processes and they are capable of delivering >25mW from a receiver coil to the implant circuitry. The performance of these integrated rectifiers has been tested and compared, using carrier signals in 0.1-10-MHz range.

A vertical actuator fabricated using a trench-refilled-with-polysilicon (TRiPs) process technology and employing an array of vertical oriented comb electrodes is presented. This actuator structure provides a linear drive to deflection characteristic and a large throw capability which are key features in many sensors, actuators and micromechanisms. The actuation principle and relevant theory is developed, including FastCap simulations for theoretical verification. Design simplifications have been suggested that enable one to use parallel plate analytical expressions which match simulation results with /spl sim/5.6% error. Several actuators were designed and fabricated using the 7-mask TRiPs technology with calculated drive voltages as low as 45 V producing 10 /spl mu/m of deflection. The actuators employed a mechanical structure that was 18 /spl mu/m tall using a polysilicon layer 1.5 /spl mu/m thick and occupying a total area of 750 /spl mu/m by 750 /spl mu/m. The actuators were successfully tested electrostatically and several microns of deflection were observed.

This paper presents the design and preliminary test results of a micro actuation and sensing platform to provide on chip physical stimulus for in situ calibration of long-term drifts in scale factor and offset of dual-axis MEMS gyroscopes. The platform consists of a 3-DOF micro vibratory stage that can provide piezoelectric actuation for X/Y-tilting reference stimuli, off-axis motion compensation, analog sensing of applied periodic stimulus, and electrostatic position lockdown for shock protection. Initial characterizations are performed with a commercial MEMS gyroscope (25 mg) mounted on top of the micro motion platform, while its electrical interconnects provided through microfabricated highly-flexible parylene cables. The piezoelectric stage is measured to provide up to 220 degree/sec angular AC excitation, while providing an analog sensing signal to determine the applied stimulus with a precision of 1.2 degree/sec. The estimated scale factor has

We present the fused-silica micromachined birdbath resonator gyroscope (μ-BRG) operating in the whole-angle (WA) mode. The key advantages of the whole angle mode operation is rotation angle measurement, large bandwidth, and full-scale range which is needed in detecting the motion of fast-moving objects. The μ-BRG is made with fused silica using a micro blow-torching process and has n = 2 wineglass modes at 10.46 kHz with a small frequency mismatch (Δf = 10 Hz) and a decay time (τ) of 2.2s. The WA-BRG achieves a stable angular gain (Ag) and a large full scale range (700°/s).

This paper presents the design, fabrication, and testing of an 80-/spl mu/m-thick, 1.1 mm in diameter high aspect-ratio (20:1) polysilicon ring gyroscope (PRG). The vibrating ring gyroscope was fabricated through the high aspect-ratio combined poly and single-crystal silicon MEMS technology (HARPSS). This all-silicon single-wafer technology is capable of producing electrically isolated vertical electrodes as tall as the main body structure (50 to 100's (/spl mu/m tall)) with various size air-gaps ranging from submicron to tens of microns. A detailed analysis has been performed to determine the overall sensitivity of the vibrating ring gyroscope and identify its scaling limits. An open-loop sensitivity of 200 /spl mu/V/deg/s in a dynamic range of /spl plusmn/250 deg/s was measured under low vacuum level for a prototype device tested in hybrid format. The resolution for a PRG with a quality factor (Q) of 1200, drive amplitude of 0.15 /spl mu/m, and sense node parasitic capacitances of 2 pF was measured to be less than 1 deg/s in 1 Hz bandwidth, limited by the noise from the circuitry. Elimination of the parasitic capacitances and improvement in the quality factor of the ring structure are expected to reduce the resolution to 0.01 deg/s/(Hz)/sup 0.5/.

This paper presents an implantable microsystem for tonometric blood pressure measurement in small animals. The microsystem consists of four major components: (1) a titanium base for supporting a pressure sensor and an interface chip, (2) a micromachined capacitive pressure sensor array, (3) a switched-capacitor interface chip, and (4) a titanium cap. A new micromachining fabrication process has been developed to create capacitive pressure transducers with a flat surface necessary for tonometric pressure measurement. An array of three capacitive sensors is used to increase signal output and improve stability. A custom-designed switched-capacitor CMOS interface circuit is used to measure changes in capacitance. In vitro calibration tests have been performed on the complete cuff using a silastic tube to mimic a pliable blood vessel. A sensitivity of 2 mV/mmHg @ 100 mmHg and a resolution of 0.5 mmHg (based on 1 mV RMS interface chip noise floor) has been obtained. The dimensions of the cuff system 10(L)×6.5(W)×3(H) mm3.

This paper presents a generic low-power sensor interface chip compatible with smart microsystems and a wide range of capacitive transducers. The interface chip is highly programmable, can communicate with an external microcontroller using a nine-line sensor bus standard, contains a switched-capacitor readout circuit, supports sensor self-test, and includes a temperature sensor. The circuit can interface with up to six external sensors and contains three internal programmable reference capacitors in the range of 0.15–8 pF. The chip measures 3.2×3.2 mm in a standard 3-μm single-metal double-poly p-well process, dissipates less than 2.2 mW from a single 5 V supply, and can resolve input capacitance variations of less than 1 fF in 10 Hz bandwidth.

This paper describes the development of a micromachined silicon platform fabricated using the dissolved wafer process that supports: (1) high self-resonance frequency and quality factor inductors suspended on a dielectric membrane, (2) low-loss thin-film capacitors, and (3) polysilicon resistors. The process uses deep boron diffusion to create silicon anchors, which support a stress compensated dielectric membrane. A thick resist mold is used to gold electroplate the inductor, top capacitor plate, and bonding pads. This platform can be used to build miniature high-performance transceivers or other RF subsystems using either hybrid-attached surface-mount components or flip-chip bonded RF circuits. Using this technique, a Colpitts transmitter with a five-turn dielectric suspended inductor was designed and fabricated. The transmitter oscillates in the frequency band of 275-375 MHz, consumes 200 µA when operated continuously and 100 µA when amplitude modulated (on-off keying) at a rate of 1 Mbps (50% duty cycle).

This paper reports the development of an implantable, fully integrated, multichannel peripheral neural recording system, which is powered and controlled using an RF telemetry link. The system allows recording of /spl plusmn/500 /spl mu/V neural signals from axons regenerated through a micromachined silicon sieve electrode. These signals are amplified using on-chip 100 Hz to 3.1 kHz bandlimited amplifiers, multiplexed, and digitized with a low-power (