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Author(s): Chen, Yongtai; Tang, William C; Chu, Jinkui; Zhang, Ran; Li, Song | Abstract: An accurate sky polarization field map is a prerequisite for polarization navigation applications. In this article, a detector for sky full-polarization imaging detection is described, the major error-influencing factors (MEIFS ) are obtained, and the error propagation is modeled and analyzed. We reveal the relationship between the error of the inversed Stokes vector and the condition number of the detector matrix, which shows that the error of the inversed Stokes vector is affected by the Stokes vector of the incident light itself and the MEIFS together, with the MEIFS playing a decisive role. With the MEIFS optimized, the impact of detector error on the inversed Stokes vector is attenuated. A control equation for system calibration is also deduced which can establish the connection between the detector matrix design and calibration process. The work in this article provides a reference for optimization and calibration of sky full-polarization imaging detectors.

Activity selection is critical for the smart environment and Cyber-Physical Systems (CPSs) that can provide timely and intelligent services, especially as the number of connected devices is increasing at an unprecedented speed. As it is important to collect labels by various agents in the CPSs, crowdsourcing inference algorithms are designed to help acquire accurate labels that involve high-level knowledge. However, there are some limitations in the algorithm in the existing literature such as incurring extra budget for the existing algorithms, inability to scale appropriately, requiring the knowledge of prior distribution, difficulties to implement these algorithms, or generating local optima. In this paper, we provide a crowdsourcing inference method with variational tempering that obtains ground truth as well as considers both the reliability of workers and the difficulty level of the tasks and ensure a local optimum. The numerical experiments of the real-world data indicate that our novel variational tempering inference algorithm performs better than the existing advancing algorithms. Therefore, this paper provides a new efficient algorithm in CPSs and machine learning, and thus, it makes a new contribution to the literature.

Background Music therapy improves neuronal activity and connectivity of healthy persons and patients with clinical symptoms of neurological diseases like Parkinson’s disease, Alzheimer’s disease, and major depression. Despite the plethora of publications that have reported the positive effects of music interventions, little is known about how music improves neuronal activity and connectivity in afflicted patients. Methods For patients suffering from Parkinson’s disease (PD), we propose a daily 25-min music-based synchronous finger tapping (SFT) intervention for 8 weeks. Eligible participants with PD are split into two groups: an intervention group and a control arm. In addition, a third cohort of healthy controls will be recruited. Assessment of finger tapping performances, the Unified Parkinson’s Disease Rating Scale (UPDRS), an n-back test, the Montreal Cognitive Assessment (MoCA), as well as oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (HbR), and total hemoglobin activation collected by functional near-infrared spectroscopy (fNIRS) are measured at baseline, week 4 (during), week 8 (post), and week 12 (retention) of the study. Data collected from the two PD groups are compared to baseline performances from healthy controls. Discussion This exploratory prospective trial study investigates the cortical neuronal activity and therapeutic effects associated with an auditory external cue used to induce automatic and implicit synchronous finger tapping in patients diagnosed with PD. The extent to which the intervention is effective may be dependent on the severity of the disease. The study’s findings are used to inform larger clinical studies for optimization and further exploration of the therapeutic effects of movement-based music therapy on neural activity in neurological diseases. Trial registration ClinicalTrials.gov NCT04212897. Registered on December 30, 2019. The participant recruitment and study protocol have received ethical approval from the First Affiliated Hospital of Dalian Medical University. The hospital Protocol Record number is PJ-KY-2019-123. The protocol was named “fNIRS Studies of Music Intervention of Parkinson’s Disease.” The current protocol is version 1.1, revised on September 1, 2020.

Background: Music therapy improves neuronal activity and connectivity of healthy persons and patients with clinical symptoms of neurological diseases like Parkinson’s Disease, Alzheimer’s Disease, and Major Depression. Despite the plethora of publications that have reported the positive effects of music interventions, little is known about how music improves neuronal activity and connectivity in afflicted patients. In this three-part series of studies, each of the three neurological disorders – (1) Parkinson’s Disease, (2) Alzheimer’s Disease, and (3) Major Depression – will be treated individually in detail. Methods: For patients suffering from Parkinson’s Disease (PD), we propose a daily 25-minute music-based synchronous finger tapping (SFT) intervention for 8-weeks. Participants will be each split into two groups: an intervention group and a control arm. Assessment of finger tapping performances, the Unified Parkinson’s Disease Rating Scale (UPDRS), an n-back test, the Montreal Cognitive Assessment (MoCA), as well as oxygenated- (HbO 2 ), deoxygenated- hemoglobin (HbR), and total hemoglobin activation collected by functional near-infrared spectroscopy (fNIRS) will be measured at baseline, week 4 (during), week 8 (post), and week 12 (retention) of the study. Data collected from the two PD groups will be compared to baseline performances from healthy controls.Discussion: The trial study investigates the cortical neuronal activity and therapeutic effects associated with an auditory external cue used to induce automatic and implicit synchronous finger tapping in patients diagnosed with PD. The extent to which the intervention is effective may be dependent on the severity of the disease.

With the fast growing of artificial intelligence (AI), more and more applications require querying uncertain data, especially from social media and crowd sourcing platform. In situations where it is impossible to increase data quality by controlling the sources, we may resort to algorithms to make the best use of the collected data. Since crowdsourcing provides a useful way to distributing tasks to mass people, and collects labels from as many workers as possible, many researchers have been study crowd-sourcing inference algorithms. In our work, we propose a novel crowd-sourcing inference algorithm to infer ground truth and obtain worker reliability and task difficulty at the same time.

Objectives/Hypothesis Permanent facial nerve injury is a difficult challenge for both patients and physicians given its potential for debilitating functional, cosmetic, and psychological sequelae. Although current surgical interventions have provided considerable advancements in facial nerve rehabilitation, they often fail to fully address all impairments. We aim to introduce an alternative approach to facial nerve rehabilitation. Study Design Acute experiments in animals with normal facial function. Methods The study included three anesthetized cats. Four facial muscles (levator auris longus, orbicularis oculi, nasalis, and orbicularis oris) were monitored with a standard electromyographic (EMG) facial nerve monitoring system with needle electrodes. The main trunk of the facial nerve was exposed, and a 16-channel penetrating electrode array was placed into the nerve. Electrical current pulses were delivered to each stimulating electrode individually. Elicited EMG voltage outputs were recorded for each muscle. Results Stimulation through individual channels selectively activated restricted nerve populations, resulting in selective contraction of individual muscles. Increasing stimulation current levels resulted in increasing EMG voltage responses. Typically, selective activation of two or more distinct muscles was successfully achieved via a single placement of the multi-channel electrode array by selection of appropriate stimulation channels. Conclusion We have established in the animal model the ability of a penetrating electrode array to selectively stimulate restricted fiber populations within the facial nerve and to selectively elicit contractions in specific muscles and regions of the face. These results show promise for the development of a facial nerve implant system. Level of Evidence N/A.Laryngoscope, 2016 127:460–465, 2017

The top challenges for widespread application of ventricular assist device are infections of the driveline and pump thrombosis of the device. This project makes use of the powerful multiphysics computational simulation to improve the design of the left ventricular assist devices, by eliminating the driveline and streamlining the pump interior blood contacting surfaces. The design optimization involves balancing the wireless power transfer efficiency, implant miniaturization, and the regulatory compliance.

This paper presents a novel flexible implantable device to provide high-resolution mechanical strain data from a bone surface in real time. The design of the device has been verified with finite-element analysis, and a prototype has been successfully fabricated which consists of a thin-film metal gauge encapsulated between two layers of parylene-C. The prototype has been characterized simultaneously with a commercial strain gauge using tensile testing. The results indicated that the strain sensitivities of the prototype were approximately 2.5 times greater than those of commercial gauges. In addition, real-time strain data collection has been successfully demonstrated on bone surfaces with the novel devices using mechanical testing of chicken tibiae in three-point bending.

We present the first demonstration of single-walled carbon nanotube transistor operation at microwave frequencies. To measure the sourcedrain ac current and voltage at microwave frequencies, we construct a resonant LC impedance-matching circuit at 2.6 GHz. Both semiconducting and metallic nanotubes are measured. Varying the back-gate voltage for a semiconducting nanotube at dc varies the 2.6-GHz source-drain impedance. In contrast, varying the back-gate voltage on a metallic nanotube at dc has no effect on the microwave source-drain impedance. We find the ac source-drain impedance to be different than the dc source-drain resistance, which may be due to the distributed nature of the capacitive and inductive impedance of the contacts to the nanotube. The dynamical (ac) electrical properties of carbon nanotubes are technologically relevant for both active and passive devices made from carbon nanotubes. At dc, it is known that electrons can move without scattering over many micrometers inside a carbon nanotube. 1 We recently analyzed, from a theoretical point of view, the microwave passive 2,3 and active 4,5 electrical properties of nanotubes in some detail. The successful operation of a multiwalled carbon nanotube rf single-electron transistor was recently reported. 6 In this paper, we present the first measurements of the electrical properties of single-walled nanotubes at gigahertz frequencies. 7 In so doing, we demonstrate, for the first time

We report on the development of a micro-electro-mechanical systems (MEMS) valve that is designed to meet the rigorous performance requirements for a variety of space applications, such as micro-propulsion, in situ chemical analysis of other planets, or microbiology. These systems often require very small yet reliable silicon valves with extremely low leak rates and long shelf lives. Also, they must survive the perils of space travel, which include unstoppable radiation, monumental shock and vibration forces, as well as extreme variations in temperature. Currently, no commercial MEMS valve meets these requirements. At JPL, we are developing a piezoelectric MEMS valve that attempts to address the unique problem of space. We begin with proven configurations that may seem familiar. However, we have implemented some major design innovations that should produce a superior valve. The JPL micro-valve is expected to have an extremely low leak rate, limited susceptibility to particulates, vibration or radiation, as well as a wide operational temperature range.

This letter reports on the design, fabrication, and testing a new class of low-impedance multiple-frequency micromechanical resonator using piezoelectric transduction mechanism. The resonator is fabricated out of a 3-/spl mu/m-thick silicon layer on a silicon-on-insulator wafer with a low-temperature post-CMOS compatible process. Two types of low-impedance resonators using the same design principle are presented here. The center frequency of the novel resonator is set by the lithographically defined in-plane dimension of the device (width of bar or radius of disk). The 200-/spl mu/m-diameter disk-shaped resonator is measured to have an impedance of 1.6 k/spl Omega/ at the resonant frequency of 45.4 MHz, with a quality factor of 1100. The bar-type resonator is measured to have an impedance of 920 /spl Omega/ at 60 MHz, exhibiting a Q factor of 1400.

This paper presents the fabrication of a silicon based three dimensional intraneural electrode array. The electrode array consists of a 3 by 4 array of needles with a 250 μm center to center distance and 50 μm separation between neighboring needles. The length of each penetrating portion of the needle is defined by the starting silicon material thickness. We present the fabrication details to build 1 mm tall needles with 250 to 400 μm of their height insulated in SU-8. We are able to present a simpler, more elegant, more reproducible, and more scalable process than the current state of the art method that relies on glass insulation and a dicing saw by using deep reactive ion etching to produce needles and SU-8 to electrically isolate them.

We report on the design, fabrication, and test results of a set of microfluidic devices with channels designed to promote fluidic hydrodynamic forces to sort and separate cells based on cell sizes. A set of 14 devices were made from polydimethylsiloxane (PDMS) molded from photolithographically patterned SU-8. The spiral fluidic channels with specific numbers of turns, widths, and outer diameters were designed with branches at strategic locations along the length to divert separated particles into collection chambers. A mixture of polystyrene particles of two different diameters (7 and 20 μm) was used as the test solution to determine the sorting efficiencies. Theoretical analyses of the designed performance were based on previously published equations and were found to be within practical agreement. The optimized performance was consistently close to 90% capture and isolation efficiencies from a mixture of up to 1:100,000 of 20-μm-to-7-μm particles at a flow rate of 4.0 mL·min-1.

This paper presents a novel method for fabricating silicon based planer microelectrodes with SU-8 embedded fluidic channels. A 7 mm long neural probe was fabricated with a 5 mm penetrating shank and a 2 mm × 2 mm base. One surface of the probe consists of eight 160 μm diameter wire bonding pads connected to eight 60 μm diameter electrode sites on 500 μm centers with eight 15 μm wires interconnects. On the opposite surface lies a 200 μm SU-8 embedded fluidic channel. The fluidic channel was constructed by utilizing two wavelengths of ultraviolet light: a higher wavelength (>365 nm) that penetrates the SU-8 completely to construct the fluidic channel walls and a lower wavelength (

A capacitive surface-micromachined sensor suitable for the measurement of liquid and gas pressures was fabricated. The structure consists of a polysilicon stationary electrode suspended 0.7 /spl mu/m above a 20-/spl mu/m-thick lightly doped silicon diaphragm formed by a patterned etch stop. The a priori patterning of the buried etch stop yields diaphragm widths independent of wafer thickness variations with excellent alignment. The design described here has a pressure range of 100 PSI, a nominal capacitance of 3.5 pF with a full scale span of 0.8 pF, and a temperature coefficient of 100 ppm/spl deg/C/sup -1/. Each device, including a matched reference capacitor, occupies 2.9 mm/sup 2/, yielding approximately 2000 devices per 100-mm wafer.

Microelectromechanical systems (MEMS) have great potential for use in gastrointestinal (GI) imaging. Ultrasound and magnetic resonant imaging can provide useful information about the GI tract, but only optical coherence tomography (OCT) delivered endoscopically can be used to perform an optical biopsy of the GI tissue. In monitoring a condition such as Barrett’s esophagus, which typically requires regular random biopsies, the ability to achieve an optical biopsy is indispensible. While the existing method for obtaining an optical biopsy of the GI tract tissue produces functional images, there are drawbacks that could be improved upon. The gear-and-shaft assembly used to couple force from the motor at the proximal end to the distal imaging end requires a complex design [1]. By introducing a rotational MEMS device into the distal imaging end, a rotating optical coupling joint is no longer required at the proximal end, there is no need to precisely align the fixed fiber with the rotational drive shaft, and the metallic reinforcement sleeve can be eliminated leaving a simpler, more flexible delivery method [2]. In order to produce 3D OCT images, displacement in the z-direction needs to be coupled with rotation. A MEMS device that can achieve both vertical displacement and rotation further increases the simplicity of the device and decreases potential alignment and coupling errors. Our MEMS devices needs to be able to bend an OCT beam of light 90°, rotate that beam of light 360°, and simultaneously scan in the z-direction in order to produce 3D OCT images. Also, the device must fit inside the 1 mm diameter available in the endoscope. To accomplish this, we have designed, and are continuing to develop, a paraffin actuated micro mirror. The thermal expansion properties of paraffin wax have often been utilized in MEMS devices [3, 4]. We have made use of these properties in designing a piston like actuator. Heat is applied to a reservoir of paraffin enclosed by a parylene membrane. The paraffin expands and pushes the post above it upward with the developed force from its expansion. The amount of paraffin in each reservoir is controlled by the reservoir’s geometry and so by controlling the amount of heat applied, we can control how far the post above it moves in the vertical direction. Each device has three heaters, three reservoirs, and three posts. All three posts are attached to a single mirror. By appropriately cycling the applied heat to each reservoir, we expect to be able to move the mirror in a spiral like fashion. This will bend an applied beam of light 90° and rotate it 360° while achieving displacement in the z-direction.Copyright © 2009 by ASME

This paper mvestlgates the elcctrostatlc dnve and sense of polynhcon resonators parallel to the substrate, using an mterdlgtated capacitor (electrostatic comb) Three expenmental methods are used nucroscoplc observation mth contmuous or stroboscopic iummatlon, capacltlve sensing using an amphtude-modulation technique and SEM observation The mtnnslc quality factor of the phosphorus-doped low-pressure chemlcal-vapordeposited (LPCVD) polyslhcon resonators is 49 000 + 2000, whereas at atmosphenc pressure, Q < 100 The finger gap IS found to have a more pronounced effect on comb charactenstlcs than finger width or length, as expected from simple theory

This paper demonstrates the substrate dependency of the c-axis zinc oxide growth in radio-frequency sputtering system. Different deposition conditions were designed to study the influences of Si, SiO2/Si, Au/Ti/Si, and Au/Ti/SiO2/Si substrates on the piezoelectric and crystalline qualities of the ZnO thin films. Experimental results showed that the multilayer of Au/Ti/SiO2/Si-coated silicon substrate provided a surface that facilitated the growth of ZnO thin film with the most preferred crystalline orientation. The thermally grown amorphous silicon dioxide layer effectively masked the crystalline surface of the silicon substrate, thus allowing the depositions of high-quality titanium adhesion layer followed by gold thin film. The gold-coated surface allowed deposition of highly columnar ZnO polycrystalline structures. It was also demonstrated that by lowering the deposition rate at the start of sputtering, a fine ZnO seed layer could be created for subsequent higher-rate deposition. This two-step deposition method resulted in substantially enhanced ZnO film quality compared to single-step approach.

A capacitive surface micromachined sensor suitable for the measurement of liquid and gas pressures was fabricated. The structure consists of a polysilicon stationary electrode suspended 0.7 /spl mu/m above a 20 /spl mu/m-thick lightly-doped silicon diaphragm formed by a patterned etch stop. The a-priori patterning of the buried etch stop yields diaphragm widths independent of wafer thickness variations with excellent alignment. The design described here has a pressure range of 100 PSI, a nominal capacitance of 3.5 pF with a full scale span of 0.8 pF and a temperature coefficient of 100 ppm//spl deg/C. Each device, including a matched reference capacitor, occupies 2.9 mm/sup 2/ yielding approximately 2000 devices per 100 mm wafer.

We present the first microwave measurements of the dynamical impedance of an individual, electrically contacted single walled carbon nanotube. Both semiconducting and metallic nanotubes are measured. Using a semiconducting nanotube, we construct an LC nano-resonator at 2 GHz. The Q of the nano-resonator can be tuned by varying the back-gate voltage on the nanotube. In contrast, the Q of a resonator fabricated with a metallic nanotube is insensitive to the back-gate voltage. This represents the first step towards passive microwave signal processing components based on carbon nanotubes.

This paper presents the design, simulation, fabrication and testing of a piezo transduced high frequency micromechanical resonator. The resonator is designed to operate in the wine-glass mode and the anchors are optimized to both suppress spurious modes and minimize the energy loss into the substrate. The resonator is fabricated with a simple 4-mask low temperature process from SOI wafer. The highest temperature during the process is 250°C, allowing post-COMS integration compatibility. A prototype resonator with measured diameter of 100 µ m was tested in air using non-optimized experimental setup, with measured resonant peaks at 44.97 MHz and 138.5 MHz, which match the simulated result from Ansys©. The quality factor of 35 at 138.5 MHz is extracted, and is expected to be substantially higher if measured in vacuum with calibrated RF cables.

Two resonant micromechanical structures that have been designed, fabricated, and tested and which exhibited multiple modes of vibration are described. The first had a cantilevered inertial mass that was actuated by a curved-comb electrostatic drive attached near the root of the cantilever. The second structure had a straight-comb electrostatic-drive with a folded flexure suspension that was used to actuate the cantilevered inertial mass. The first structure exhibited two distinct vibration modes, and the second structure exhibited three distinct vibration modes. An analytic dynamic model has been developed and it predicted the vibrational mode shapes of the structures. Tests of the fabricated structures have demonstrated that peak-to-peak lateral displacements greater than 10 microns were feasible. Further, peak-to-peak angular displacements greater than 10 degrees have been measured during second mode vibration. The resonant frequencies of the structure varied from 1.7 to 33 kHz, depending on structure geometry. Cantilever structures with overhang lengths as great as 864 microns have been fabricated and operated with no perceptible contact between the inertial mass and the substrate. >

Space exploration in the coming century will emphasize cost effectiveness and highly focused mission objectives, which will result in frequent multiple missions that broaden the scope of space science and to validate new technologies on a timely basis. Micro electromechanical systems (MEMS) is one of the key enabling technologies to create cost-effective, ultra-miniaturized, robust, and functionally focused spacecraft for both robotic and human exploration programs. Examples of MEMS devices at various stages of development include microgyroscope, microseismometer, microhygrometer, quadrupole mass spectrometer, and micropropulsion engine. These devices, when proven successful, will serve as models for developing components and systems for new-millennium spacecraft.

Microelectromechanical systems (MEMS) are one of the three core enabling technologies within the Microsystems Technology Office (MTO) of the Defense Advanced Research Projects Agency (DARPA). Together with Photonics and Electronics, MEMS forms the foundation for a broad variety of advanced research projects sponsored by MTO. MEMS technology merges the functions of compute, communicate and power together with sense, actuate and control to change completely the way people and machines interact with the physical world. Using an ever-expanding set of fabrication processes and materials, MEMS will provide the advantages of small size, low-power, low-mass, low-cost and high-functionality to integrated electromechanical systems both on the micro as well as on the macro scales. Further, demands for increased performance, reliability, robustness, lifetime, maintainability and capability of military equipment of all kinds can be met by the integration of MEMS into macro devices and systems.

Space exploration in the coming century will emphasize cost effectiveness and highly focused mission objectives, which will result in frequent multiple missions that broaden the scope of space science and to validate new technologies on a timely basis. Micro Electro Mechanical Systems (MEMS) is one of the key enabling technology to create cost-effective, ultra-miniaturized, robust, and functionally focused spacecraft for both robotic and human exploration programs. Examples of MEMS devices at various stages of development include microgyroscope, microseismometer, microhygrometer, quadrupole mass spectrometer, and micropropulsion engine. These devices, when proven successful, will serve as models for developing components and systems for new-millennium spacecraft.

New design tools and automation strategies are neededto create robust, cost-effective, and manufacturable micro-machineddevices and systems. Some of the design automationissues include mixed-technology simulation, materialproperty prediction in the micron-size regime, self-consistencyin coupled electromechanical devices, integratedmodeling environment, micro-fluid modeling, and synthesisof device geometries and process flows. Advancement inthese areas will path the way to full-scale maturity of theMEMS field.

Microelectromechanical sensors, ADXL50 and XMMAS40G accelerometers which are fabricated with surface micromachining techniques are characterized for their total dose radiation response. Different failure mechanisms were observed when the sensor element or the whole device was irradiated.

This research was performed to address the issue of shock robustness in silicon microstructures. The improvements were incorporated by considering features to reduce stress concentration and by geometries that have a more uniform stress distribution. The design were evaluated by finite element models and by testing with wafer level techniques. The designs were intended to have the same fundamental frequency, inertia properties and damping properties. Six different designs were developed and distributed across 900 die on multiple 4-inch wafers. The wafers were subjected to repeated shocks at magnitudes of 130, 2008, and 3680 gs with a 0.25 msec duration. Automated optical inspection was used to interrogate each die and determine which test structures survived the shock test. Subsequent to testing, analysis of variance was used to identify the significant factors that influence the failure rate. This analysis has shown beam design, wafer orientation, acceleration level, and the interactions of beam design*wafer orientation, wafer orientation*acceleration level to be significant factors contributing to the failure rate. The designs were grouped according to mean failure rate. The `small bow tie' design had the highest failure rate and was a separate population. Its failure rate was two to four times that of other designs. The second grouping of lower failure rates included all designs to address the stress concentration. Of these designs, the `no gusset' design has the highest failure rate (twice that of other designs). The final grouping includes the gusset designs and the `medium' and `large bow tie' designs. The designs to improve stress distribution had the lowest mean failure rates of all designs.

The phased product development approach can be applied advantageously to develop and manufacture automotive microsensors. The phased approach involves a multifunctional team from innovation to development to eventual production and maintenance phases. The key advantage of this approach is the shortened development cycle and fast product introduction, while minimizing waste of resources and lowering risk of product failure. When applied to the product cycles of automotive sensors based on micromachining technology, this approach elucidates several critical considerations. In particular, since industrial application of micromachining technology is still at the infant stage, standards and design rules are not firmly established. Therefore, several important activities must be initiated simultaneously from the start of the innovation phase, which proves to be crucial to the prudent decision of technology alternatives and sensor system configuration. The use of a multifunctional team, as mandated in the phased approach, enables coherent development and optimization of the sense element, the fabrication technology, the packaging approach, the interface circuit configuration, and design features that allow efficient test and assembly flow. Also, with intermediate milestones within each phase, risk assessment and necessary midcourse adjustment to technology trade- offs can be both timely and accurate. Accelerometers, one of the most developed micromachined sensors, serve as representative examples that illustrate how the phased approach can benefits the commercialization of the newly established and rapidly expanding field of micromechanics.

The infusion of advanced technology into defense systems is accelerating, by necessity, to keep pace with the exponential growth in information accessibility. Critical to national security and global stability, military forces must sustain their technological edge over potential adversaries. It is obvious that such an advantage cannot be maintained by sole reliance on protecting access to high-tech information.

During the last decade, it was discovered that the mechanical properties and interactions of cells and their surrounding extra-cellular matrix play important roles in cellular activities. Substantial efforts have been made to develop various methodologies and tools to study cell mechanics. In this paper, we report an ongoing study on integrating the concept of a smart structure with a microfabricated thin film piezoelectric transducer for characterizing the various changes in mechanical properties associated with cellular events. A microbridge sensor integrated with a thin film piezoelectric transducer was created from silicon dioxide and zinc oxide sandwiched between two gold electrodes. The cells to be tested were cultured on the microbridge surface. The surface tractions exerted by the cells on the microbridge directly modulated the selected resonant behaviors, which were detected with the custom designed effective surface electrode. Our theory and simulation results showed, for the first time, that the application and changes in these surface tractions resulted in resonant and anti-resonant frequency shifts in the impedance response of the piezoelectric transducer. Both spatial and temporal information of dynamic cellular activities could be inferred from the changes in the impedance spectra. The design, theory, finite-element simulation, microfabrication techniques, and preliminary test results are discussed.

An experimental study of the levitation force, normal to the substrate, associated with interdigital capacitor electrostatic comb lateral actuators is reported. For compliant suspensions, normal displacements of over 2 mu m for a comb bias of 30 V were observed. This phenomenon is due to electrostatic repulsion by image charges mirrored in the ground plane beneath the suspended structure. By electrically isolating alternating drive-comb fingers and applying voltages of equal magnitude and opposite sign, levitation can be reduced by an order of magnitude while reducing the lateral drive force by less than a factor of two. >

This letter introduces a resonant mass sensor that is based on a lateral extensional mode piezoelectric resonator and has a minimum detectable mass of 10−15g at room temperature and atmospheric pressure. The resonator with size of about 200×50×1μm3 has a quality factor (Q) of >1400 at 60MHz, and as small as 0.1ppm shift of its resonant frequency can be detected. The 0.1ppm detection capability corresponds to a mass uncertainty of only about 4.6fg. We have experimentally demonstrated a minimum detectable frequency shift of ∼1.6ppm due to absorption of isopropanol vapor (73fg) on the sidewalls of the parylene-coated lateral extensional mode piezoelectric resonator.

This letter presents the design, fabrication, and testing results of a piezoelectrically transduced UHF micromechanical resonator. The resonator is designed to vibrate in the (2, i) in-plane mode, and thin-film zinc oxide is used for piezoelectric transduction. A four-mask process is developed to fabricate the resonator on silicon on insulator wafer, and the maximum processing temperature is kept below 250°C. Prototypes with various diameters are fabricated, with a measured resonant frequencies span from 44.97 MHz to 1.14 GHz. Quality factors around 200 are obtained on different devices. Motional impedance in the range of several hundred ohms is demonstrated.

This paper presents the design, simulation, fabrication, and test results of a new type of piezoelectrically transduced micromechanical disk resonator approaching UHF frequencies. The resonators were fabricated from silicon-on-insulator (SOI) wafers with a 4-mask low-temperature process. The highest processing temperature was 250/spl deg/C, allowing post-CMOS integration compatibility. Several prototype resonators with measured diameter of 100 /spl mu/m and 60 /spl mu/m were tested in air, with the highest resonant peak observed at 208 MHz, which matched well with simulation results from finite-element analysis. A quality factor of 15 at 208 MHz was extracted, and is expected to be significantly higher with an optimized design and vacuum testing.

Interdigitated finger (comb) structures are demonstrated to be effective for exciting electrostatically the resonance of polysilicon microstructures parallel to the plane of the substrate. Linear plates suspended by a folded-cantilever truss and torsional plates suspended by spiral and serpentine springs are fabricated from a 2 μm-thick phosphorus-doped low-pressure chemical-vapor-deposited (LPCVD) polysilicon film. Resonance is observed visually, with frequencies ranging from 18 kHz to 80 kHz and quality factors from 20 to 130. Simple beam theory is adequate for calculating the resonance frequencies, using a Young's modulus of 140 GPa and neglecting residual strain in the released structures.

We have designed a micro actuator system for precise transmission and reception of bio-optical signals. Our system consists of a first-in-kind polysilicon micro mirror held stationary at a 45/spl deg/ angle on top of a 360/spl deg/-rotating platform driven by a scratch drive array. The entire system is designed with a 1-mm diameter size constraint. This constraint allows the device to fit inside the tip of a catheter for use in biomedical endoscopy. We have developed two designs, based on a commercial micromachining process, to accomplish this. One mirror assembly is pulled into position at 45/spl deg/ while the other mirror assembly flips over itself into place. The benefit of the former mirror is that it can easily be coated with gold to improve reflectivity at the foundry. The benefit of the latter is that the optically-flat bottom surface of the polysilicon layer is used as the reflective surface of the mirror. Photoresist "hinges" are used to allow this system to self-assemble by surface tension induced through heating.

Proof-of-concept testing of a microfabricated vaporizing liquid thruster was performed. In this liquid-fed thruster concept, propellant vaporization is achieved in a microfabricated thin film heater arrangement. Chip temperatures of 100, 150 and 200 C were achieved at power levels of 3.5, 5.5 and 7.5 W. Voltage requirements were below 5 V for these temperature values. A substantial fraction of the heat was believed to have been conducted into the packaging material. Thermal characterization tests of chips placed onto insulating Pyrex blocks resulted in temperatures of about 90 and 150 C for power levels of 1.2 and 2.5 W, respectively, thus cutting thermal losses by more than half. One thruster chip was tested using water as a liquid propellant and vaporization was achieved at 7 W electric input power.

A systematic experimental study of viscous air damping in laterally moving planar microstructures is reported. Previous studies indicated that Couette and Stokes flow models underestimate microstructural damping. To investigate this discrepancy, a series of lateral resonant microstructures with different damping plates and combs was fabricated by polysilicon surface micromachining. The resonant frequencies and quality factors of the structures were measured electrically. By analyzing these data, the damping effects due to different geometries were elucidated and compared to theory. The results indicated that if edge and finite-size effects are included in the model, reasonably accurate predictions of the quality factors can be obtained even for small geometries and comb drives. An empirical formula that predicts the quality factor for a range of plate sizes and comb designs was derived. The damping effects as functions of structural thickness and structure-to-substrate separation are also reported.

The paper presents the design, simulation, fabrication, and preliminary test results of a novel micromechanical filter based on coupled piezoelectrically transduced resonators. This is the first report of two identical microfabricated free-free beam resonators coupled with two torsional beams forming a second-order mechanical filter. Piezoelectric transducers from thin-film ZnO were used to drive anti sense resonance, eliminating the need for precision fabrication of nanometer-scale gaps in contrast to electrostatic transduction. Fabrication was done with a four-mask process on SOI wafers with maximum temperature capped at 250/spl deg/C, allowing post-CMOS integration. Preliminary tests showed a resonant peak of 10.83 MHz and a quality factor of 41 under atmospheric pressure.