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Microelectromechanical Systems, Journal of

Issue 5 • Date Oct. 2011

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Displaying Results 1 - 24 of 24
  • Table of contents

    Publication Year: 2011 , Page(s): C1 - C4
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  • Journal of Microelectromechanical Systems publication information

    Publication Year: 2011 , Page(s): C2
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  • Silica-Encapsulated Nanoparticle Films as Surface Modifications for MEMS

    Publication Year: 2011 , Page(s): 1065 - 1067
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (306 KB) |  | HTML iconHTML  

    In an effort to improve the reliability of microelectromechanical systems (MEMS), silica thin films deposited by chemical vapor deposition were used to encapsulate gold nanoparticle coatings. These composite coatings were shown to provide extremely durable films that significantly reduce the adhesion energy of silicon-based microcantilever beams. The results discussed suggest that encapsulating nanoparticle films with a durable silica thin film may lead to improved MEMS reliability. View full abstract»

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  • Quality Factor Enhancement of Lateral Microresonators in Liquid Media by Hydrophobic Coating

    Publication Year: 2011 , Page(s): 1068 - 1070
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB) |  | HTML iconHTML  

    In this letter, a new method of improving the quality factor of microresonators inside liquids is presented. By utilizing a conformally coated thin layer of parylene, which is highly hydrophobic, we trap air between the narrow gaps of a lateral resonator and prevent liquids from entering the gaps, thus preventing the viscous damping increase on the side surfaces. Initial tests with capacitive comb drives show that the quality factor decreases only threefold (from 157 to 55) when the device is operated in water after parylene coating. This method is very promising for in-liquid resonator applications, particularly real-time bioagent detection where high quality factor is essential for high mass resolution. View full abstract»

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  • Gamma Irradiation Effects on Surface-Micromachined Polysilicon Resonators

    Publication Year: 2011 , Page(s): 1071 - 1073
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (289 KB) |  | HTML iconHTML  

    The effects of gamma irradiation on the resonant frequency of a surface-micromachined polysilicon doubly clamped resonator are examined by a laser Doppler vibrometer. The resonant frequency of the resonator decreases by 2.1% for the 500-μm-long beam and 2.7% for the 300- μm-long beam after 32-krad (Si) gamma irradiation. The residual strains of the surface-micromachined polysilicon beams, which are estimated through the change of the resonant frequency, decrease by 2.7% and 5.4% for the 500- and 300-μm-long beams, respectively. Radiation effects of the polysilicon beams have been explained in terms of injection annealing. View full abstract»

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  • In Situ Tuning of Focused-Ion-Beam Defined Nanomechanical Resonators Using Joule Heating

    Publication Year: 2011 , Page(s): 1074 - 1080
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    Nanomechanical resonators have a huge potential for a variety of applications, including high-resolution mass sensing. In this paper, we demonstrate a novel rapid prototyping method for fabricating nanoelectromechanical systems using focused-ion-beam milling as well as in situ electromechanical characterization using a transmission electron microscope. Nanomechanical resonators were cut out of thin membrane chips, which have been prefabricated using standard cleanroom processing. We have demonstrated the fabrication of double-clamped beams with feature sizes down to 200 nm using a fabrication time of 30 min per device. Afterwards, the dynamic and structural properties of a double-clamped beam were measured after subsequent Joule heating events in order to ascertain the dependence of the internal structure on the Q-factor and resonant frequency of the device. It was observed that a change from amorphous to polycrystalline silicon structure significantly increased the resonant frequency as well as the Q-factor of the nanomechanical resonator. Aside from allowing detailed studies of the correlation between internal structure and nanomechanical behavior on an individual rather than a statistical basis, the combination of a short turnaround time and in situ nonlithographic tuning of the properties provide a flexible approach to the development and prototyping of nanomechanical devices. View full abstract»

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  • Postfabrication Electrical Trimming of Silicon Micromechanical Resonators via Joule Heating

    Publication Year: 2011 , Page(s): 1081 - 1088
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1307 KB) |  | HTML iconHTML  

    This paper presents a method to electrically trim the resonance frequency of a silicon bulk acoustic resonator (SiBAR) after its fabrication is completed. The small volume of the microresonator can be Joule heated to a sufficiently high temperature to allow for diffusion of deposited metals from its surface onto its bulk. Such high temperatures also facilitate the formation of silicon-metal bonds which, depending on the metal, are either stronger or weaker compared to the existing silicon-silicon bonds. The former leads to an overall increased stiffness of the resonating element thereby trimming up its resonance frequency, while the latter does the opposite. Both trimming-up and trimming-down by ~400 kHz have been demonstrated at a resonance frequency of 100 MHz (i.e., trimming range of 4000 ppm) using gold and aluminum, respectively. The possibility of increasing the trimming range to ~4 MHz (i.e., 40 000 ppm) by engineering the resonator geometry is also discussed and demonstrated. View full abstract»

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  • Microbricks for Three-Dimensional Reconfigurable Modular Microsystems

    Publication Year: 2011 , Page(s): 1089 - 1097
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (961 KB) |  | HTML iconHTML  

    This paper explores the design of “microbricks”-interlocking microscale building blocks that can be used to assemble and reconfigure 3-D structures on a regular lattice. We present the design and fabrication of a space-filling rotation and flip-invariant 500-μm microbrick architecture suitable for 3-D assembly. We describe the design considerations used to optimize mechanical, fabrication, and assembly properties of the components and the finished structures. The final brick geometry was fabricated using two different fabrication techniques: Silicon bricks were micromachined out of silicon, and SU-8 polymer tiles were built up in a three-layer process. The resulting bricks were characterized, and proof-of-concept structures comprising ten bricks were assembled to demonstrate the physical interlocking and compatibility between the two materials. We suggest that the presented interlocking geometry could serve in the future to fabricate passive and active modular macroscale structures from microscale components. View full abstract»

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  • Impedance-Based Force Transduction Within Fluid-Filled Parylene Microstructures

    Publication Year: 2011 , Page(s): 1098 - 1108
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (967 KB) |  | HTML iconHTML  

    We report on the use of electrochemical impedance (EI) as the basis for force transduction in Parylene-based microdevices. Electrolyte-filled microstructures were realized for extremely sensitive contact-force detection (10 mN range, ±0.023 mN resolution) enabled by EI-based transduction and are a promising platform for next-generation biomedical sensing technology. The design, fabrication, and characterization of Parylene-based electrochemical-MEMS (EC-MEMS) devices capable of microNewton contact-mode force measurement are presented and discussed. View full abstract»

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  • Development and Characterization of Multisite Three-Dimensional Microprobes for Deep Brain Stimulation and Recording

    Publication Year: 2011 , Page(s): 1109 - 1118
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    Novel 3-D multichannel microprobes are presented for deep brain stimulation and recording applications. The microprobes offer independent electrode sites around the shaft of the implant, providing the capability to control the profile of injected charge into the tissue. The devices are composed of planar flexible microprobes folded over cylindrical polyurethane shafts with diameters as small as 750 μm . A dramatic enhancement in the density/number of channels and a precise control over the dimensions of the electrode sites are achieved using this approach. The fabricated devices host 16 stimulating and 16 recording channels. The impedance characteristics and long-term behavior of electrodes were studied in acidic and saline solutions under prolonged pulse stress tests. To enhance the charge delivery capacity or reduce the impedances of the channels, iridium (Ir) was electroplated on gold electrode sites. Both Ir and gold channels demonstrate stable characteristics after pulse stress tests longer than 100 million cycles. The in vitro experiments in the whole hippocampus of a C57BL/6 mouse demonstrate the potential application of fabricated microprobes in simultaneous neural stimulation and recording. View full abstract»

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  • A Fully Passive Wireless Microsystem for Recording of Neuropotentials Using RF Backscattering Methods

    Publication Year: 2011 , Page(s): 1119 - 1130
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (929 KB) |  | HTML iconHTML  

    The ability to safely monitor neuropotentials is essential in establishing methods to study the brain. Current research focuses on the wireless telemetry aspect of implantable sensors in order to make these devices ubiquitous and safe. Chronic implants necessitate superior reliability and durability of the integrated electronics. The power consumption of implanted electronics must also be limited to within several milliwatts to microwatts to minimize heat trauma in the human body. In order to address these severe requirements, we developed an entirely passive and wireless microsystem for recording neuropotentials. An external interrogator supplies a fundamental microwave carrier to the microsystem. The microsystem comprises varactors that perform nonlinear mixing of neuropotential and fundamental carrier signals. The varactors generate third-order mixing products that are wirelessly backscattered to the external interrogator where the original neuropotential signals are recovered. Performance of the neurorecording microsystem was demonstrated by wireless recording of emulated and in vivo neuropotentials. The obtained results were wireless recovery of neuropotentials as low as approximately 500 microvolts peak-to-peak (μVpp) with a bandwidth of 10 Hz to 3 kHz (for emulated signals) and with 128 epoch signal averaging of repetitive signals (for in vivo signals). View full abstract»

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  • Piezoelectric MEMS Energy Harvester for Low-Frequency Vibrations With Wideband Operation Range and Steadily Increased Output Power

    Publication Year: 2011 , Page(s): 1131 - 1142
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1638 KB) |  | HTML iconHTML  

    A piezoelectric MEMS energy harvester (EH) with low resonant frequency and wide operation bandwidth was designed, microfabricated, and characterized. The MEMS piezoelectric energy harvesting cantilever consists of a silicon beam integrated with piezoelectric thin film (PZT) elements parallel-arranged on top and a silicon proof mass resulting in a low resonant frequency of 36 Hz. The whole chip was assembled onto a metal carrier with a limited spacer such that the operation frequency bandwidth can be widened to 17 Hz at the input acceleration of 1.0 g during frequency up-sweep. Load voltage and power generation for different numbers of PZT elements in series and in parallel connections were compared and discussed based on experimental and simulation results. Moreover, the EH device has a wideband and steadily increased power generation from 19.4 nW to 51.3 nW within the operation frequency bandwidth ranging from 30 Hz to 47 Hz at 1.0 g. Based on theoretical estimation, a potential output power of 0.53 μW could be harvested from low and irregular frequency vibrations by adjusting the PZT pattern and spacer thickness to achieve an optimal design. View full abstract»

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  • Dynamic Behavior of Liquid Microlenses Actuated Using Dielectric Force

    Publication Year: 2011 , Page(s): 1143 - 1149
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1137 KB) |  | HTML iconHTML  

    This paper presents a study of the dynamic responses of dielectric liquid microlenses via simulation and experiment. The dielectric force applied to the liquid microlenses was generated on the interface of two nonconductive isodensity liquids under ac biases. The dynamic responses of liquid microlenses of 0.5-10 mm in diameter were experimentally characterized; responses such as the dynamic contact angle and the response time with respect to viscosity, voltage, ac frequency, and droplet size were measured. The experimental results indicate that the viscosity and the droplet size are proportional to the response time. The applied ac frequency in the range of 1-50 kHz was inversely proportional to the response time. The contact angles in equilibrium were found to be inversely proportional to the ac frequency and the droplet size but nearly invariant to the viscosity. View full abstract»

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  • Active MEMS Valves for Flow Control in a High-Pressure Micro-Gas-Analyzer

    Publication Year: 2011 , Page(s): 1150 - 1162
    Cited by:  Patents (1)
    Multimedia
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    We present active electrostatic MEMS gas valves for Micro-Gas-Analyzer (MGA) flow control. These unique valves enable extremely low dead volume, highly integrated flow control chips for the MGA application, and potentially others (e.g., propulsion, pneumatic, and thermodynamic microsystems). We have demonstrated low leak rates ( <; 0.025 sccm, <; 0.0025 sccm on a similar passive valve design), high operating pressures 6.9×105 N/m2 (100 psig), a high-pressure record for valves of this size and type, and high flow rates (>; 25 sccm) using control voltages on the order of 100 V. The valve designs presented eliminate charge build-up issues associated with insulating materials and are closely tied to a base-lined microfabrication process (SUMMiT), allowing mass production. Using this process, which incorporates only CMOS compatible materials, eliminates outgassing and absorption problems inherent to microvalve designs that incorporate elastomers or organic bonding layers, and reduces contamination when the valve is part of the chemical analysis flowpath. The results obtained indicate that even higher performance level valves (>; 1.4 × 106 N/m2 or 200 psig operating pressure, at similar control voltage, flow rates, and leak rates) are possible. View full abstract»

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  • A Modular Heat-Shrink-Packaged Check Valve With High Pressure Shutoff

    Publication Year: 2011 , Page(s): 1163 - 1173
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    A novel check valve featuring adhesiveless packaging in heat-shrink tubing and dual regulation of in-plane flow is presented. The modular design enables simple replacement of valve components to modify valve behavior and performance. The specific design is intended for low-profile fluidic applications requiring flow control, such as drug delivery devices. The heat-shrink packaging scheme is extremely robust and can withstand >; 2000 mmHg (266.6 kPa) without leakage. Three different valve geometries were investigated and evaluated with theoretical and finite-element modeling analyses. Repeated flow regulation experiments on a fully packaged, hydrated valve demonstrated flow regulation between 25 and 2000 mmHg (3.33-266.6 kPa) and leak-free closure up to 500 mmHg (66.7 kPa) of reverse pressure with no observed stiction. The valve closing time constants were also determined. View full abstract»

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  • Reducing DRIE-Induced Trench Effects in SiC Pressure Sensors Using FEA Prediction

    Publication Year: 2011 , Page(s): 1174 - 1183
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    Burst force of several 4H-SiC pressure sensor diaphragms fabricated by reactive ion etching (RIE) is measured and coupled with finite-element (FE) analyses to extract a fracture strength of 786 ± 0.3 MPa. The result, which was in relative agreement with previously published values, was applied in various failure prediction models for RIE-induced trench defects that were responsible for the premature failures observed in SiC pressure sensors. The FE model associated with trench-free diaphragms was experimentally validated to prevent such failure, thereby resulting in the expansion of the sensor pressure handling capacity by more than twofold. The RIE fabrication process conditions for this model have been successfully implemented as a standard process. This result was extended further into developing failure prediction models for other observed RIE-induced etch characteristics. View full abstract»

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  • Modeling and Characterization of MicroPirani Vacuum Gauges Manufactured by a Low-Temperature Film Transfer Process

    Publication Year: 2011 , Page(s): 1184 - 1191
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (945 KB) |  | HTML iconHTML  

    The novelty of this paper is the proof of functional microdevice fabrication using a recently developed low-temperature transfer process. The process is based on adhesion control of molded Ni microstructures on a donor wafer by using plasma-deposited fluorocarbon films. Low-temperature adhesive bonding of the microstructures on the target wafer using benzocyclobutene sealing enables mechanical tearing off from the donor wafer. Interest of this process for manufacturing microsensors is demonstrated here in the case of microbeams used as pressure sensors based on the Pirani principle. A simple analytical model is used to estimate the electrothermal behavior of the suspended microwires as a function of the ambient gas pressure. Estimations are compared to experimental measurements performed on Ni electroplated microwires of 550-1200-μm length, 10-μm width, and 0.7-7- μm thickness characterized into a vacuum chamber. These microsensors present a maximum of sensitivity in the range of 0.1-100 mbar, which is in line with standard performances of Pirani gauges. The presented results thus demonstrate the interest of a simple film transfer process for the elaboration of 3-D functional microstructures. View full abstract»

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  • Glass and Quartz Microscintillators for CMOS-Compatible Multispecies Radiation Detection

    Publication Year: 2011 , Page(s): 1192 - 1200
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    This paper reports on a small-scale radiation detector that is sensitive to alpha, beta, gamma, and neutron radiation using scintillators doped with boron nanoparticles utilizing CMOS fabrication techniques. Two types of microscintillators have been fabricated and tested: One relies on sintered glass frit doped with boron nanoparticles, and the other uses quartz with boron diffused into the substrate. Radiation impinging on the scintillation matrix produces varying optical pulses of varying intensities depending on the type of radiation particle. The optical pulses are differentiated by on-chip pulse height spectroscopy and recorded on a microcontroller. The pulse height circuitry has been fabricated with both discrete circuits and designed into a single integrated circuit package. The quartz substrates have shown to be more transparent to the wavelength of the created optical pulses, which results in a higher count rate when compared to the tested glass scintillator. The quartz scintillator also shows better absorption of radiation particles, resulting in better detection efficiencies than the glass. The quartz also has been tested with varying doping levels and has the ability to detect neutrons. Source differentiation between 137Cs and 60Co has also been demonstrated. View full abstract»

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  • Multistage Planar Thermoelectric Microcoolers

    Publication Year: 2011 , Page(s): 1201 - 1210
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (658 KB) |  | HTML iconHTML  

    Many types of microsystems and microelectromechanical systems (MEMS) devices exhibit improved performance characteristics when operated below room temperature. However, designers rarely pair such devices with integrated cooling solutions because they add complexity to the system and often have power consumption which far exceeds that of the microsystem itself. We report the design, fabrication, and testing of both one- and six-stage thermoelectric (TE) microcoolers that target MEMS applications through optimization for low-power operation. Both coolers use thin-film Bi2Te3 and Sb2Te3 as the n-and p-type TE materials, respectively, and operate in a planar configuration. The six-stage cooler has demonstrated a ΔT = 22.3 °C at a power consumption of 24.8 mW, while the one-stage cooler has demonstrated a ΔT = 17.9 °C at a lower power consumption of 12.4 mW. View full abstract»

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  • A Ku-band Dual-SPDT RF-MEMS Switch by Double-Side SOI Bulk Micromachining

    Publication Year: 2011 , Page(s): 1211 - 1221
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1626 KB) |  | HTML iconHTML  

    This paper presents the design, fabrication method, and measurement results of a low-loss ohmic-contact radio-frequency microelectromechanical systems (MEMS) switch. A novel bidirectional electrostatic actuation mechanism has been developed for a dual single-pole double-throw switch that could be used for an X-Ku-band low-temperature cofired ceramic switched-line-type phase shifter. A high-aspect-ratio deep reactive-ion etching process and a thick gold-plating process were used to develop low-insertion-loss air-suspended MEMS waveguides and low resistive ohmic contacts. A typical insertion loss of 0.56 dB, a return loss of 19.4 dB, and an isolation of 51.4 dB were obtained at a Ku-band frequency of 12 GHz. View full abstract»

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  • 2011 IEEE International Electron Devices Meeting (IEDM)

    Publication Year: 2011 , Page(s): 1222
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    Freely Available from IEEE
  • ISPSD12

    Publication Year: 2011 , Page(s): 1223
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    Freely Available from IEEE
  • 2012 IEEE International Reliability Physics Symposium (IRPS)

    Publication Year: 2011 , Page(s): 1224
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    Freely Available from IEEE
  • Solid-state Sensor, Actuator and Microsystems Workshop

    Publication Year: 2011 , Page(s): C3
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    Freely Available from IEEE

Aims & Scope

The topics of interest include, but are not limited to: devices ranging in size from microns to millimeters, IC-compatible fabrication techniques, other fabrication techniques, measurement of micro phenomena, theoretical results, new materials and designs, micro actuators, micro robots, micro batteries, bearings, wear, reliability, electrical interconnections, micro telemanipulation, and standards appropriate to MEMS. Application examples and application oriented devices in fluidics, optics, bio-medical engineering, etc., are also of central interest.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Christofer Hierold
ETH Zürich, Micro and Nanosystems