Seal whiskers have been well studied in view of their remarkable hydrodynamic trail tracking capability. The considerable variation in the whisker lengths indicates that the whiskers have different natural frequencies sensitive to various frequency bands of hydrodynamic stimuli. However, a thorough experimental investigation of the natural frequencies of seal whiskers has not been conducted before. Here, we develop a novel and low-cost methodology for easy measurements of the natural frequencies of seal whiskers using a 3D-printed MEMS cantilever sensor featuring a graphene nanoplatelet piezoresistor and a soft encapsulation of the whisker base at the distal end of the cantilever.
We demonstrate a pressure-sensing approach based on the resonant operation of a single-crystal Si cantilever positioned near a flexible, pressurized membrane. The membrane deflection perturbs the electrostatic force acting on the cantilever and consequently alters the beam's resonant frequency. Sensitivity was enhanced by tailoring the actuating force nonlinearities through fringing electrostatic fields. With our coupled micromechanical system, we achieved frequency sensitivity to pressure and displacement of ≈ 30 Hz/kPa and −4 Hz/nm, respectively. Our results indicate that the suggested approach may have applications not only for pressure measurements, but also in a broad range of microelectromechanical resonant inertial, force, mass and bio sensors.
This paper presents a low-complexity and low temperature (85°C) fabrication process for vibration energy harvesters. The process employs lamination steps to transfer thinned PZT thick sheets onto flexible polymeric substrates, using dry film photoresist. The influence of geometrical parameters on the device performance were assessed by FEM simulations (using COMSOL) and supported by experiments. Optimization of the output power was performed by modifying the neutral plane within the device and by using a localized seismic mass at the tip, which has resulted in an output power of 30 μW at 52 Hz and an acceleration of 1g. Finally, a low-complexity and fully polymeric package is proposed, which together with the harvester process are compatible with large area fabrication methods.
This work reports a preliminary study of a fully implantable biomimetic accommodative intraocular lens (IOL) structured as a MEMS-valved endocapsular balloon. The biomimetic accommodative IOL is modeled after the geometry of a 29-year-old human lens and fabricated using only biocompatible materials. Successful accommodation, or focusing ability of the lens, is demonstrated in an objective benchtop test bed with enucleated porcine eyes. After surgical implantation of the lens, the focusing muscles of the eye are stretched in a manner consistent with prior work to demonstrate a change in focal power as the muscle is stretched in a manner similar to the natural lens. This work also includes detailed surgical procedures for the insertion and inflation of the lens.
For the first time, we present a simple process to fabricate a thin (>;5Lim), mechanically flexible, optically transparent, porous mono-crystalline silicon substrate. Relying only on reactive ion etching steps, we are able to controllably peel off a thin layer of the original substrate. This scheme is cost favorable as it uses a low-cost silicon <;100>; wafer and furthermore it has the potential for recycling the remaining part of the wafer that otherwise would be lost and wasted during conventional back-grinding process. Due to its porosity, it shows see-through transparency and potential for flexible membrane applications, neural probing and such. Our process can offer flexible, transparent silicon from post high-thermal budget processed device wafer to retain the high performance electronics on flexible substrates.
We report on the microfabrication and packaging of Cs-vapor cells filled with Ne or Ar for micro atomic clocks (MACs) based on the coherent population trapping (CPT). We present a two-step anodic bonding process to control the cell atmosphere for long-term operation of MACs. Furthermore, the results of thermal analysis of a cell embedded in the physical package are shown in order to discuss the optimal design of the package for the thermal management of the MAC.
This paper reports on a method for estimating direction of a sound with one directional acoustic sensor. Inspired by the two input structure of bushcricket ear, our sensor was designed to have an acoustic channel and a micro piezo-resistive cantilever. The radiated sound acts simultaneously on the external and on the inner surface of the cantilever. As the result, the directionality of our sensor varies with the frequency of incident sound. The sound direction was estimated by using directional responses of the sensor at multiple frequencies so that it does not require either angle scanning or microphone arrays. We demonstrated that this method enables the sound direction to be estimated with the average error of 4 degrees in laboratory experiments.
This paper presents a new low-cost, CMOS-compatible and robust wafer-level encapsulation technique developed using a stress-optimised PECVD SiC as the capping and sealing material, imparting harsh environment capability. This technique has been applied for the fabrication and encapsulation of a wide variety of surface- and thin-SOI microstructures that included microcavities, RF switches and various accelerometers. Advantages of our technique are its versatility, smaller footprint, reduced chip thickness and process complexity, post-CMOS batch processing capability and added functionality due to the possibility of integrating additional electrodes for MEMS. Besides fabrication details, this work also discusses related design aspects for large-area MEMS and demonstrates the encapsulation results. Successfully encapsulation of device geometries as large as 955times827 mum 2 has been achieved.
This paper addresses the key drivers of the "MEMS Epiphany," i.e. the successful interplay between the Technology Push and Design-Driven innovation strategies for MEMS (Micro-Electromechanical Systems) success in the consumer market. Before 2005, MEMS were known only by technology experts and were not yet ready for the high-volume consumer market. Only the marriage of a technological breakthrough in the MEMS world, pioneered by STMicroelectronics, and the creation and delivery of new applications for end users, driven by Nintendo and Apple, paved the way for the MEMS Epiphanies. This paper will focus on the technological challenges that STMicroelectronics faced to enable this historical landmark in the "MEMS Consumerization" era. And it will also discuss briefly the next possible MEMS Epiphanies in relation to new products and applications.
A fully-microfabricated wafer-level vacuum package of a micro fuel reformer was designed, fabricated and tested. For thermal insulation, a high-temperature reactor is suspended by microfabricated tubes, in which fuel and reformed gas flow, and is vacuum-packaged by anodic bonding. Conductive heat loss through air in the package was investigated by making the packaging pressure as a parameter. The measured heat loss is 1.2 W at a reforming temperature of 240degC, showing a potential to realize a micro fuel reformer with a thermal efficiency of 75%. Also, the temperature of the package outside is as low as 60degC, which is enough to install the micro fuel reformer in portable electronics.
We developed a novel technique to investigate local pH distribution on a chip using patterned hydrogel film made of UV photosensitive resin. The hydrogel is first patterned by photolithography in any shape on a glass, and later functionalized with the pH indicator, for example, bromocresol green (BCG). The hydrogel is polymerized by UV-ray illumination (300-400 nm) on the glass substrate, which is spin coated with the water-soluble prepolymer solution, and immobilized on the glass surface. Unexposed part can be removed easily by water. The hydrogel is hydrophilic, transparent, biocompatible, and is impregnated with the BCG. Then, the polydimethylsiloxane (PDMS) microchannel is assembled and bonded on the functionalized surface. In this way, we can make patterned pH sensitive surface in the microchannel. Local pH is measured from the color of the hydrogel impregnated with BCG based on the calibrated color information in YCrCb color space. We succeeded in measuring local pH distribution in the microchip.
This paper reports on a tensile-mode fatigue test in a constant humidity, even in a very high humidity, to reveal the mechanism of fatigue fractures of MEMS materials. A newly developed tensile-mode fatigue tester using the electrostatic grip can control the humidity from 25% RH to 90% RH. Using this tester, the fatigue life and strength of single crystal silicon (SCS) thin films and their dependence on the humidity were evaluated. In addition, using the statistical analysis for the fatigue test results, the fatigue parameter of SCS was obtained. The scale parameter, Weibull modulus, and fatigue parameter in the high humidity (85-90% RH) were 2.9times109 Pa, 13.6, and 86.3, respectively. With these parameters, the fatigue life prediction of SCS was performed for the long-term reliability assessment of MEMS devices.
This paper describes a concept, fabrication and evaluation of a novel nano-meter scale scanning thermal microscopy (SThM) system. The purpose of this research is a realization of a non contact type SThM system. A measurement probe in our system consists of a pyroelectoric detector and an infrared ray shielding film with an aperture for high lateral resolution. It is shown that the first results of the pyroelectric detector (PZT) and the shielding film with an aperture were successfully fabricated.
This paper proposes a novel MEMS tunable optical filter (TOF) using an auto-cloned photonic crystal (PhC). The auto-cloning method has great gains to fabricate multi-dimensional PhCs in productivity, flexibility and robustness. A two-dimensional PhC was fabricated by stacking Nb2O5and SiO2layers alternately keeping nano-scale periodic corrugations (190nm in pitch) formed on a substrate. This PhC was designed for splitting an incident light into the TM and TE modes at 500nm. Photonic band-gaps were changed by rotating the PhC and the transmittance of the TE mode was changed drastically at 420nm. The PhC was attached on the MEMS device (Eco Scan: Japan Signal) to control its angle of incidence. A resonance frequency of the MEMS structure was 183Hz and that rotation angle reached up to 40 degree. Switching characteristics of our MEMS-TOF were confirmed and its availability was demonstrated.
