A one-chip microelectromechanical system (MEMS) fabrication process, termed as a short MEMS process, using a one-chip silicon-on-insulator (SOI) diaphragm is proposed in this study. First, an SOI-MEMS process characterized by maskless exposure was used to fabricate the SOI diaphragm. We subsequently modeled and fabricated an asymmetric micromirror using the proposed short MEMS process and the SOI diaphragm to evaluate the proposed approach. Resonance frequencies of 48 Hz and 14,840 Hz were obtained using a piezoelectric ceramic vibrating element. For a measured thickness of 11.89 µm and over-etched width of 3 µm, the scanning resonance frequencies were determined to be 52 and 15,614 Hz in the low-speed and high-speed mirror, respectively. The calculated values were in good agreement with the experimental results. This short MEMS process may be useful in fabricating a one-chip MEMS using a one-chip SOI diaphragm.
This paper describes development of self-heated stage suitable for thermal reactive ion etching (TRIE) of the functional metals. Thermal reactive ion etching was evaluated using both experiments and simulations for etching functional metals. The self-heated stage was designed based on the simulation results. TRIE employs a self-heated stage which is thermally insulated aluminum plate as the etching stage of a regular RIE apparatus. The stage temperature increases rapidly within 10 min and etch rate is not depend on process time. TRIE technique was used to etch various kinds of functional metals: Ti, Mo, Ta, Nb, and Ti alloy (Ti-6Al-4V). It did improve the etching rate of these materials greatly.
Online monitoring of infrastructures attracts great interests in recent years because of the increasing of nature disasters and the aging of bridges, high-ways, buildings, etc. In road infrastructure monitoring system (RIMS) project, to ensure enough long lifetime, i.e. > 10 years, and low maintenance cost of the sensor nodes when deployed to wild field environments for infrastructure monitoring, an all-in-one ceramic package with stand-alone power source and wireless communication is under developing without any external physical interconnections. This paper reports the development and evaluation of a wireless power transmission module for power backup and rescue when built-in solar cell or other power source cannot supply sufficient energy. The results clearly revealed that efficiency of the wireless power transmission, as high as 73.2%, was achieved when the thickness of the ceramic package was 3 mm. Thanks to the impedance matching circuit, a 100 F lithium-ion capacitor (LIC) can be fully-charged within a few minutes by using above module. Moreover, a hybrid RFID chip was introduced as a data-recorder for trouble shooting, which is technically important for practical applications of above all-in-one sensor nodes for infrastructure monitoring.
We have been studied the light addressable amperometric sensor (LAAS) that enables two dimensional chemical imaging. In this study we report a prototype of the LAAS microarray by attaching a well plate on the LAAS device. The LAAS microarray performs individual measurements by selecting each well using addressing light without discrete wirings.
In automotive and industrial fields, pressure sensors are a key component for precisely controlling the mechanical systems. Conventional MEMS-based pressure sensors have an advantage in noise resistance, because both strain gauges and control circuits are integrated in one chip. However, the MEMS-based pressure sensors are generally fabricated on an Si substrate, and have a low stability against various active gases. Thus, we have newly proposed a pressure sensor which consists of an Si-based strain sensor set on a stainless steel diaphragm with a high stability against the active gases. The key technology is that a Koval plate is inserted between the strain sensor and the stainless steel diaphragm, for preventing the breakage or the delamination of the strain sensor at the bonding interface due to a difference in thermal expansion. Structure of the sensor including the shape and the size of Koval plate and the assembly position of the strain sensor were designed using structural simulation and experiments. Eventually the 2.8-mm-wide and 0.17-mm-thick Koval beam was bridged on the stainless steel diaphragm for efficiently transmitting the diaphragm deformation to the strain sensor. The strain sensor was assembled at the edge of Koval beam with a glass bonding technique. Consequently, the developed pressure sensor has achieved a small dispersion of less than 1 %F. S. in a temperature range from 0 °C to 85 °C.
Novel miniaturized tactile devices, which provide a person with vibration stimulation, are proposed. The strategy is to hit the skin with a resonantly oscillating proof mass. The tactile devices consist of a Si proof mass and a beam formed by laminated thin-film PZT and polymer. The fabricated devices generated large displacement with high durability. Tactile experiments suggest that all examinees experienced vibration at displacement of 1.3 mm for a 4 mm × 4 mm device. For wearable monitoring systems of human activities, the energy consumption was estimated at 12 µW and the major energy loss was attributed to dielectric loss.