Wen-Pin Shih

Flexible Temperature Sensor Array Based on a Graphite-Polydimethylsiloxane Composite

This paper presents a novel method to fabricate temperature sensor arrays by dispensing a graphite-polydimethylsiloxane composite on flexible polyimide films. The fabricated temperature sensor array has 64 sensing cells in a 4 × 4 cm2 area. The sensor array can be used as humanoid artificial skin for sensation system of robots. Interdigitated copper electrodes were patterned on the flexible polyimide substrate for determining the resistivity change of the composites subjected to ambient temperature variations. Polydimethylsiloxane was used as the matrix. Composites of different graphite volume fractions for large dynamic range from 30 °C to 110 °C have been investigated. Our experiments showed that graphite powder provided the composite high temperature sensitivity. The fabricated temperature sensor array has been tested. The detected temperature contours are in good agreement with the shapes and magnitudes of different heat sources.

A low actuation voltage electrostatic actuator for RF MEMS switch applications

This paper presents the design, fabrication and characterization of an RF MEMS switch. Low actuation voltage and high isolation of the switch were achieved by exploiting buckling and bending effects induced by well-controlled residual stress. The effects of residual stress on improving the switch performance have been investigated using both analytical and numerical methods. The proposed RF switch has been fabricated by surface micromachining. The minimum actuation voltage of the fabricated switch was measured to be 10.2 V. At a 5 GHz signal frequency, the measured insertion loss and isolation are 0.21 dB and −44 dB, respectively. These results demonstrate that low voltage and high isolation of RF MEMS switches can be achieved with proper utilization of residual stresses.

A membrane actuator based on an ionic polymer network and carbon nanotubes: the synergy of ionic transport and mechanical properties

There is a growing interest in the development of ionic polymer?metal composites (IPMC) as sensors and actuators for biomedical applications due to their large deformation under low driving voltage. In this study, we employed poly(vinyl alcohol)/poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PVA/PAMPS) blend membranes as semi-interpenetrating polymer networks for ion exchange in IPMC construction. To improve the mechanical and electrical properties of the IPMC, multi-walled carbon nanotubes (MWNT) were added into PVA/PAMPS membranes. The actuator performance of the membranes was measured as a function of their water uptake, ion exchange capacity, ionic conductivity and the amount of MWNT in the membrane. The dispersion quality of the modified MWNT in the PVA/PAMPS membrane was measured using transmission electron microscopy. The cantilever-type IPMC actuator bends under applied voltage and its bending angle and the generative tip force were measured. Under an applied voltage, IPMC with ~1?wt% MWNT showed the largest deflection and generated the largest blocking tip force compared with those of IPMC with other various amounts of MWNT. These results show that a small addition of MWNT can optimize the actuation performance of IPMC. The result indicates that IPMC with MWNT shows potential for use as biomimetic artificial muscle.

Design and fabrication of an artificial skin using PI-copper films

This paper presents the design, fabrication and measurement of a flexible 8 times 8 temperature and tactile sensing array which will be used as the artificial skin for robot applications. The temperature and pressure sensing elements are heterogeneously integrated on a flexible copper-PI film using micromachining techniques. The tactile sensing elements are fabricated by dispensing conductive polymer on the pre-defined inter-digital copper electrodes. Discrete temperature sensor chips are employed as the temperature sensing elements. Scanning circuits are implemented and experimental results are also provided.

Design, Fabrication, and Application of Bio-Implantable Acoustic Power Transmission

Fully packaged acoustic power receivers are introduced. They can provide electronic energy to other implanted devices by receiving an external acoustic wave generated from the skin surface of the subcutaneous tissue. Piezoelectric ceramics make the internal devices of the receivers, and they are directly charged, converting pressure into an extractable electrical energy. Moreover, cohesive gel is used to package the internal devices, and the packages are biocompatible and sufficiently soft to absorb the incident wave that is generated at the skin surface. Additionally, the effects of the shape of the scattering package and ratio of the stiffness of the package to that of the tissue are considered in designing the receivers. The dominant frequencies and the energy efficiency of the receivers are measured in the very streaky pork, which is used to simulate human subcutaneous tissue. The results indicate that the spherical packaging is preferable to the cubic packaging when buried in the muscular layer. The maximum efficiency of the power transmission is found to be -48.2 dB, using the spherical package in the muscular layer of the streaky pork.

The fabrication of silicon-based PZT microstructures using an aerosol deposition method

This paper presents a series of processes for fabricating lead-zirconate-titanate (PZT) microstructures on a silicon substrate. An aerosol deposition method was used to deposit PZT thick film at room temperature. The low temperature deposition enabled a special lift-off process for patterning thick PZT films using a THB-151N photoresist. The milling rate of THB-151N by PZT particles was found to be the same as the PZT deposition rate of 5 μm h−1. Using this patterning technique, complex configurations of PZT microstructures have been demonstrated. Suspended multi-layer PZT microstructures have also been realized in this work.

3D face authentication by mutual coupled 3D and 2D feature extraction

In this paper, we present a novel method for automatic 3D face authentication. We introduce a coupled 2D and 3D feature-extraction method to determine the positions of eye sockets. The nose tip is considered as the extreme vertex along the normal directions of eye sockets. Once the nose tip and eye sockets are found, the bilateral symmetrical plane will be determined. The central profile which is on the bilateral symmetrical plane is the foundation for recognizing human face in our method. We use a weighting function for ICP according to the bilateral symmetrical behavior. We take 2.5D range image and its corresponding texture as the input data and compare the scanned model with the specified database model. The value of the weighted distance between two compared models is used for authentication. We have successively implemented this method for the authentication of the human faces. The result illustrates that this method work well in self authentication.

A Miniature System for Separating Aerosol Particles and Measuring Mass Concentrations

We designed and fabricated a new sensing system which consists of two virtual impactors and two quartz-crystal microbalance (QCM) sensors for measuring particle mass concentration and size distribution. The virtual impactors utilized different inertial forces of particles in air flow to classify different particle sizes. They were designed to classify particle diameter, d, into three different ranges: d < 2.28 μm, 2.28 μm ≤ d ≤ 3.20 μm, d > 3.20 μm. The QCM sensors were coated with a hydrogel, which was found to be a reliable adhesive for capturing aerosol particles. The QCM sensor coated with hydrogel was used to measure the mass loading of particles by utilizing its characteristic of resonant frequency shift. An integrated system has been demonstrated.

Electromechanical behavior of the curled cantilever beam

We propose an approximate analytical solution to the pull-in voltage of a microcurled cantilever beam. The analytical model considers the realistic situations, which include stress gradient, nonideal boundary conditions, and fringing field capacitance. The proposed analytical model can be used at wafer level for extracting the Youngs modulus of the thin film of which the cantilever beam is made. The approximate analytical solution is obtained based on the Eulers beam model and the minimum energy method. The accuracy of the proposed model is verified to be more accurate than the other published models. The model presented in this work can be used for wafer-level evaluation of the material properties through simple electrical testing and is also expected to find use in the design of microelectromechanical devices.

Fabrication and application of iron(iii)-oxide nanoparticle/polydimethylsiloxane composite cone in microfluidic channels

This paper presented the fabrication and applications of an iron(III)-oxide nanoparticle/polydimethylsiloxane (PDMS) cone as a component integrated in lab on a chip. The two main functions of this component were to capture magnetic microbeads in the microfluid and to mix two laminar fluids by generating disturbance. The iron(III)-oxide nanoparticle/PDMS cone was fabricated by automatic dispensing and magnetic shaping. Three consecutive cones of 300 µm in height were asymmetrically placed along a microchannel of 2 mm in width and 1.1 mm in height. Flow passing the cones was effectively redistributed for Renolds number lower than 3.45×10-3. Streptavidin-coated magnetic microbeads which were bound with biotin were successfully captured by the composite cones as inspected under fluorescence microscope. The process parameters for fabricating the composite cones were investigated. The fabricated cone in the microchannel could be applied in lab on a chip for bioassay in the future.