Rongshun Chen

A novel differential capacitive-sensing dual-axis accelerometer design using pendulum-proofmass, gimbal-springs, and harm vertical-combs

This study presents a novel dual-axis capacitive-type accelerometer design consists of a pendulum-proofmass (bulk Si), a gimbal-spring (poly-Si film), and vertical-combs sensing electrodes. This design has three merits, (1) pendulum-proofmass to produce torque by in-plane acceleration (offset-axis inertial force), (2) gimbal-springs enable the detection of dual-axis accelerations, and (3) high-aspect-ratio-micromachined (HARM) vertical-combs as the differential sensing electrodes to detect angular motion. In short, applying the HARM vertical-combs for differential capacitive sensing to detect the offset-axis inertial force is firstly implemented in this work. Measurement results show that sensitivities (non-linearity) of etch direction are 2.44mV/G (0.04%) of X-axis, and 51.99mV/G (0.11%) of Y-axis (measurement range: 0.05G∼2G). The resolution is 50mG for both axes. The cross-axis errors range from 0.005% to 11%.

Bistable criterion for mechanically bistable mechanism

Based on slope-deflection equations, we theoretically derived a determinant D as a criterion, in terms of structural and material properties, to determine if the bistability can occur for micro mechanically bistable mechanisms. When D <; 0, it will display bistable phenomenon if an appropriate force is applied to push the bistable mechanism; while D >; 0, bistable phenomenon cannot occur. The proposed bistable mechanisms have been successfully fabricated with different beam length and tilted angle. Experiments were conducted to validate the theoretical study for bistability. Comparing theoretical results with experimental ones, it showed theoretical solutions agree well with experimental results.

Monolithic integration of micro magnetic pillar array with anisotropic magneto-resistive (AMR) structure for out-of-plane magnetic field detection

A novel integrate micro magnetic pillar array with anisotropic magneto-resistive (AMR) structure for out-of-plane magnetic field detection has been proposed and demonstrated. The merits of this study are: (1) The magnetic pillar converts magnetic field from out-of-plane to in-plane and provide magnetic gain (G) where G≈1/N (N:demagnetization factor) [1]; (2) The micro magnetic pillar array can be batch fabricated and defined at appropriate locations, and further monolithically integrated with AMR sensor; and (3) The magnetic conversion efficiency can be easily further enhanced by increasing the density of magnetic pillar array. The AMR sensor with different magnetic pillar density has been implemented and measurements indicate that the AMR sensor with larger density of magnetic pillar array has better sensitivity and resolution for detecting out-of-plane magnetic field.

Implementation of polymer-dispersed liquid crystal microprism array for LED radiation pattern application

This study implements a novel lighting chip with tunable radiation pattern. The lighting chip consists of polymer-dispersed liquid crystal (PDLC) microprism array, LED, and Si-carrier. By integrating the characteristics of microprism and the scattering/transmitting modes of PDLC, the PDLC-microprism enables the tuning of radiation pattern when applying voltage. The lighting chip with PDLC-microprism has the following advantages, (1) no moving parts are required to tune the radiation pattern, (2) the shape of PDLC-microprism array can be easily changed by molding processes, and (3) the fabrication and packaging are performed at low temperature and the damage to PDLC is prevented.

The torque-enhancement design for magnetostatic scanner

This study presents two designs to enhance the magnetostatic torque to drive the scanner, (1) the lever arm, and (2) the ferromagnetic material pattern with higher length to width ratio.

Novel tunable optical modulation lens using magnetorheological effect

This study extends the fluid dispensing and sealing technology to realize a novel MR fluid lens (MR fluid: liquid polymer with magnetic particles) for light intensity modulation. Merits of the device: Optical transmittance of lens is controlled by (1) weight fraction of magnetic powder, and (2) orientation of columnar particles controlled by magnetic field. In applications, the MR fluid lens is realized on glass substrate and suspended MEMS structures. The light intensity modulation of MR fluid lens (diameter: 2000μm) by magnetic field is demonstrated. Measurements show the NdFeB liquid polymer (10wt%) has a 40% dark area change and 290% laser transmittance difference after applying magnetic field.

Lorentz force torsional actuator with embedded nickel structures

This study presents a Lorentz force torsional actuator design consisting of a Si-Ni compound frame. The proposed actuator design employs Si mold to simultaneously electroplate/pattern Ni, and the Ni and Si structures respectively provide electric routing and superior mechanical properties. As compare with the traditional design (Al wire routing on Si substrate), the thick Si-Ni compound structure could accommodate more turns and further increase the efficiency of Lorentz force at the same input current and device feature size. Moreover, the Si-Ni compound frame is nearly symmetric about the torsional axis, the proposed design reduces the wobble motion. The measurement results show that the wobble displacement of proposed design is only 52 nm as the optical scan angle is 20°. Comparing with the existing designs, the wobble displacement is decreased to 55% by the proposed design.

Magnetostatic torsional actuator with embedded nickel structures for pure rotation

This study demonstrates the magnetostatic torsional actuator consisting of a Si-Ni compound frame to significantly improve the driving force. The present design has three merits: (1) employ Si mold to simultaneously electroplate/pattern thick Ni, and the Ni and Si structures respectively provide magnetostatic force and superior mechanical properties, (2) the embedded Ni structures not only increase the ferromagnetic material volume but also enhance magnetization strength to enlarge magnetostatic torque, (3) the Si-Ni compound structure, which is nearly symmetric about the torsional axis, can decrease the moment of inertia and also reduce the wobble motion. Experiments show the Si-Ni compound scanner has optical scan angle θ=90°, and wobble motion and power consumption is significantly reduced.

Design and fabrication of CMOS-integrated thermoelectric IR microsensors

This work presents a thermoelectric infrared microsensor which is designed and fabricated with TSMC CMOS-MEMS processes. The proposed device can achieve the responsivity of 432.3 V/W and time constant of 2.49 ms at 1 atm.