Lung-Jieh Yang

The marching velocity of the capillary meniscus in a microchannel

In this paper we describe an experimental method and an analytical model for characterizing the surface energy inside a microchannel of micrometer size by measuring the marching velocity or position of a capillary meniscus. This method is based on the fact that the force summation of the meniscus surface tension and the filling reservoir gravitation might produce a pressure to pull liquid into the channel, and the marching velocity or the instantaneous position of the meniscus is related to the surface energy. Both parylene and silicon-nitride microchannels with different surface conditions were fabricated to perform the fill-in experiments subject to different liquids. It is shown that our model agrees well with the experimental data and is a valid method.

Photo-patternable gelatin as protection layers in low-temperature surface micromachinings

This paper describes a newly developed low temperature photo-patternable gelatin technology that is useful to produce a thick (>10 μm) gelatin protecting and strengthening layer for weak MEMS microstructures. Example demonstrated here is the gelatin process integrated with the parylene MEMS technology. The complete processing details and formulae are reported and allow anyone to use gelatin like photo-resist. We find that it is a chemical-resistant and mechanical-robust material for MEMS applications.

CMOS microelectromechanical bandpass filters

This work fabricates a laminated-suspension microelectromechanical filter, respectively, by a fully compatible CMOS 0.6 μm single poly triple metal (SPTM) process and CMOS 0.35 μm single poly quadri-metal (SPQM) process. Experimentally, due to the top metal layer being used as the etch-resistant mask during the subsequent dry etching. Therefore, this study performs maskless etching with plasma and obtains excellent results including high selectivity and full release of the structure. Additionally, the microelectromechanical filter can be driven by applying low-voltage of around 5 V and a measured center frequency of around 13.1 kHz and a quality factor of around 1871 were obtained for a single-comb resonator operated in air. The filter successful proposed herein has a monolithic integration capability with the relative electric circuits in the standard CMOS 0.35 μm process.

Phase synchronization of micro-mirror arrays using elastic linkages

This paper investigates phase synchronization and concordant resonance of micro-mirror arrays and describes in detail a proposed design for a segmented micro-mirror with elastic linkages. The device replaces a conventional large area mirror, thus increasing the working frequency and allowing micro-mirror arrays to induce smaller vibration amplitude. The torsional micro-mirror array is fabricated using three conventional masks based on silicon bulk-micromachining technology. Experimental results of the prototype sample show that the phase difference among the mirror segments of the mirror array is below 1/15 cycle.

Photo-patternable gelatin as protection layers in surface micromachinings

This paper describes a newly developed low-temperature photo-patternable Gelatin technology that is useful to produce a thick (greater than 10 microns) Gelatin protecting and strengthening layer for weak MEMS micro-structures. Example demonstrated here is the Gelatin process integrated with the Parylene MEMS technology. What is reported here is the complete processing details and formulae that allow anyone to use Gelatin like photo-resist. We find that it is a chemical-resistant and mechanical-robust material for MEMS applications.

Fabrication Process of Integrated Multi-Analyte Biochip System for Implantable Application

This paper presents the integration of the fabrication processes for an implantable multi-analyte biochip system. The implantable biochip system has a microfluidic channel in which an electrochemical biosensor and a dielectrophoresis (DEP) micropump are fabricated by surface micromachining. The enzyme-based biosensor consists of three electrodes and detects the glucose level instantaneously by utilizing glucose oxidase (GOD). The DEP force resulting from the four-phase voltage exchange of the interdigitated electrodes drives the blood flow in the microchannel. By utilizing the MEMS fabrication and the electric circuit design, a compact implantable biochip system is achieved.

On gas permeation in PDMS

A theoretical model of gas permeation in polydimethylsiloxane (PDMS) is conducted for two prior works involving MEMS sensors and actuators. The issue for modeling a sensor is about using PDMS slabs to replace Pyrex glass as the packaging substrate for bulk-micromachined pressure sensors. The leakage pressure due to gas permeation in PDMS reveals the time-varying behavior of exponential decay. The issue for modeling an actuator is the flow rate in a PDMS-based gas permeation pump. The nonlinear dependence of the flow rate with the diffusion area can be explained by this model. The prediction of this theoretical result is therefore in qualitative agreement with two previous experimental data sets by a conventional curve-fitting technique.

Micro Pressure Sensors of 50μM Size Fabricated by a Standard CMOS Foundry and a Novel Post Process

This paper describes a piezoresistive micro pressure sensor with a size of 50μm made by a standard CMOS foundry and a novel post process. The material of the sensor diaphragm is silicon dioxide, and the piezoresistors are made by polysilicon. For releasing the diaphragms of the micro pressure sensors, this work proposes to use the front-side etching technique with etching holes of 5μm×5μm only. Finally, we use one of the protein stuffs, gelatin, to seal the etching holes. The sensitivity of the piezoresistive pressure sensor is 8.56±0.13 mV/V/psi.

The minimum time estimation for initiating tumor-cell attachment

This work presents the first part of a new framework for preventing the tumor-cell of carcinoma in situ transition from one organ to others. Using an ECIS (electric cell-substrate impedance sensing) chip coated with glutaraldehyde (GA)-crosslinked gelatin patterns suitable for cell attachment, the authors monitor the cell adhesion situation not only by optical microscope but also by electrical means. Therefore the authors design an experiment and a microfluidic chip for investigating the relationship between the metastasis and the surface morphology of blood vessels.

Buckled-type valves integrated by parylene micro-tubes

This paper demonstrates a newly developed parylene buckled-type valve with the same working principle of the buckled straw. Such a new design of valves uses the buckled region of plastic tubes as the on/off switch for flow control, and there is no need of adding deformable diaphragms or sealing parts into the valve device. By the merit of its concise mechanism, i.e., a straight pipeline with the region for buckling, the buckled-type valve intrinsically operates with almost zero dead volume. The fabrication sequence of this new valve combines the techniques of sacrificial mould of capillary glass tubes, conformal coating of parylene and SU-8 photolithography. A valve device of 1cm long, 0.8cm wide and with the buckled micro-tube of 350 /spl mu/m diameter is demonstrated. The turn-on angle of this valve verified as 135/spl deg/ experimentally.