Ahra Lee

Barbed micro-spikes for micro-scale biopsy

Single-crystal silicon planar micro-spikes with protruding barbs are developed for micro-scale biopsy and the feasibility of using the micro-spike as a micro-scale biopsy tool is evaluated for the first time. The fabrication process utilizes a deep silicon etch to define the micro-spike outline, resulting in protruding barbs of various shapes. Shanks of the fabricated micro-spikes are 3 mm long, 100 ?m thick and 250 ?m wide. Barbs protruding from micro-spike shanks facilitate the biopsy procedure by tearing off and retaining samples from target tissues. Micro-spikes with barbs successfully extracted tissue samples from the small intestines of the anesthetized pig, whereas micro-spikes without barbs failed to obtain a biopsy sample. Parylene coating can be applied to improve the biocompatibility of the micro-spike without deteriorating the biopsy function of the micro-spike. In addition, to show that the biopsy with the micro-spike can be applied to tissue analysis, samples obtained by micro-spikes were examined using immunofluorescent staining. Nuclei and F-actin of cells which are extracted by the micro-spike from a transwell were clearly visualized by immunofluorescent staining.

Comparison between a moving bed bioreactor and a fixed bed bioreactor for biological phosphate removal and denitrification.

Moving bed bioreactors (MBBR) and fixed bed bioreactors (FBBR) were compared for biological phosphorus removal and denitrification. The sorption denitrification P-elimination (S-DN-P) process was selected for this study. Results indicated that all nutrients were removed by the FBBR process compared with the MBBR process: 19.8% (total COD), 35.5% (filtered COD), 27.6% (BOD(5)), 62.2% (acetate), 78.5% (PO(4)-P), and 54.2% (NO(3)-N) in MBBR; 49.7% (total COD), 54.0% (filtered COD), 63.2% (BOD(5)), 99.6% (acetate), 98.6% (PO(4)-P), and 75.9% (NO(3)-N) in FBBR. The phosphate uptake and NO(3)-N decomposition in the FBBR process during the denitrification phase were much higher than for the MBBR process despite being of shorter duration. Results obtained from this study are helpful in elucidating the practical implications of using MBBR and FBBR for the removal of bio-P and denitrification from wastewater.

The first sub-deg/hr bias stability, silicon-microfabricated gyroscope

The first sub-deg/hr bias stability gyroscope is fabricated in single crystal silicon using the SBM (sacrificial bulk micromachining) process. The quadrature error is a major concern in MEMS gyroscopes for high performance. To minimize the quadrature error, the fabricated gyroscope has a very flat bottom surface, which gives a highly symmetrical proof mass, and springs, which, in turn, provide high performance levels with significantly reduced quadrature error. The fabricated gyroscope has a bandwidth of 58 Hz, and 4-hr bias stability of 0.3 deg/hr.

A disposable MEMS-based micro-biopsy catheter for the minimally invasive tissue sampling

This paper presents a novel minimally invasive MEMS (micro-electromechanical system)-based micro-biopsy catheter for the diagnosis of gastrointestinal tissue samples. Conventional macro-scale biopsy tools such as biopsy forceps often cause a significant discomfort, infectious risk, and injury to the patients. In this study, a disposable micro-scale biopsy tool is proposed for the first time and MEMS technology is implemented for the fabrication process. Micro-biopsy catheter successfully extracts tissue samples from the small intestines of the anesthetized rabbit and pig. The proposed micro biopsy catheter is found to be useful in minimally invasive diagnosis.

Chip scale packaging with surface mountable solder ball terminals for microsensors

This paper presents a simple and low-cost flip chip bumping method with vertical feedthroughs for MEMS WLCSP. The vertical feedthroughs are fabricated on glass wafer using sand-blasting, and these provide inherent aligning jig for micro-ball arrangement. The experimental evaluations using MEMS accelerometer are also presented. The proposed method can be a more cost-effective solution by eliminating the conventional expensive and complex process including electroplating or ball-aligning jig. The feasibility of WLCSP is experimentally demonstrated by testing the developed devices.

A 37 ppm/°C Temperature Compensated CMOS ASIC with ±16 V Supply Protection for Capacitive Microaccelerometers

A high reliability CMOS-MEMS hybrid microaccelerometer system is presented. To enhance the temperature response and to minimize die-to-die variations, a low-noise continuous time front-end architecture with temperature compensation and parasitic cancellation is proposed. The temperature coefficients of the output bias and the scale factor are measured to be 37 ppm/degC and 27 ppm/degC, respectively. The bias instability level of the system is measured to be 42 mug. The integrated +16 V power supply protection block gives the enhanced system reliability and reduced form-factor.

Development of a MEMS-based Acceleration Sensing Module for Electronic Stability Program

This paper describes our development work for acceleration sensing modules for electronic stability program (ESP) systems. The MEMS-based accelerometer is fabricated using the unique sacrificial/bulk micromachining (SBM) process by us. The sensing module is designed to measure low level accelerations accurately and be stable in an automotive environment. This paper describes the accelerometer design and fabrication, electronic circuits and PCB design, module assembly, and performances of the developed sensing module. The developed sensing module offers analog voltage output with ±1.5g dynamic range, 0.05% non-linearity, 0.2mG resolution and l295㎷/g scale factor. The module includes a CAN2.0A interface and yields good experimental performances when implemented on a CAN test server.

Modeling and Simulation of the Microgyroscope Driving Loop using SPICE

A simulation model of vibratory capacitive microgyroscope and its driving loop is designed using SPICE. The vibratory microgyroscope is basically microelectromechanical system; therefore the simulation model should be expressed mechanical and electrical properties. To modelling the microgyroscope, the Analog Behavioral Model is used. In order to design a driving loop of vibratory microgyrosope, the the Barkhausen criteria is considered. The co-simulation of MEMS sensing element and its interface circuit is performed. The SPICE simulation model of the vibratory microgyrocope is designed, and the driving loop of the microgyroscope is simulated using the designed simulation model. The simulation results demonstrate the validity of the designed model and its interface circuit

Two-chip implemented, wafer-level hermetic packaged accelerometer for tactical and inertial applications

A two chip implemented, wafer-level hermetically packaged accelerometer is presented. The accelerometer core is fabricated using the SBM (sacrificial bulk micromachining) process. The fabricated accelerometer core accomplishes high performance, high yield and high reliability by the inherent high-aspect-ratio, footing-free advantages of the SBM process. In order to protect the accelerometer core from environmental changes, a wafer-level hermetic packaging process is performed by using glass-silicon anodic bonding. The capacitive detection circuit adopts an EEPROM trimmable architecture to reduce the die-to-die variations. The fabricated accelerometer has the noise equivalent acceleration resolution of 43 /spl mu/g, input range of /spl plusmn/10 g, Output nonlinearity of 0.1% FSO, scale factor of 130 mV/g, and 4-hr bias stability of 1.10 mg.

Estimation of angular velocity and acceleration by using 2 linear acceleration sensors

Abstract This paper presents a method to measure angular velocity with two silicon-based MEMS acceleration sensors which have the resolution of 0.08 mg. This paper proposes measurement results using the technique to compensate the alignment error and estimate an angular velocity with two acceleration sensors fabricated by sacrificial bulk micromachining (SBM) process. The technique also estimates an angular velocity of a commercial cleaning robot, which has been tried to make the unit cost of production lower, by using two acceleration sensors without using a gyroscope.