Seog-Soon Baek

A surface-micromachined tunable vibratory gyroscope

A tunable vibratory microgyroscope was fabricated by surface micromachining technology. The 7.5 /spl mu/m-thick polysilicon structural layer was deposited using LPCVD at 625/spl deg/C. The resonant frequency in the detection mode was higher than that in the driving mode so that gyroscope could be tuned to the resonant frequencies by applying the inter-plate DC bias. The gyroscope was driven in a resonant state by electrostatic force and detected the output due to a capacitance change between the plate and the polysilicon electrode. The resonant frequencies of gyroscope in the driving and detection direction were measured to be 10.48 kHz and 10.93 kHz, respectively. The resonant frequency in the detection direction could be shifted to 10.52 kHz by applying the tuning voltage of 4.0 V. The quality factor and resonant frequency of detection mode were significantly affected by ambient pressure and decreased as a function of ambient pressure. The noise equivalent rate of this device was about 0.1 deg/sec at 10/sup -2/Torr.

Investigation of reliability problems in thermal inkjet printhead

This paper presents a failure analysis result for enhancing the reliability of thermal inkjet printhead. A novel inkjet printhead is fabricated using MEMS process, and we analyze the failure mechanism of inkjet head based on detailed experimental observations. The design modification of micro heater to avoid an early stage of failure yields the reliability enhancement of printhead.

Failure mechanisms in thermal inkjet printhead analyzed by experiments and numerical simulation

This paper presents a failure analysis result for enhancing the reliability of thermal inkjet printhead. A novel inkjet printhead is fabricated using MEMS process, and we analyze the failure mechanism of inkjet head based on detailed experimental observations and numerical simulations. The failures presented in this work showed three primary factors influencing the failure modes and lifetime of printhead; bubble cavitation damage, thermal fatigue, and electromigration of heater. The design modification of micro heater to avoid an early stage of failure by electromigration yields the reliability enhancement of thermal inkjet printhead.

Visualization of bubbles generated by microheaters with various current density distributions

This work presents an experimental study to analyze the performance of thermal actuators to generate bubbles. The heaters are designed to have different current density distributions based on numerical analysis. The bubbles generated by heaters are compared to each other by visualization techniques. It is shown that the geometries and driving conditions of the heater strongly affect the bubble behaviors. The geometries like arc or trapezoid-shape induce nonuniform current densities and therefore change the driving conditions for generating bubbles. The experimental result reveals that the proper considerations on heater geometry are required to use the heater as a thermal actuator.