Microbat
Nick Pornsin-Sirirak, Yu-Chong Tai
Collaborators: Hany Nassef (UCLA), Chih-Ming Ho (UCLA), Joel Grasmeyer (AeroVironment), Matt Keennon (AeroVironment)

Through the discovery of flapping-wing (unsteady-state) aerodynamics, the world's first electric-powered palm-sized ornithopter has been successfully developed and test-flown. This effort is enabled by the use of a new titanium-alloy MEMS (Micro-Electro-Mechanical Systems) airframe/wing technology to produce light but robust 3-D wings. Parylene-C is used as wing membrane. This new wing design results in a 40% wing area reduction compared to the 1st generation wing. We have built a system that includes a lightweight NiCd battery and an electrical motor, a gearbox transmission design of 22:1 gear ratio with 90% efficiency, and a DC-to-DC voltage converter. Together, it allows us to design a complete system with necessary components within the weight budget for a successful flight. So far, the best flight duration obtained by Microbat was 18 seconds. It is mainly limited by the power source. (full report)

Micromachined Fluidic Couplers
Ellis Meng, Shuyun Wu, and Yu-Chong Tai

Several types of silicon fluidic couplers have been designed, fabricated, and tested for the purpose of facilitating external connections to MEMS fluidic devices. By using both bulk micromachining and DRIE techniques, couplers of various geometries have been produced for use with any standard MEMS fluidic port. Furthermore, couplers exhibit excellent performance, having an operating range of at least 0-1300 psi. (full report)

Polymer Based Electrospray Chips for Mass Spectrometry
Xuan-Qi Wang, Amish Desai, and Yu-Chong Tai
Collaborators: Lawrence Licklider, Terry D. Lee (Beckman Research Institute, City of Hope Research Center, Duarte, CA)

We have developed a MEMS system with an overhanging polymer microcapillary 2.5 mm in length and with a 5 µm x 10 µm orifice size at the tip. The fabricated systems have been successfully interfaced with a mass spectrometer (MS) to validate electrospray ionization (ESI) for biochemical analysis. The prediction of a reduction in Taylor cone size has also been observed with real time ESI fluid visualization from our chip. Built-in micro particle filters and centimeter long serpentine microchannels were fabricated on the chip with a low temperature process by using the Parylene polymer as a structural material, aluminum and photoresist as sacrificial layers, and bromine triflouride (BrF3) gas phase etching for final microcapillary releasing. The use of an overhanging polymer structure adds a new a level of mechanical robustness that was never achievable with other thin films. Functionality of our device was proven by consistent detection of Myoglobin in a 200 nM solution at a flow rate of 35nL/min and a voltage potential of 1.5 kV. (full report)

MEMS Flow Sensors for Nano-Fluidic Applications
Shuyun Wu, Qiao Lin, Yin Yuen, and Yu-Chong Tai

We have developed micromachined thermal sensors for measuring liquid flow rates in the nanoliter-per-minute range. The sensors use a boron-doped polysilicon thin-film heater that is embedded in the silicon nitride wall of a microchannel. The boron doping is chosen to increase the heater's temperature coefficient of resistance within tolerable noise limits, and the microchannel is suspended from the substrate to improve thermal isolation. The sensors have demonstrated a flow rate resolution better than 1 nL/min, as well as the capability for detecting micro bubbles in the liquid. Heat transfer simulation has also been performed to explain the sensor operation and yielded good agreement with experimental data. (full report)

Micromachined Rubber O-ring Micro-Fluidic Couplers
Tze-Jung Yao, Yu-Chong Tai

The goal of this project is to develop a "quick-connect" for microfluidic devices. We have developed a simple silicone-rubber O-ring MEMS coupler. The MEMS O-ring couplers are easy to fabricate and use, reusable, can withstand high pressure (>60psi), and provide good seals. To demonstrate this concept, a quick-connect coupler between a glass capillary tube and a silicon chip has been fabricated and tested. More than 60 psi seal has been achieved between a glass tube (860 µm O.D.) and a rubber O-ring (400µm I.D.) without measurable leakage. (full report)

Super Manueverable UAV Controlled by M³ System
Fukang Jiang, Charles Grosjean, Yong Xu, Yu-Chong Tai
Collaborators: Chih-Ming Ho (MAE, UCLA), Ray Morgan, Martyn Cowley, Scott Newbert (AeroVironment Inc.)

An aircraft for the future - having no tail, controlled by M³ systems, and with no traditional control surfaces - will be developed for low altitude surveillance. A new robust system of distributed microsensors and microactuators, with associated microelectronics (a M³ system) will be designed and fabricated to satisfy flight test requirements. A new aircraft will be designed from scratch to accentuate the concept of achieving aerodynamic maneuvering through a micromachine-based deformable smart surface. This new aircraft design concept can significantly reduce weight, overall power consumption and radar cross-section. (full report)

Distributed Turbulent Flow Control by Neural-Networked MEMS
Zhigang Han, Qiao Lin, Xuan-Qi Wang, Fukang Jiang, Thomas Tsao, Yu-Chong Tai
Collaborators: Vincent Koosh (Caltech), Rodney Goodman (Caltech), James Lew (MAE, UCLA) , Chih-Ming Ho (MAE, UCLA)

The ultimate goal of this project is to develop fully integrated MEMS with microsensors, microactuators, and microelectronics (M³) for turbulent boundary layer control. We have developed many generations of MEMS shear-stress sensors for vortex detection. The latest one is a fully integrated shear-stress sensor using a post-IC process that is added onto foundry-processed CMOS wafers. This shear-stress sensor uses a gate-polysilicon hot-wire as the sensing element that sits on a freestanding Parylene diaphragm suspended over a cavity. A special Parylene vacuum sealing and etch back process is used to achieve better thermal isolation and overall sensitivity. Wind tunnel testing of this sensor shows a sensitivity of 30 mV/Pa and a measured bandwidth of 18 kHz. We have also performed extensive theoretical analysis of these sensors. The resulting 2D MEMS shear-stress sensor theory, which includes heat transfer effects ignored by the classical theory, is verified by experimental data. We also perform 3-D heat transfer simulation and the results agree with the testing data and support the proposed new theory. (full report)

Micromachined Gyroscope Using Operating Principles from the Fly's Halteres
Oliver Landolt, Zhigang Han, Christof Koch, Yu-Chong Tai

We are developing a surface micromachined 2D angular velocity sensor -- also known as gyroscope -- with the intention of minimizing power consumption. By using a detection principle inspired by the fly's haltere system, we expect our sensor to tolerate a higher noise level than previous designs for detecting the direction of the axis of rotation, thereby enabling a significant reduction of supply voltage and power consumption. Another feature is that the mechanical structure will be fabricated with a material called parylene using a novel technology developed in-house. The target application is flight control in extremely small air vehicles. (full report)