Flexible MEMS skin technology for distributed fluidic sensing.

Abstract

Inherently, most MEMS devices are fabricated on rigid substrates. However, for a wide variety of applications, it has long been desirable that sensors, actuators, or circuits can be fabricated on flexible substrates so as to be mounted on nonplanar surfaces or even on flexible objects such as a human body. A novel flexible skin technology, which is compatible with MEMS and ICs processes, was developed in the Caltech Micromachining Lab for the distributed fluidic sensing. With this technology, a flexible shear-stress sensor skin was fabricated and successfully implemented on an Unmanned Aerial Vehicle (UAV). The flow separation detection along the leading edge of UAV was demonstrated in both wind tunnel and the real flight test. The complete UAV sensing/computing/controlling system, including microsensors, microelectronics, and microactuators, was also demonstrated in wind tunnel and ready for the flight test. This technology was further explored by making an underwater shear-stress sensor skin for applications such as flow pattern measurement of radio controlled submarines, and the study of the safety and arming mechanisms of next generation smart torpedoes. Underwater shear-stress sensor was developed, addressing the challenges of minimization of the pressure crosstalk and waterproof coating. A selective Parylene deposition method was investigated as well to achieve high shear-stress sensitivity and excellent waterproof simultaneously. With the skin structure, the packaging was significantly simplified and improved. Additionally, MEMS-IC integration is highly desirable since this integration promises to bring very important benefits such as operational improvement, packaging simplification, and cost reduction. For the first time, an IC-integrated flexible shearstress sensor skin, which has bias and signal conditioning circuitry on-chip, was developed by using post-CMOS MEMS processes. The fluidic sensing on a semicylindrical surface with the IC-integrated shearstress sensor skin was demonstrated in the wind tunnel. In addition to distributed fluidic sensing, the MEMS skin technology, with the demonstrated capability to be integrated with ICs, can enable many other important applications in biomedicine, wearable microsystems, RF systems, and robotics.