Battery-powered, wireless MEMS sensors for high-sensitivity chemical and biological sensing

Researchers at Oak Ridge National Laboratory (ORNL) are developing selectively coated cantilever arrays in a surface-micromachined MEMS process for very high sensitivities in chemical and biological sensing. Toward this end, we have developed a one-dimensional (1-D) 10-element microcantilever array that we have coated with gold for mercury sensing and palladium for hydrogen sensing. Ultimately we will coat each element with a different coating. Currently, measurements have been performed using a companion analog 1.2-/spl mu/m CMOS eight channel readout chip also designed at ORNL specifically for the microcantilever arrays. In addition, we have combined our sensors with an ORNL-developed RF-telemetry chip having on-chip spread spectrum encoding and modulation circuitry to improve the robustness and security of sensor data in typical interference- and multipath-impaired environments. We have also provided for a selection of distinct spreading codes to serve groups of sensors in a common environment by the application of code-division multiple-access techniques. Our initial system is configured for use in the 915-MHz Industrial, Scientific, and Medical (ISM) band. The entire package is powered by four AA batteries.