Microelectromechanical systems (MEMS) are exposed to a variety of liquid environments in applications such as chemical and biological sensors and microfluidic devices. Environmental interactions between liquids and microscale structures can lead to unpredictable performance of MEMS in liquid environments. In this paper, the mechanical performance of microcantilevers in liquid environments was investigated through a series of experiments: Microcantilever beams were placed in a liquid-filled enclosure and cyclically actuated for ∼ 108 cycles. Silicon, silicon with titanium coating, silicon with a polymeric coating (SU-8), and silicon nitride microcantilevers were evaluated in deionized water, saline, and glucose. Microcantilever materials, liquid environments, and load levels (0-5 ± 0.5 MPa) were selected to be representative of sensor applications. The mechanical performance of the microcantilevers was evaluated by periodically monitoring changes in resonant frequency. All specimens performed reliably in air. Significant changes in resonant frequency, often exceeding 1%, were observed for uncoated silicon and titanium-coated microcantilevers immersed in saline and for SU-8-coated microcantilevers immersed in water. The changes in resonant frequency were attributed to mineral deposition for uncoated silicon microcantilevers in saline, corrosion fatigue for titanium-coated silicon microcantilevers in saline, and water absorption for SU-8-coated microcantilevers in water.
Bibliographical noteFunding Information:
Manuscript received June 8, 2010; revised October 1, 2010; accepted October 14, 2010. Date of publication February 10, 2011; date of current version April 1, 2011. This work was supported in part by the National Science Foundation under Award Number CMS-0300125. Subject Editor R. Maboudian.
Dr. Mantell is a member of the American Society of Mechanical Engineers (ASME). She was a recipient of the National Science Foundation Young Investigator Award, the ASME Young Engineer of the Year Award, and the George Taylor Award for teaching.
- microelectromechanical systems (MEMS) reliability