Hongshen Ma, James White, Joseph Paradiso, Alexander Slocum

Abstract

We have developed a sub-nanometer level displacement sensing system for a MEMS device called the Nanogate. The Nanogate is a tunable nanometer gap between ultra smooth surfaces of silicon and Pyrex. The separation between the surfaces can be as small as a few nanometers to as large as one micron. The Nanogate was created as a valve for precisely controlling very small gas and liquid flows, but it is also envisioned as a device where the variable gap can be used to filter particles and molecules by size. One advantage of our system is that the displacement measurement does not directly measure the capacitance of the nanometer gap hence does not depend on the dielectric properties of the material flowing in the gap. Our results show our capacitive sensor with a noise floor of 1.2Å RMS and long-term drift of 2.5nm.