Gravitational Experiment Below 1 Millimeter and Comment on Shielded   Casimir Backgrounds for Experiments in the Micron Regime
  We present the status of an experimental test for gravitational strength forces below 1 mm. Our experiment uses small 1 kilohertz oscillators as test masses, with a stiff counducting shield between them to suppress backgrounds. At the present sensitivity of approximately 1000 times gravitational strength, we see no evidence for new forces with interaction ranges between 75 microns and 1 mm. While the Casimir background is not expected to be significant at this range, an extension of the shielding technique we employ may be useful for reducing this background in experiments below a few microns. We describe a possible implementation. 
Joshua C. Long, Allison B. Churnside, John C. Price