Search for Screened Interactions Associated with Dark Energy below the 100 μm Length Scale

We present the results of a search for unknown interactions that couple to mass between an optically levitated microsphere and a gold-coated silicon cantilever. The scale and geometry of the apparatus enable a search for new forces that appear at distances below 100 mu m and which would have evaded previous searches due to screening mechanisms. The data are consistent with electrostatic backgrounds and place upper limits on the strength of new interactions at < 0.1 fN in the geometry tested. For the specific example of a chameleon interaction with an inverse power law potential, these results exclude matter couplings beta > 5.6 x 10(4) in the region of parameter space where the self-coupling Lambda greater than or similar to 5 meV and the microspheres are not fully screened.