  We describe the design and construction of a new apparatus for detecting or
constraining deviations from Newtonian gravity at short length scales. The
apparatus consists of a new type of probe with rotary mass actuation and
cantilever-based force detection which is used to directly measure the force
between two micromachined masses separated by tens of microns. We present the
first data from the experiment, and discuss the prospects of more precisely
constraining or detecting non-Newtonian effects using this probe. Currently,
the sensitivity to attractive mass-dependent forces is equal to the best
existing limits at length scales near 5 microns. No non-Newtonian effects are
detected at that level.
