Testing Newtonian gravity at ultra-short distances

The appearance of new fundamental forces and extra-dimensional modifications to gravity in extensions of the Standard Model has motivated considerable interest in testing Newtonian gravity at ultra-short distances (less than or similar to 10(-4) m). New experiments which attempt to probe these distances will encounter formidable new obstacles, including large intermolecular forces, which could obscure weak new forces or small modifications to Newton's law of gravity. Here we will review the motivation for conducting such ultra short distance gravity experiments, and discuss some of the new problems that may arise in future experiments. Finally, we suggest a schematic design for a null experiment which would address some of these problems using the "iso-electronic" effect.