Torsion balances are almost ideal detectors of weak forces due to their low stiffness, noise and sensitivity to ground tilt. Their dynamics, however, make it difficult to measure forces that have sub-mm ranges. In Birmingham we are developing the experimental techniques, based on previous work, to eventually allow reliable measurements of the inverse square law of gravity down to mass separations of the order of 10ľm. This work has revolved around the superconducting torsion balance and the proof-of-concept air bearing suspension projects. I will discuss these experiments and my involvement in them during my PhD. This has included designing, building and implementing a capacitive displacement sensor for measuring the rotation of the test mass of the superconducting torsion balance, experimentally demonstrating the insitu tuning of the centre-of-buoyancy and rotational stiffness of a suspended mass on the air bearing suspension, as well as modelling the magnetic forces in the superconducting torsion balance.