Electric field induced changes in the swelling of a strong polyelectrolyte brush will be investigated using neutron reflectivity. A poly(styrene sulphonate), PSS, brush will be attached to a silicon substrate which will form half of a parallel plate capacitor structure. The capacitor will be filled with deuterium oxide. PSS is fully ionised in neutral water or deuterium oxide and hence is in its fully stretched away from the substrate. Application of voltages to the capacitor will result in charge being stored on the surfaces of the electrodes and hence the brush. This charge will modify the ionisation of the brush and hence its degree of swelling/stretching.