1. A sensor for determining the presence of an object, the sensor comprising: first and second flexible conductor elements separated by a separation distance and having a capacitance dependent on the separation distance; and a non-conductive compressible element interposed between the first and second flexible conductor elements, wherein the non-conductive compressible element compresses in response to an object applying a force to at least one of the first and second flexible conductor elements such that the separation distance between the first and second flexible conductor elements decreases, wherein the capacitance of the first and second flexible conductor elements changes in response to the separation distance between the first and second flexible conductor elements decreasing.