Development of a micro-sized thermal contact sensor for inspection of surface defects

This paper presents an experimental study on a thermal element, which is designed to be used as a sensing device that detects a small amount of frictional heat due to a contact with nanometre-scale defects on smoothly-finished surfaces. A prototype of the thermal element, which is a thin-film resistance, is fabricated by using photolithography processes, and its sensitivity on the contact detection is investigated through some experiments, in which the thermal element is scratched by a micro-sphere controlled by PZT actuator in both X- and Z-directions so that a contact between the thermal element and defects can be simulated. Influences of an interference height and relative velocity between the thermal element and the target surface on the output of the thermal element at the contact detection are verified.