Improved design of optical-microforce sensor with high thermal-mechanical stability for insulation charge ellipsometer testing application

Optical-microforce sensor is the core of the sensing module for the insulation charge ellipsometer testing, whose thermal-mechanical stability directly affects the charge measurement reliability. In this paper, based on molecular simulation, the improved design for SU-8 photoresist-based optical-microforce sensor is proposed. It is found that carboxyl-functionalized carbon nanotube/SU-8 photoresist composite system with 75 % cross-linking index possesses the comparatively better thermal-mechanical stability. Then, based on the photolithography process, modified and unmodified optical-microforce sensors are prepared. Meanwhile, the thermal-mechanical stability is evaluated from the experimental perspective. The experiment is consistent with the molecular simulation, showing that compared with the unmodified optical-microforce sensor with measurement fluctuation of 17.6 %, the modified sensor exhibits better thermal-mechanical stability, whose measurement fluctuation is only 5.3 % during the temperature range of 25–100 °C. Further, the optical-microforce sensor measurement performance evaluation platform is built. It is shown that the modified sensor could achieve the response to different frequency, different magnitude elastic wave and picosecond pulse width elastic wave, which could be applied in the insulation charge ellipsometer testing application.