Thermal imaging with tapping mode using a bimetal oscillator formed at the end of a cantilever

Thermal detection based on the thermal shift of the resonant frequency of a bimetal resonator (Al/Si) is presented and demonstrated. The bimetal oscillator with a tip is fabricated at the end of a commercial silicon cantilever. The bimetal oscillator and the silicon cantilever have a resonance frequency of 441 and 91 kHz, respectively, and the measured temperature coefficients of the resonant frequency are -127× 10-6 /K and -115× 10-6 /K, respectively. It is demonstrated that self-oscillated resonant frequency of the bimetal oscillator changes in response to heat from a microheat source. Simultaneous measurements of topography and temperature profile with the temperature resolution of 0.12 K on a glass substrate heated using a thin chromium film microheater are successfully demonstrated. These results show potential abilities of the mechanical resonant thermal sensor.