Study On The Calibration Of The Spring Constant Of Microcantilever Based On Bending Method

Microcantilever is one of the most important tools for nano-scale measurementdue to its high sensitivity. It is widely used in surface morphology test andnanomanipulation as the probe of AFM. The spring constant of microcantilever has asignificant impact on the scanning speed or the accurate force measurement. Wepresent a novel cantilever calibration system，consisting of ultra-precision balance andoptical lever device. The spring constant was calculated by the Hook’s Law, while theforce and the deflection could be obtained by the balance and the optical leverrespectively. This dissertation mainly accomplished the setup of mechanicalconstruction and the design of measuring circuit based on FPGA. Seven kinds ofcantilevers were calibrated with this system and presented good repeatability andreliability, and the results are traceable.The achievement details include the followings:1. A general review of calibration methods was presented and comparisons of theiradvantages and disadvantages were discussed. A new calibration method wasproposed with the combination of ultra-precision balance and optical lever.2. Accomplished the calibration system and achieved the bending of thecantilever.The deflection of the cantilever was measured by the optical lever.3. Completed the measuring circuit of the calibration system based on FPGA,including the acquisition of current signals, the movement of the microcantilever andthe deflection. The interface has been designed.4. Seven kinds of microcantilever probes have been calibrated and the results werecompared with the thermal noise method.