Development of a Laser Driving Circuit for Force-Feedback in Atomic Force Microscopy

An atomic-force microscope (AFM) is a high resolution microscope using forces between a sharp probe and a sample surface. AFM creates images at nanoscale by measuring the vertical and lateral deflections of a sensitive cantilever. However, the conventional AFM has limited ability in measuring intermolecular interaction and high- speed imaging due to the cantilever’s mechanical instability called “snap-to contact problem.” To solve this problem, here we developed a laser driving circuit that can balance the cantilever by generating a counter force through force-feedback mechanism. The function of the laser driving circuit was demonstrated using a laser diode with the wavelength of 670nm (red color). We observed that the laser intensity increases as the input voltage increases and vice versa. The circuit also follows the square wave input signal well, showing that it is a high speed circuit. The developed circuit will address many critical issues related to the conventional AFM in measuring intermolecular interaction and high-speed imaging.