Measuring average tip-sample forces in intermittent-contact (tapping) force microscopy in air

A method to measure the average normal force on a surface produced by intermittent-contact (tapping) force microscopy is presented. This force is determined by measuring the average deflection of a calibrated piezoresistive cantilever in intermittent contact with an oscillating active cantilever. Results obtained with this method are presented for a two-state cantilever motion where the piezolever force is higher for the state with the lower amplitude of vibration.