Device and method for monitoring surface condition of contact surface of detected object

A method for monitoring a contact surface of a detected object, the method comprising:

• providing a surface monitoring device, wherein the surface monitoring device and the detected object are disposed on a substrate and the surface monitoring device as provided includes:
• providing a resonant mechanical part, having a contact tip adjacent to the contact surface by a preset gap in a static state;
• providing a driving circuit, applying an input signal of alternating current (AC) to drive the resonant mechanical part to cause the contact tip to vibrate with respect to the contact surface at a plurality of sampling frequencies, wherein the contact tip substantially hits the contact surface in a tapping bandwidth within the sampling frequencies;
• and
• providing an analysis circuit to analyze a ratio of an output voltage to an input voltage of the input signal and determine the tapping bandwidth, wherein the ratio in the tapping bandwidth is jumping to a flatten phase;
• and
• monitoring the tapping bandwidth to determine a change of the contact surface in physical property.