Nanoscale dynamic mechanical analysis via atomic force microscopy (AFM-nDMA)

An apparatus configured to determine a mechanical property of a surface of a viscoelastic sample with an atomic-force-microscope (AFM) hardware, the apparatus comprising:

• an excitation electronic circuitry configured to generate an excitation force signal causing, in operation of the apparatus, one of (i) a cantilever of a cantilevered probe of the apparatus and (ii) the sample undergo a first extremal displacement from a nominal position thereof only at a beginning of a pre-determined time period and a second extremal displacement from the nominal position only at an end of the pre-determined time period;
• an electro-mechanical sub-system in operable cooperation with the excitation electronic circuitry, the electro-mechanical system configured:
• to reposition, in response to the excitation force signal, said one of the cantilever and the sample with respect to another of the sample and the probe until a point where the cantilever is deflected by a pre-determined amount from a nominal orientation of the cantilever;
• to maintain the probe in a position, with respect to the surface of the sample, in which at least one of
• i) an average sample-loading force, generated by the probe, and
• ii) an area of contact between a tip of the probe and the surface of the sample is kept substantially constant;
• a position-detecting system configured to detect a deflection of the cantilever as a function of at least one of a temporal factor and a spatial factor characterizing the operation of the apparatus;
• a programmable processor in electrical communication with the electro-mechanical sub-system and the excitation electronic circuitry and programmed at least:
• to suspend an operation of the electro-mechanical sub-system for a relaxation period of time that is sufficient for relaxation of a creep of the surface, wherein the creep has been caused by repositioning of one of the sample and the probe with respect to another of the sample and the probe;
• and
• to acquire data, from the position-detecting system, to determine a viscoelastic parameter of the surface of the sample.