Nanoscale dynamic mechanical analysis via atomic force microscopy (AFM-nDMA)
AssigneeBruker Nano, Inc.
InventorsSergey Osechinskiy, Anthonius Ruiter, Bede Pittenger, Syed-Asif Syed-Amanulla
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Abstract
An atomic-force-microscope-based apparatus and method including hardware and software, configured to collect, in a dynamic fashion, and analyze data representing mechanical properties of soft materials on a nanoscale, to map viscoelastic properties of a soft-material sample. The use of the apparatus as an addition to the existing atomic-force microscope device.
Claims22
A method for determining a mechanical property of a soft viscoelastic sample with an atomic-force-microscope (AFM)-based system, the method comprising:
- while maintaining at least one of
- i) an average sample-loading force, generated by a probe of the system, and
- ii) an area of contact between a tip of the probe and a surface of said viscoelastic sample configured as a thin film or a composite material with a Young modulus value no higher than 10 GPa
- to be substantially constant, repositioning the probe of the system towards the surface of said viscoelastic sample until a cantilever of the probe is deflected by a pre-determined amount from a nominal orientation of the cantilever;
- and
- measuring, at a set of frequencies within a range from 0.001 Hz to 1,000 Hz, a viscoelastic parameter of the surface of said sample in absence of using either a lock-in detection or a Fast-Fourier-Transform based analysis.
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:
- a position-detecting system configured to detect a deflection of a cantilever of a cantilevered probe of the AFM as a function of at least time and to generate data representing said deflection;
- an excitation electronic circuitry configured to generate a first oscillatory signal including at least a single sinusoidal signal at a frequency within a range from 0.001 Hz to 1,000 Hz;
- a feedback electronic circuitry electrically connected with the position-detecting system and the electro-mechanical sub-system and configured to monitor both a mean of said first oscillatory signal and an oscillatory component of said first oscillatory signal;
- an electro-mechanical sub-system cooperated with the excitation electronic circuitry and the feedback electronic circuitry and configured:
- to reposition one 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 cause a mechanical oscillation of said one of the sample and the probe with respect to another of the sample and the probe as a result of acquiring the first oscillatory signal transferred from the excitation electronic circuitry;
- and
- based on monitoring output produced by the feedback electronic circuitry, to maintain said one of the sample and the probe in a position, with respect to the other of the sample and the probe, in which an average sample-loading force generated by the probe during said mechanical oscillation is kept substantially constant;
- a programmable processor in electrical communication with at least the electro-mechanical sub-system and a position-detection system and programmed:
- to transfer the first oscillatory signal from the excitation electronic circuitry to the electro-mechanical sub-system;
- to suspend an operation of the electro-mechanical sub-system for a relaxation period of time sufficient for relaxation of a creep of a surface of the sample that is caused by repositioning of said one of the sample and the probe with respect to the other of the sample and the probe;
- and
- to acquire said data from the position-detection system to determine a viscoelastic parameter after the relaxation period of time has lapsed.
Dependencies are inferred from the claim text.