A nondestructive method that is based on modified atomic force ultrasonic microscopy (AFUM) methods has been developed for characterizing nanomaterials. The technology allows imaging and quantifying of material properties at the surface and subsurface levels. The technology reveals the orientation of nanotubes within a composite structure and offers the ability to determine subsurface characteristics without destroying the nanomaterial structure. The method is widely applicable for basic nanomaterials characterization, including distribution and orientation of particles in a nanocomposite, localized elastic constants and changes in elastic constants, adhesive surface properties, sound velocity, and material damping coefficient.

The technology is:

  • Nondestructive: Previous methods require destructive sampling.
  • Ubiquitous: A wide range of materials characterization for nanomaterials is enabled.
  • Elegant: Design is based on modifications to commercially available atomic force ultrasonic microscopy (AFUM) hardware.

The manufacturing of nanocomposites produced by the embedding of nanostructural constituents into matrix materials has placed increased demands on the development of new measurement methods and techniques to assess the microstructure physical property relationships of such materials. Although a number of techniques are available for near-surface characterization, this new method allows assessment of deeper (subsurface) features at the nanoscale.

This new scanning probe microscope methodology is called resonant difference frequency atomic force ultrasonic microscopy (RDF-AFUM). It employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope engages the sample top surface. The cantilever is driven at a frequency differing from the ultrasonic frequency by one of the contact resonance frequencies of the cantilever. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave at the sample surface generate difference-frequency oscillations at the cantilever contact resonance. The resonance-enhanced difference-frequency signals are used to create amplitude and phase-generated images of nanoscale near-surface and subsurface features.

The technology offers wide-ranging market applications such as functional nanocomposites for aerospace structures, biomedical uses such as infusion of tissue with nanoparticles, verification of drug delivery to tissue targets, and sensors/actuators.

This work was done by John Cantrell and Sean Cantrell of Langley Research Center. For further information, contact the Langley Innovative Partnerships Office at (757) 864-8881. LAR-17440-1

NASA Tech Briefs Magazine

This article first appeared in the June, 2014 issue of NASA Tech Briefs Magazine.

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