Advancing Nanoscale Indentation Measurements Toward Quantitative Characterization of Polymer Properties

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The ultimate objective of instrumented indentation testing is to obtain absolute measurements of material properties and behavior. To achieve this goal, accurate knowledge of the shape of the indenter tip is required. For indentation measurements involving sub-micrometer scale contacts, accurate knowledge of the tip shape can be difficult to achieve. In this presentation, a technique referred to as blind reconstruction is applied to the measurement of tip shapes of indenters used with the atomic force microscope (AFM) to indent polymeric materials.

The AFM has been used recently to make nanoscale indentation measurements and is particularly useful for evaluating the mechanical response of polymeric materials. These measurements can be made using AFM cantilever probes and operating the AFM in force mode with some modifications to account for lateral tip motion. Because the AFM was not specifically designed as an indentation device, other complications can arise due to instrumental uncertainties such as piezo hysteresis, piezo creep, and photodiode nonlinearities.