Eliminating the challenges associated with physically oscillating contact instruments

The material properties of soft matter systems are measured with rheometers and tensile testing instruments whenever there exist few limitations on sample volume and fixturing where samples can be prepared specifically to work with the hardware of a given instrument. By contrast, indentation methods are advantageous for measuring material properties when sample preparation and geometry are highly constrained, which is often the case with tissue samples, hydrogel coatings, or soft objects with defined shapes like contact lenses. However, many soft matter materials exhibit frequency-dependent moduli, which are challenging to account for using the simple models of Hertz and Winkler. In this talk I will review our recent work to developed a Fourier-analysis method that leverages the Kramers-Kronig relations to extract frequency dependent elastic and viscous moduli from Force-indentation curves, eliminating the challenges associated with physically oscillating contact instruments.