Improved Quantification of Nanoscale Viscoelasticity Measurements by Nanorheological Atomic Force Microscopy

Abstract

Nanorheological atomic force microscopy (AFM) is a measurement technique that maps dynamic viscoelasticity with nanoscale spatial resolution. The technique combines dynamic measurements with quasi-static force curve measurements, allowing quantification of the contact area using a theoretical model of contact elasticity and, therefore, the dynamic modulus. However, the nano-viscoelasticity measured by nanorheological AFM is not in perfect agreement with the macro-viscoelasticity measured by a rheometer. To improve the quantitative performance of the dynamic modulus, a variable was introduced to correct for the difference from the contact area of Johnson-Kendall-Roberts theory. The load dependence of the storage stiffness of polydimethylsiloxane (PDMS) and styrene-butadiene rubber (SBR) was investigated to determine variables for each measurement frequency. The novel analytical method gives results in better agreement with the macroscopic measurement method.