Facile determination of the Poisson’s ratio and Young’s modulus of polyacrylamide gels and polydimethylsiloxane

Abstract

ABSTRACTPolyacrylamide hydrogels (PAH) and polydimethylsiloxane (PDMS) are two soft materials often used in cell mechanics and mechanobiology, in manufacturing lab-on-a chip applications, among others. This is partly due to the ability to tune their elasticity with ease, in addition to various chemical modifications. For affine polymeric networks, two (of three) elastic constants – the Young’s modulus (E), the shear modulus (G), and the Poisson’s ratio (ν) – describe the purely elastic response to external forces. However, the literature addressing the experimental determination of ν for PAH (also sometimes referred to as PAA gels in the literature) and PDMS is surprisingly limited when compared to the literature reporting values ofEandG. Here, we present a facile method to obtain the Poison’s ratio and Young’s modulus for PAH and PDMS based on static tensile tests, and cross-correlate these values with those obtained via a second independent method, shear rheology. We show that: i) the Poisson’s ratio may vary significantly from the value for incompressible materials (ν = 0.5), and ii) find a high degree of agreement between shear rheology and macroscopic static tension tests for PAH but not PDMS.Abstract Figure