Mechanical characterization of modulus-tunable and surface-modifiable polydimethylsiloxane with AFM

Abstract

In this study we investigated two polymeric reaction systems to fabricate stiffness-tunable and surface-modifiable polydimethylsiloxane (PDMS), a biomaterial commonly used in microfluidic devices for medical diagnostics and single-cell dynamics study. Using thiol-ene photochemistry, we gained insights about how different reaction variants, such as pre-polymer molecular weight, functional group ratio, and UV exposure time affect the stiffness of the cross-linked network. We compared different techniques for measuring stiffness and realized the advantage of atomic force microscopy (AFM) nano-indentation in characterizing the stiffness of soft, heterogeneous materials such as PDMS. We further applied what we learned from the thiol-ene system to platinum-catalyzed hydrosilylation reaction to study the effects of collagen adsorption on native as well as plasma-oxidized PDMS in terms of the dependence of the AFM-measured mechanical properties on surface chemistry.