Surface creasing instability of soft polyacrylamide cell culture substrates

Efforts to understand and engineer cell behavior in mechanically soft environments frequently employ twodimensional cell culture substrates consisting of thin hydrogel layers with low elastic modulus supported on rigid substrates to facilitate culturing, imaging, and analysis. Here we characterize how an elastic creasing instability of the gel surface may occur for the most widely used soft cell culture substrate, polyacrylamide hydrogels, and show that stem cells respond to and change their behavior due to these surface features. The regions of stability and corresponding achievable ranges of modulus are elucidated in terms of the monomer and cross-linker concentrations, providing guidance for the synthesis of both smooth and creased soft cell substrates for basic and applied cell engineering efforts.