Article: Paretkar D, Xu XJ, Hui CY, Jagota A; (2014) Flattening of a Patterned Compliant Solid by Surface Stress, Soft Matter, 10(23):4084-4090
Abstract: We measured the shape change of periodic ridge surface profiles in gelatin organogels resulting from deformation driven by their solid-vapor surface stress. A gelatin organogel was molded onto polydimethylsiloxane (PDMS) masters having ridge heights of 1.7 and 2.7 mu m and several periodicities. Gel replicas were found to have a shape deformed significantly compared to their PDMS master. Systematically larger deformations in gels were measured for lower elastic moduli.
Measuring the elastic modulus independently, we estimate a surface stress of 107 +/- 7 mN m(-1) for the organogels in solvent composed of 70 wt% glycerol and 30 wt% water. Shape changes are in agreement with a small strain linear elastic theory. We also measured the deformation of deeper ridges (with height 13 mu m), and analysed the resulting large surface strains using finite element analysis.