Determination of the deformations in polymeric nanostructures using geometric moiré techniques for biological applications

The nanometer-scale in-plane deformation of a PDMS nanostructure array was demonstrated using a geometric moiré technique. The polymer nanostructures with cylindrical profile were fabricated by using the combination of e-beam lithography, reactive ion etching, and replica molding. The moiré pattern is generated by the inference between the polymer nanostructures and the scanning lines of a CCD video camera. A uniform thermal expansion was induced in the polymer nanostructures. The moiré pattern change was observed at different temperatures from 298 to 398 K. The change of the strain/pitch in the nanostructures as the temperature varied was calculated from the pure extension and the angular moiré fringes. The results show the feasibility of using such polymer nanostructures as force sensors to measure the mechanical forces on the order of a few nanonewtons or less. This work has a representative application in mechanics study of the biological objects, e.g. living cells and protein, under their environmental conditions.