CAREER: Determine the Roles of Material Heterogeneity and Thickness Variability on the Stability of Thin Membranes

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This Faculty Early Career Development Program (CAREER) award will support integrated research and educational efforts to generate new knowledge of how material and thickness non-uniformity (also referred to as heterogeneity) in thin, bio-compatible materials and bio-tissues affect their mechanical behaviors under various deformation conditions. Examples of such materials include ultra-thin wearable bio-sensors, the eardrum membrane, and the heart valves. The award supports fundamental research that will enable a currently unavailable, non-destructive material characterization protocol for obtaining the material property maps, which will allow the deformation and stability of these materials to be better understood. The innovative approach in this project is expected to promote scientific advancement in new mechanics knowledge that is important for a wide range of healthcare and biomedical applications, thereby impacting the national health and economy. The project will provide opportunities to train graduate and undergraduate students in the important interdisciplinary areas of mechanics, materials science, and biomedical devices. The educational outreach activities are designed to engage young children and under-represented minorities in STEM education, with the goal of enlarging the STEM talent pool for the nation.Many important natural and synthesized heterogeneous thin membranes wrinkle under very small loads. Stability of thin structures has long been a canonical problem in the mechanics community. Yet to date, huge discrepancies in buckling loads between theories and experiments are still usually accounted for by empirical corrections. There is a clear lag in understanding for predicting the buckling loads of thin heterogeneous membranes. The objective of this CAREER project is to test the hypothesis that a higher degree of heterogeneity in thin membranes reduces the critical buckling loads. The research approach is to experimentally measure and compare the buckling loads of a set of thin membranes of various degrees of heterogeneity ranging from highly heterogeneous to homogeneous. Fluorescence stereo microscopy and inverse finite element analysis will be combined to extract the material property distributions and thickness variability, and then a theory-guided numerical model will be developed to identify a quantitative degree of heterogeneity and elucidate how it is related to reduced buckling loads.This project is jointly funded by the Civil, Mechanical, and Manufacturing Innovation program (CMMI), and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.