Concurrent spatial mapping of the elasticity of heterogeneous soft materials via a polymer-based microfluidic device

Abstract

In this paper, built upon a polymer-based microfluidic device, a novel experimental technique called concurrent spatial mapping (CSM) is presented for measuring the spatially-varying elasticity of heterogeneous soft materials. Comprised of a single compliant polymer microstructure and a set of electrolyte-enabled distributed resistive transducers, this device is capable of detecting continuous distributed loads. In this experimental technique, a rigid probe is employed to press a material specimen against the device with precisely controlled displacements, and consequently the spatially-varying elasticity of the specimen translates to continuous distributed loads acting on the device, where continuous distributed loads give rise to continuous deflection of the polymer microstructure and register as discrete resistance changes at the locations of the distributed transducers. Performance characterization is first conducted on the device as a control experiment. Then, CSM is implemented on several heterogeneous and homogeneous polydimethylsiloxane specimens, as well as a rabbit tissue specimen. The associated data analysis is performed on the measured data for extracting the spatially-varying load-deflection relations of these specimens. In conjunction with its dimensions, the extracted spatially-varying load-deflection relations of a specimen result in its spatially-varying elasticity by the related theoretical formula. For the first time, this paper demonstrates the feasibility of using a single polymer-based microfluidic device to concurrently map out the spatially-varying elasticity of heterogeneous soft materials. As a result, CSM will pave the way for efficiently examining biological tissues and cell-seeded engineering scaffolds, while without excluding the interaction among neighboring compositions in such materials.