ERI: Tailoring Piezoresistive Effect of Nanocomposites using Topological Design

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Polymer nanocomposites hold significant potential as multifunctional electronic components, which can provide tremendous novel opportunities for advancing various applications, such as structural health monitoring (SHM), healthcare, robotics, and national security and economy. Among the unique properties of nanocomposites, strain sensitivity (i.e., piezoresistive effect) has been commonly observed. High piezoresistive effect of nanocomposites can remarkably benefit strain sensing in SHM, wearable sensors, and robotics, among others. On the other hand, piezoresistive effect can also be undesirable and hinder the applications of nanocomposites as electronic components for flexible displays, energy harvesting, and multimodal sensors. Therefore, the piezoresistive effect of nanocomposites needs to be effectively designed and tuned to optimal ranges depending on target functionality. Current design approaches mostly focus on engineering the material components of nanocomposites, which generally entail empirical and inefficient processes due to the complex process-structure-property relationships of resulting material systems. To address this challenge, this research aims to establish an innovative design strategy based on topological design to engineer the piezoresistive behavior of nanocomposites in a predictable manner. This project will provide hands-on research opportunities to engage underrepresented and first-generation college students in developing nanomaterial-based electronics. In addition, a new course and several multidisciplinary capstone design projects will be developed based on this research project, which will enrich and improve the engineering education at a minority-serving institution. This project will investigate the correlation between the piezoresistive effect of nanocomposites and topological design by focusing on three research thrusts. First, two main categories of topologies, including stress-concentrating and stress-releasing topologies, will be designed for altering the stress distribution in the material system. Their mechanical responses to external loads will be characterized via finite element analysis and load tests. Second, carbon nanotube-, graphene-, and silver nanowire-based piezoresistive nanocomposites will be fabricated using additive manufacturing techniques and be patterned to form the pre-designed topologies. Electromechanical experiments will be conducted to characterize and compare the piezoresistive response of the patterned nanocomposites. In addition, statistical analysis will be performed to investigate the correlation between the piezoresistive behavior and the topological design. Third, to better understand the piezoresistive performance of patterned nanocomposites, stochastic material models will be developed by statistically reconstructing the microstructures of nanocomposites based on microscopic images. Then, the material models will be used for simulating the electromechanical responses of different topologies. The simulation results will be compared with the experimental measurements. This research will generate new fundamental knowledge on the effects of topological design on the piezoresistive behavior of nanocomposites, which will enhance the design efficiency and performance of nanomaterial-based multifunctional electronics.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.