CAREER: Deformation and interfacial slip in two-dimensional material heterostructures

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This Faculty Early Career Development (CAREER) Program project will explore the fundamental limits of friction and how to utilize slip at nanoscale interfaces in atomic membranes composed of two dimensional materials. An important capability of membranes is to relieve stress through the introduction of interfacial slip or out-of-plane crumpling. Two-dimensional interfaces also display emergent nanoscale properties like superlubricity where the friction decreases by a factor of 100. Yet, it is not well understood how slip and superlubricity at interfaces affects the mechanics of nanoscale membranes made from heterostructures of multiple materials. The success of this study will lead to the design of electronic materials which actively utilize slip and deformation to become 10-100 times more pliable than state of the art stretchable technologies like silicon microelectromechanical systems or organic electronics. Slippable devices made from 2D materials have applications as low-footprint, low power sensors, tunable signal processors, or energy harvesting systems in wearable electronics. As part of the project, the PI will also create a project-based educational outreach activity in which students will design a laser light show and deliver them to schools with primarily minority populations and summer STEM camps for underrepresented groups. The PI will continue creating research mentoring opportunities for undergraduates including underrepresented minorities and introduce a new project-based nanoscale engineering course.The lack of covalent bonds and the incommensurate structure at van der Waals interfaces in 2D materials heterostructures leads to superlubricity and easy slip between layers. This program will examine the impact of interlayer friction and slip on 2D heterostructures under shear, bending, and tensioning. Objective 1 will build a theoretical foundation to quantify friction, adhesion, slip and superlubricity at incommensurate heterostructure interfaces through atomic scale simulation and multiscale modeling. Objective 2 will experimentally probe the friction of incommensurate interfaces under shear by sliding micropillars built from 2D heterostructures and measuring the forces with lateral force microscopy. Objectives 3 and 4 will respectively study the impact of slip in crumpled 2D membranes and resonant drumheads. These results are anticipated to reveal the interplay between interlayer alignment and superlubricity, when smooth sliding or stick-slip occurs, and slip-mediated nanomechanical scaling laws and moduli. The new knowledge will be used to predict and design the pliability of 2D heterostructure atomic membranes lying at the forefront of technologies and applications.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.