Mechanics of Elastoactive Structures

This award supports a research project that investigates the dynamics and control of active elastic systems. In nature, fish, birds, and other entities capable of movement display complex choreographies when interacting in dense groups, even without a centralized conductor to guide them. These complex behaviors hold great promises in engineering, where crowds of micro-robots could coordinate their actions to complete a global task. This project hypothesizes that linking “mindless” active units to spring-like structures is a pathway for achieving such a vision. The research activities will show how to program assemblies of elastically coupled active units that perform complex tasks, e.g., “solving a maze”, although they have no traditional sensing or information-processing capabilities. This work will advance our fundamental understanding of the “mechanical intelligence” achievable by active elastic systems and could translate into new capabilities in the field of soft robotics. Concurrently, the project provides a simple, modular, and inexpensive experimental platform to illustrate abstract concepts during teaching and outreach efforts and delivers an interdisciplinary learning experience for graduate and undergraduate students. This project aims to demonstrate that we can leverage flexural structures to coordinate and program stochastically moving small-scale components. To this end, the researchers will devise a system where activity meets nonlinear elastic deformations. They will experiment with elasto-active structures comprising long and thin elastic beams connected to active agents and develop theoretical models and numerical simulations to rationalize their mechanics. Those agents are centimetric rigid-bodied micro-robots that use vibration to "walk" across a flat surface. The project first focuses on the spontaneous self-oscillations observed when a beam is clamped on one end and loaded by a micro-robot on the other end. This system will be used to establish a minimal model that couples Langevin dynamics and the Kirchhoff equations for elastic rods. The project will next study the "runners" that form when a beam is loaded by a micro-robot at each end, resulting in the beam buckling and moving across the plane. The interaction of these runners with boundaries, e.g., planar reflection, interaction with obstacles, and passage through a slit, will be examined to elucidate the contributing factors to the runners’ ability to solve complex mazes. Finally, the project will explore systems with three or more micro-bots involved, enabling run-and-tumble motions and wave propagation, thereby expanding the operating modes of these elastically coupled active agents. 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.