Toward Rational Design of Biotic-Abiotic Machines

We describe ongoing efforts to model the dynamics of light-actuated soft machines consisting of a reconstituted active biopolymer network tethered to passive soft supports. Force generation in organisms often features an actively driven polymer network, such as the actomyosin cortex, anchored to structural proteins. The modern availability of purified cytoskeletal proteins and click chemistry allow the creation of devices that mimic the generation and transmission of force in living tissues. We consider an active gel made of actin crosslinked and driven by myosin II minifilaments, bound to PEG-DA hydrogel slabs using the biotin-streptavidin system. Owing to the rich design space of such a device, a high-throughput method for anticipating the behavior of a system with given gel moduli, actin concentration, degree of crosslinking, and motor activity is highly desirable. Our method couples an agent-based model of an active actomyosin network to a finite element-based description of a passive gel and uses Langevin dynamics to simulate the behavior of this composite system. We will discuss the utility of this technique in identifying rational design principles for soft actuators powered by chemical potential energy.