This grant will focus on understanding how the molecular structure of novel polymers affects their ability to contract - similar to how natural muscles contract and lengthen to generate motion and force. Most soft biological materials rely on the efficient transfer of mechanical work from nanoscopic molecular motors to the macroscale. This is ensured by a sophisticated and architected internal network. That network consists of molecular machines that cooperatively “pull†on polymer “ropesâ€. This action is a microscopic tug-of-war that drives contraction. This project will focus on the replication of such mechanisms by combining artificial molecular machines (rotaxanes). For this, the project will develop a multiscale model, complemented by experiments, that can bridge active molecular mechanisms and the macroscopic response. Outcomes of this research will enable the creation of active materials/machines with a myriad of biomechanical applications. It will also promote collaborations and inspire a new generation of researchers at the edge of mechanics and materials science. Planned activities include active learning modules for high-school and undergraduate students, the involvement of these students in research, and the dissemination of research findings in social media.
The specific goal of the research is to understand the relationship between molecular mechanisms in slide-ring gels, the energy input in molecular motors, and the emergent contraction of the macroscopic gel. For this, the research project will integrate theoretical/computational mechanics, chemical synthesis, and mechanical characterization in a feed-back loop, where model and experiments will learn from one-another. The model, based on statistical mechanics, will provide a clear connection between molecular processes (ring sliding, ring collapse, …) and the macroscopic rheology, elasticity, and contraction. In turn, experiments will be guided by the model so that a rational design can be achieved. The objectives of the project are specifically to (a) develop a model for isotropic topological gels to connect molecular architecture and mechanical response, (b) use this model to explore the mechanics of anisotropic slide-ring/cellulose networks, and (c) investigate and identify conditions that amplify the force transfer across scales during contraction. Through these aims, the project will advance the inner workings of slide ring networks to be used as molecular machines and enable the rational development of a biomimetic material capable of contracting as does natural muscle.
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.
