Oral: Spatiotemporal mechanical modulation of non-equilibrium DNA-polymer composites via topological tuning

Engineering non-equilibrium active materials that can sense, respond, and transform is at the frontier of materials research. As such, state-of-the-art active matter experiments have focused on reproducing biological active matter such as motor-driven cytoskeletal systems. However, these systems are typically noisy and heterogeneous with activity that is short-lived and difficult to control and tune. Here, we circumvent these limitations by leveraging well-studied and widely used synthetic polymers to serve as mechanical scaffolds that we 'activate' by introducing topologically-active DNA. DNA can undergo various enzymatic topological transformations (concatenation, fragmentation, annealing, and twisting) which are essential for biological processes such as replication and repair. Here, we harness these topological conversions to induce time-varying mechanical properties of composites of polystyrene sulfonate (PSS) and DNA. In another design approach, we incorporate photo-responsive synthetic polymers to crosslink DNA, thereby engineering programmable gelation of bio-synthetic composites with kinetics and mechanical properties tuned by the illumination properties. These two design routes, enzymatic and photo-responsive activity, provide orthogonal molecular knobs for spatiotemporal tuning of DNA-based bio-synthetic composites.