Building Active Solids: Geometric Design Meets Chemomechanical Oscillations

Synopsis

Living organisms can change their own shape with remarkable precision, using soft tissues that sense, actuate, and respond without any external control. These active solids are central to understanding biological motion and morphogenesis, yet building synthetic materials that behave this way remains difficult. In this talk, I will describe our efforts to design and fabricate such materials. I will start with geometry: how uneven swelling can encode a reference geometry for a thin sheet, and how the resulting geometric frustration can drive out-of-plane buckling, symmetry breaking, and exotic mechanical properties. I will then show how we put these ideas into practice with a 4D printing method for hydrogels that gives us full control over the deformation distribution and the geometric frustration across a printed structure. In the last part of the talk, I will turn to self-oscillating gels, hydrogels that move by themselves, powered by the Belousov-Zhabotinsky (BZ) chemical reaction. I will review what we have learned about how chemical oscillations drive mechanical motion in these active materials and then share new results where we program the spatial distribution of the chemomechanical activity and watch new shape dynamics emerge. Together, these projects combine insights from physics, biology, and mathematics to move toward true synthetic active solids: soft materials that change shape autonomously.