On-Demand, Reversible, and Non-Contact Shape-Fixation of Microstructuresin UV Responsive Covalent Adaptable Network

Dynamic network exchange reactions enable covalent adaptable networks (CANs) to be malleable and reprocessable analogue of thermosetting polymers. Unlike conventional CANs, which rely on thermally activated network exchange reactions, a new CAN incorporating both UV- and heat-responsive disulfide bonds is introduced. UV irradiation at room temperature effectively accelerates the stress relaxation of this CAN, achieving results comparable to those obtained at elevated temperatures (> 100 °C) without UV irradiation. As a result, UV irradiation can be adopted as an on-demand, reversible, and non-contact shape-fixation method, eliminating the need for heat, toxic solvents, or support structures. To maximize the effectiveness of this approach, we employ the facile fabrication of three-dimensional (3D) staggered-overlapped microdenticles, mimicking sharkskin, that demonstrate non-contact/spatiotemporal shape fixation using UV light. To further investigate the dynamic characteristics of this system in response to temperature and/or UV, non-equilibrium molecular dynamics (NEMD) simulations were also performed.