Feedbacks in light-active soft materials

Imitating the self-regulated motions of natural species allows for novel applications in inanimate material systems. These applications include autonomous robotic systems, adaptive devices, and auto-energy harvesting. However, significant challenges exist in accurately controlling stimulus-induced deformations and establishing a reliable relationship between external energy fields and material deformations. In this study, we demonstrate that a simple light-triggered bending actuation in smart material systems based on liquid crystal elastomers is influenced by an opto-mechano-optical feedback mechanism. The pre-curved geometry enables enhance of light absorption upon photothermally induced deformation (from bent to flat), followed by a reduce of energy absorption upon further deformation (from flattening to bending toward the light). This strong nonlinearity in stimulus-induced deformability is governed by positive and negative feedback, and we experimentally verified these mechanisms using a thermal camera. Our results reveal the ubiquitous feedback nature of most light-active polymer systems.