Force‐Modulated Luminescent Film: Micro‐Newton‐Level Stress Sensing by Force‐Induced Regulation of Donor–Acceptor Electron Coupling

The development of stretchable luminescent materials with high sensitivity, clear luminescence mechanism, and good biocompatibility is a long‐term challenge in the field of flexible electronics and intelligent sensing. In this paper, a self‐supporting luminescent film (CS‐HBAGE‐TPA‐NDI film) based on modified chitosan was prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization of modified chitosan (CS) with a double bond, VP‐NDI with a symmetrical structure, and n‐vinylcarbazole (NVC) under the action of RAFT reagent TPA‐TTC and initiator azobisisobutyronitrile (AIBN). The CS‐HBAGE‐TPA‐NDI film not only exhibits a tensile rate of up to 180% and a unique rubbery state behavior (glass transition temperature of −8°C), but also achieves extremely sensitive tensile force detection (limit of detection (LOD) is 3.01 ± 1.2 µN). The significant enhancement of stretch luminescence is observed under force‐induced regulation of electron coupling between triphenylamine and naphthalimide. At the same time, a conceptual wearable pulse monitoring device was further proposed, reflecting the great potential of the material in converting physiological microscopic forces into optical signals. This work provides a new model for understanding the intermolecular electronic behavior in force‐modulated luminescence. It also opens the way for the development of next‐generation passive and bio‐friendly flexible optoelectronic devices.