Motion-Driven Self-Visualizing Soft Robots Enabled by Mechanoluminescent Tubular Fibers

Abstract

Motion-responsive optical sensing that directly visualizes deformation without external electronics is highly desirable yet remains difficult to implement in pneumatic soft robotic systems. In particular, integrating wired or battery-powered sensors into soft robots composed of low-modulus elastomers is challenging due to the mechanical mismatch between conventional sensors and highly compliant actuators. Here, we present a compliance-matched tubular mechanoluminescent (ML) fiber that enables battery-free visualization of pneumatic soft robot motion through deformation-induced light emission. The ML fiber is fabricated by encapsulating a self-recoverable ZnS:Cu-PDMS composite within an elastic silicone tube, forming a mechanically adaptive architecture that preserves large stretchability while maintaining stable ML responses under repeated deformation. Owing to the intrinsic compliance of the tubular structure, the fiber sustains tensile strains exceeding 200%. When integrated into a pneumatically driven soft robot in a woven network architecture, the ML fibers generate deformation-associated light emission from regions undergoing actuation, enabling qualitative visual monitoring of robotic motion without wiring, signal-processing circuits, or external power sources for sensing. This compliance-engineered ML fiber architecture provides a scalable strategy for embedding self-powered optical sensing into highly deformable soft systems and offers a versatile platform for self-visualizing soft robotics, wearable motion monitoring, and artificial skin interfaces.