High‐Sensitive Spatiotemporal Distribution Imaging of Compression Stresses Based on Time‐Evolutional Responsiveness

Abstract Mechanoresponsive materials have been studied to visualize and measure stresses in various fields. However, the high‐sensitive and spatiotemporal imaging remain a challenging issue. In particular, the time evolutional responsiveness is not easily integrated in mechanoresponsive materials. In the present study, high‐sensitive spatiotemporal imaging of weak compression stresses is achieved by time‐evolutional controlled diffusion processes using conjugated polymer, capsule, and sponge. Stimuli‐responsive polydiacetylene (PDA) is coated inside a sponge. A mechanoresponsive capsule is set on the top face of the sponge. When compression stresses in the range of 6.67–533 kPa are applied to the device, the blue color of PDA is changed to red by the diffusion of the interior liquid containing a guest polymer flowed out of the disrupted capsule. The applied strength ( F /N), time ( t /s), and impulse ( F · t /N s) are visualized and quantified by the red‐color intensity. When a guest metal ion is intercalated in the layered structure of PDA to tune the responsivity, the device visualizes the elapsed time ( τ /min) after unloading the stresses. PDA, capsule, and sponge play the important roles to achieve the time evolutional responsiveness for the high‐sensitive spatiotemporal distribution imaging through the controlled diffusion processes.