Visualizing and Quantifying Impact with Mechanochromic Sensing Paints Based on Self-Assembled Polydiacetylene-Silk Core-Shell Vesicles.

Rapid detection and quantification of mechanical impact on surfaces is relevant for many fields, as it enables monitoring of material stresses and integrity or to assess the physiological effects of force on humans for concussions, gait, or blast dosimetry, among others. Accurate and quantitative detection of impact force, especially at high values (100-770 N), is challenging and often relies on electronic transduction and interfaces, with associated limitations in integration, shaping, and scalability. We present here a mechanochromic paint as a simple alternative for impact detection and visualization. The paint is based on the self-assembly of polydiacetylene (PDA) and regenerated silk fibroin protein (SF) into core-shell vesicles, which exhibit an irreversible mechanochromic transition from blue to red upon impact. The paint enables the tracking of the impact history on the applied material with a colorimetric response that is directly proportional to the impact energy across a broad sensing range of 100-770 N (corresponding to 100-1000 MPa) and has wide utility given by its ability to be interfaced or integrated in a wide variety of material formats, as illustrated by through several demonstrator devices.