Angle-Insensitive Fabry–Perot Mechanochromic Sensor for Real-Time Structural Health Monitoring

Colorimetric sensors that respond to mechanical stimuli have garnered increased attention for various applications such as healthcare, display, electronic skin, and camouflage. To date, these mechanochromic sensors have been largely fabricated and studied with periodic structures such as surface relief patterns and photonic crystals. Although periodic structures can provide high wavelength selectivity, the strong viewing-angle-dependence of the color hinders their practical application in indoor and outdoor environments. Herein, a Fabry–Perot (F–P) interferometer composed of an elastomeric triblock copolymer as a dielectric spacer sandwiched between two metal layers is presented as an angle-insensitive mechanochromic sensor. The planar structure of this device, formed on a flexible substrate, can be stretched to strains greater than 100%, and it reveals diverse colors according to the applied strain. The revealed colors are highly independent of the viewing angle, as confirmed both experimentally and theoretically. The developed sensor can be attached to any material including metals to visually detect mechanical failures (cracking, cleavage, and deformation) of the material. Therefore, this F–P mechanochromic sensor shows significant potential for real-time structural health monitoring.