Strain-ultrasensitive surface wrinkles for visual wearable optical sensor

Abstract Wearable tactile sensors have found widespread applications in human health monitoring, motion monitoring, human-machine interaction, and artificial prostheses. Herein, we demonstrate a new and feasible strategy for wearable optical sensors based on surface wrinkles ultrasensitive to strain using a bilayer wrinkling system, in which the sensing mechanism is different from that of the traditional electrical sensors. The strain (\(\overrightarrow{S}\left(\epsilon , {\theta }_{S}\right)\)), the wrinkled topography (\(\overrightarrow{W}\left(A, {\theta }_{W}\right)\)), and the reflected optical signal (\(\overrightarrow{O}\left(\delta , {\theta }_{O}\right)\)) functions are correlated with each other, allowing simultaneous measurement of strain magnitude and direction due to the vector property of optical signals. In addition, interactively visualized detection of slight strain has been achieved by conspicuous structural color change, successfully amplifying the strain signal owing to the ultra-sensitivity of wrinkles and the nonlinearity of optical signal. The sensor also exhibits electrical safety and immunity to electromagnetic interference, and thus may find potential applications in detecting various complex slight strains, such as subtle human motion or object deformation.