A semi-permanent and durable nanoscale-crack-based sensor by on-demand healing

Abstract

Although sensitivity and durability are desirable in a sensor, both of them cannot be easily achieved. Site-specific and effective signal acquisition on the limited area of a sensor inevitably allows fatigue accumulation and contamination. For example, an ultrasensitive nanoscale-crack-based sensor for detecting a mechanical stimulus with tremendous sensitivity (a gauge factor greater than 2000 under 2% strain), yet limited durability (up to a few thousand stretching cycles in tensile tests) has been presented previously. Herein, we suggest a simple yet robust nanoscale-crack-based sensor that achieves remarkable durability through the use of a self-healable polymer. The self-healable polymer helps the crack gap recover and maintain high stability for 1 million cycles under 2% strain. Moreover, site-specific recovery with infrared light irradiation was demonstrated with monolithic arrayed sensors. The proposed strategy provides a unique solution to achieving highly enhanced durability and high mechanosensitivity, which are typically incompatible.

Mimicking Human and Biological Skins for Multifunctional Skin Electronics

“…Despite the ultrahigh sensitivity, an issue with the nanoscale crack sensor is that it is not very durable under repetitive deformations. To overcome this limitation, self‐healable polymers can be applied to the cracked layer . The self‐healable polymer integrated on the crack sensor can recover gaps between nanoscale cracks by self‐healing, thereby providing robust durability.…”

Strain‐Visualization with Ultrasensitive Nanoscale Crack‐Based Sensor Assembled with Hierarchical Thermochromic Membrane

“…The cracks show zipper‐like behavior against even 2% strain or less, and allow high signal‐to‐noise ratio and exceptional sensitivity, a 13 000 gauge factor at 2% strain. More details are shown in prepublished papers . To apply a strain‐visualizing function to the nanoscale crack‐based sensor, the thermochromic membrane that has thermoresponsive, colorimetric function is integrated.…”

“…Figure b represents the mechanism of the strain‐visualization. As presented in resistive sensors, the nanoscale crack‐based sensor could continuously measure resistance variation by mechanical stimulus, such as strain. The resistance would increase dramatically, leading to the joule heating behavior by the mechanism of the working principle in the nanoscale crack‐based sensor.…”

Polyimide Encapsulation of Spider-Inspired Crack-Based Sensors for Durability Improvement

“…When a crack penetrates into the substrate, sensitivity increases by deepening the crack depth [16]. However, repetitive straining accumulates residual stress on the crack vertex, disturbing closing of the crack gap, causing the gauge factor to decrease [37]. Third, the crack sensor on PI substrate with the encapsulating layer had lower sensitivity than that of the crack sensor on PI substrate without encapsulation, but sensitivity drop with repeated tensile load improved slightly.…”