Mechanochromic Stretchable Electronics

Abstract

Soft and stretchable electronics are promising for a variety of applications such as wearable electronics, human-machine interfaces, and soft robotics. These devices, which are often encased in elastomeric materials, maintain or adjust their functionality during deformation, but can fail catastrophically if extended too far. Here, we report new functional composites in which stretchable electronic properties are coupled to molecular mechanochromic function, enabling at-a-glance visual cues that inform user control. These properties are realized by covalently incorporating a spiropyran mechanophore within poly(dimethylsiloxane) to indicate with a visible color change that a strain threshold has been reached. The resulting colorimetric elastomers can be molded and patterned so that, for example, the word "STOP" appears when a critical strain is reached, indicating to the user that further strain risks device failure. We also show that the strain at color onset can be controlled by layering silicones with different moduli into a composite. As a demonstration, we show how color onset can be tailored to indicate a when a specified frequency of a stretchable liquid metal antenna has been reached. The multiscale combination of mechanochromism and soft electronics offers a new avenue to empower user control of strain-dependent properties for future stretchable devices.

Liquid Metal–Based Soft Microfluidics

“…b) SP‐PDMS liquid metal wire gradually changes color under tension until it breaks. Reproduced with permission . Copyright 2018, American Chemical Society.…”

“…[78] Small 2020, 16,1903841 Reproduced with permission. [73] Copyright 2018, American Chemical Society. c) Liquid metal dynamic contact angle measurements on surfaces of NeverWet.…”

Bio‐inspired Design and Additive Manufacturing of Soft Materials, Machines, Robots, and Haptic Interfaces

“…[121] By linking this compound to ap olymer network, the macroscopic force can be transferred to the molecular scale,w hich imparts reversible color changes to entropically elastic soft robots (Figure 2e). [122,123] Thes ame force can also be generated electrically for fluorescent patterning. [124] Synthetic soft display and camouflage materials inspired by natural organisms,e specially those from animalia, have shown more capabilities than those found in nature.Recently, materials that demonstrate autonomous color-changing behaviors when triggered by multiple environmental stimuli have been developed.…”

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

“…Therefore, the visualization of stimulus by sensors has taken charge of various delicate fields, such as medical devices, including cancer growth monitoring, and heart rate monitoring for patients, and safety devices, including the detection of cracks on pipes, and detection of the failure/explosion of mobile batteries . Recently, mechanosensors that visually display minute mechanical signals have faced huge demand, due to their eidetic readability without signal processing . With the demand, the chromic‐based color‐metric sensor can be considered to realize this concept very easily, showing multiple colors without huge equipment or electrical signal processing …”