Highly Stretchable and Self-Healing “Solid–Liquid” Elastomer with Strain-Rate Sensing Capability

Abstract

To mimic the velocity-sensitive ability of the human skin, we fabricate a class of “solid–liquid” elastomers (SLEs) by interpenetrating polyborosiloxane (PBS) with polydimethylsiloxane (PDMS). PBS forms a dynamic network through boron/oxygen dative bonds, while PDMS is covalently cross-linked to form a permanent network. The permanent network affords a scaffold for the dynamic network, endowing SLEs with high elasticity and structural stability, thereby overcoming the inherent drawbacks such as fluidity and irreversible deformation of conventional solid–liquid materials. Meanwhile, the dissociation and association of the dynamic network is time-dependent. Thus, the modulus of SLEs varies with strain rates, and if the SLEs contain carbon nanotubes, their electric conductivity is also responsive to strain rates. This property can be utilized to fabricate skin-like sensors with the ability to distinguish different contact velocities. Moreover, the dynamic network can dissipate energy and be repaired, leading to the high stretchability and self-healing performance of SLEs.

Stretchable Electronics Based on PDMS Substrates

“…b 3 ) Reproduced with permission. [ 161 ] Copyright 2019, American Society of Chemistry. c 1 ) Self‐healing mechanism of PDMS–PU film.…”

“…[ 157,158 ] However, PBS has not been exploited to fabricate intrinsic velocity‐sensitive materials or sensors owing to its unsatisfactory stretching performance. Various approaches, such as multiwalled CNT‐reinforced PBS nanocomposites and PBS double‐network nanocomposites (Figure 11b), [ 159–161 ] have been reported to equip PBS nanocomposites with high stretchability, self‐healing, and strain‐rate responsive abilities. However, the unfavorable tensile property (<1 MPa) remains a limitation of PBS‐based electronics.…”

A Degradable and Self-Healable Vitrimer Based on Non-isocyanate Polyurethane

“…The yield stress strikingly with increasing strain rate, and meanwhile the Young's modulus obtained from the initial linear region of the stress-strain curves increases from 1.04 to 4.64 MPa in Figure 3D. Such a phenomenon demonstrates that the elastomers possess a selfstiffening ability with increasing strain rate (Wu et al, 2019).…”

Piezoresistive Elastomer-Based Composite Strain Sensors and Their Applications

“…13 Especially strain sensors are linked with devices that measure/detect the pulse, respiration, and/or blood pressure. 130 These continuous measurements allow the health professionals to make an accurate diagnosis and alert for possibly dangerous conditions that are linked with abnormalities in the vital signs. 131 A soft strain sensor based on PDMS and metallic nanofillers was able to detect breath rate and cardiac pulse in the form of an apex cardiogram.…”