Waterproof, Highly Tough, and Fast Self-Healing Polyurethane for Durable Electronic Skin

Abstract

A stretchable electronic skin (e-skin) requires a durable elastomeric matrix to serve in various conditions. Therefore, excellent and balanced properties such as elasticity, water proof capability, toughness, and self-healing are demanded. However, it is very difficult and often contradictory to optimize them at one time. Here, a polyurethane (BS-PU-3) containing a polydisperse hard segment, hydrophobic soft segment, and a dynamic disulfide bond was prepared by one-pot synthesis. Unlike the normal two-pot reaction, BS-PU-3 obtained through the one-pot method owned a higher density of self-healing points along the main chain and a faster self-healing speed, which reached 1.11 μm/min in a cut-through sample and recovered more than 93% of virgin mechanical properties in 6 h at room temperature. Moreover, a remarkable toughness of 27.5 MJ/m3 assures its durability as an e-skin matrix. Even with a 1 mm notch (half of the total width) on a standard dumbbell specimen, it could still bear the tensile strain up to 324% without any crack propagation. With polybutadiene as the soft segment, the shape, microstructure, and conductivity in BS-PU-3 and BS-PU-3-based stretchable electronics kept very stable after soaking in water for 3 days, proving the super waterproof property. An e-skin demo was constructed, and self-healing in pressure sensitivity, mechanical, and electrical properties were verified.

Transparency‐tunable and moderate‐temperature healable thermoplastic polyurethane elastomer based on bisphenol A chain‐extender

“…13 In addition, the soft segments can provide chain mobility, which contributes to attachment of the damaged surfaces, and diffusion and entanglement of the molecular chains, 14,15 so polyurethane is widely used for self-healing materials. [16][17][18] Polyurethane can heal through noncovalent bonds such as hydrogen bonding, 19,20 metal-ligand, 21,22 host-guest, 23 π-π stacking 24 ; van der Waals interaction, 25 and interdiffusion, 26 also heal through dynamic covalent bonds such as Diels-Alder reaction, 27,28 disulfide, 29,30 diselenide, 31 ditelluride, 32 imine, 33 hindered urea, 34 or oxime-carbamate. 35 However, the relationship among transparency, self-healing, and structure of polymers needs to be further explored.…”

Ultrarobust, tough and highly stretchable self-healing materials based on cartilage-inspired noncovalent assembly nanostructure

“…4) gradually shift to 3321 cm -1 . Besides, the intensity of 3326 cm -1 related to hydrogen bonded -NH groups in PU 49 gradually decreases, while that of the bands at 3458, and 3430 cm -1 gradually increases. These spectral features indicate that the hydrogen bonding between PU and TA-modified WS2 gradually broken with the increasing temperature.…”

Water‐soluble polyurethane/CaCO3 composites for gunpowder storage

“…[11,[15][16][17][18][19][20] These days, eco-friendly research works are gaining huge importance due to the depletion of fossil fuels and increases in global warming. [21][22][23][24][25][26][27][28][29][30] Wu et al [31] fabricated water-soluble polyurethane carbon nanotube composites by an in situ polymerization process. They studied the structure, mechanical and electrical properties, and morphological appearance of the WSPU composites.…”

“…[ 11,15–20 ] These days, eco‐friendly research works are gaining huge importance due to the depletion of fossil fuels and increases in global warming. [ 21–30 ]…”

“…Further, Xu et al [ 33 ] developed chitosan nanoparticles‐coated biocompatible water‐soluble polyurethane composites and deduced that they had produced films with good mechanical properties. In addition, polyurethane can be applied in self‐healing for durable electronic skin as proposed by Wu et al [ 22 ] They demonstrated a hydrophobic soft segment and polydisperse hard segment and obtained higher density and self‐healing materials.…”