Novel Uracil-Functionalized Poly(ionic liquid) Hydrogel: Highly Stretchable and Sensitive as a Direct Wearable Ionic Skin for Human Motion Detection

Abstract

Conductive hydrogel-based ionic skins have attracted immense attention due to their great application prospects in wearable electronic devices. However, simultaneously achieving a combination of a single hydrogel system and excellent comprehensive performance (i.e., mechanical durability, electrical sensitivity, broad-spectrum antibacterial activity, and biocompatibility) remains a challenge. Thus, a novel poly(ionic liquid) hydrogel consisting of poly(acrylamide-co-lauryl methacrylate-co-methyl-uracil-imidazolium chloride-co-2-acryloylamino-2-methyl-1-propane sulfonic acid) (AAm-LMA-MUI-AMPS) was prepared by a micellar copolymerization method. Herein, MUI serves as a supramolecular crosslinker and conductive and bacteriostatic components. Owing to the multiple supramolecular crosslinks and hydrophobic association in the network, the hydrogel exhibits excellent mechanical properties (624 kPa of breaking stress and 1243 kPa of compression stress), skin-like modulus (46.2 kPa), stretchability (1803%), and mechanical durability (200 cycles under 500% strain can be completely recovered). Moreover, with the coordinated combination of each monomer, the hydrogel exhibits the unique advantage of high conductivity (up to 59.34 mS/cm). Hence, the hydrogel was further assembled as an ionic skin sensor, which exhibited a gauge factor (GF) of 10.74 and 7.27 with and without LiCl over a broad strain range (1–1000%), respectively. Furthermore, the hydrogel sensor could monitor human movement in different strain ranges, including body movement and vocal cord vibration. In addition, the antibacterial activity and biocompatibility of the hydrogel sensor were investigated. These findings present a new strategy for the design of new-generation wearable devices with multiple functions.

Ultrastretchable, Highly Conductive, Rapid Self-Recovery, and Antiswelling Hydrogels as Multifunctional Wearable Electronic Devices

“…Further, the tensile strain and stress of the reported conductive hydrogels and CPAL hydrogels are compared in Figure i. The CPAL hydrogels possessed an advantage at the tensile strain and stress levels. − …”

“…(d–h) Mechanical properties of CPAL hydrogels adjusted by changing AlCl 3 content. (i) Ashby plots of tensile stress and tensile strain values of reported hydrogels and the CPAL hydrogel. − …”

Advanced research and prospects on polymer ionic liquids: trends, potential and application

“…A novel PIL hydrogel with high extensibility, mechanical strength, electrical conductivity, and antibacterial and biocompatible properties was obtained. 17 This material (Fig. 6) has high elasticity and sensitivity as a directly wearable ionic skin for human motion detection.…”

Highly stretchable, supersensitive, and self-adhesive ionohydrogels using waterborne polyurethane micelles as cross-linkers for wireless strain sensors

“…Yang et al utilized amphiphilic triblock copolymer micelles (F-127) as a non-covalent cross-linking agent to create an ionogel with an elongation at break of approximately 460%, a breaking strength of approximately 240 kPa, and a breaking toughness of approximately 660 kJ m À3 . [41][42][43] Polyurethanes have been used as an important synthetic material in the preparation of micelles due to their excellent mechanical properties and good designability.…”