Highly Stretchable, Elastic, and Sensitive MXene-Based Hydrogel for Flexible Strain and Pressure Sensors

Abstract

Electronic skin is driving the next generation of cutting-edge wearable electronic products due to its good wearability and high accuracy of information acquisition. However, it remains a challenge to fulfill the requirements on detecting full-range human activities with existing flexible strain sensors. Herein, highly stretchable, sensitive, and multifunctional flexible strain sensors based on MXene- (Ti3C2Tx-) composited poly(vinyl alcohol)/polyvinyl pyrrolidone double-network hydrogels were prepared. The uniformly distributed hydrophilic MXene nanosheets formed a three-dimensional conductive network throughout the hydrogel, endowing the flexible sensor with high sensitivity. The strong interaction between the double-network hydrogel matrix and MXene greatly improved the mechanical properties of the hydrogels. The resulting nanocomposited hydrogels featured great tensile performance (2400%), toughness, and resilience. Particularly, the as-prepared flexible pressure sensor revealed ultrahigh sensitivity (10.75 kPa-1) with a wide response range (0-61.5 kPa), fast response (33.5 ms), and low limit of detection (0.87 Pa). Moreover, the hydrogel-based flexible sensors, with high sensitivity and durability, could be employed to monitor full-range human motions and assembled into some aligned devices for subtle pressure detection, providing enormous potential in facial expression and phonation recognition, handwriting verification, healthy diagnosis, and wearable electronics.

Nanocomposite Conductive Bioinks Based on Low-Concentration GelMA and MXene Nanosheets/Gold Nanoparticles Providing Enhanced Printability of Functional Skeletal Muscle Tissues

“…MXene, with its highly conductive properties, was previously implemented in the development of conductive hydrogels such as an MXene-catalyzed poly­(acrylic acid) (PAA) hydrogel, a MXene-hyaluronic acid/alginate hydrogel, and MXene-composited poly­(vinyl alcohol)/poly­(vinyl pyrrolidone) double-network hydrogels. ,, In our study, MXene enhanced the conductivity of low-concentration GelMA to 0.65 ± 0.04 and 0.94 ± 0.12 S/m when 0.05 and 0.1 mg/mL concentrations were used, respectively. Conductivity values achieved by either the addition of AuNPs or MXene were in the range of electrical conductivity of the excitable tissues (0.4–0.9 S/m), which indicates that such hydrogels are biomimetic and of physiological relevance.…”

Thermoresponsive Lignin-Reinforced Poly(Ionic Liquid) Hydrogel Wireless Strain Sensor

“…The hydrogel, with a unique three-dimensional (3D) hydrophilic polymer network, performs high stretchability, exceptional biocompatibility, and degradability, exert broad application prospects in the fields of biological wound dressings, drug delivery, sensors, actuators, and flexible energy storage devices [22][23][24][25][26][27]. Ionic liquids are a group of organic salts comprised of organic cations and organic or inorganic anions [28,29].…”

Wrinkle-Enabled Highly Stretchable Strain Sensors for Wide-Range Health Monitoring with a Big Data Cloud Platform

“…They have wide-range applications for monitoring surface strains of human skin due to joint motion, tissue swelling, wound healing, or even emotional expression. [5][6][7] Different types of flexible strain sensors have been reported. [8][9][10][11] However, practical implementation of these strain sensors for skinmountable and wearable applications still remains a great challenge due to the sophisticated measurement equipment, poor resolution, and/or poor dynamic performance of the senosrs.…”

“…[24][25][26][27][28] For example, Liu Q. et al reported a graphenebased device with a fish-scale microstructure configuration, and achieved a sensing range up to 82% strain, a GF value of 16.2−150 and excellent reliability and stability (>5000 cycles). 24 Lin, L. et al proposed a facile preparation method for superhydrophobic and multi-functional conductive nanofiber composites (CNCs) with a dual conductive network, and the CNCs based strain sensor possesses an extremely large GF value of 1.04×10 5 , with the strain range from 20% to 70%. 25 Li, Q. et al developed strain sensors using ultraviolet/ozone (UV/O3) treated CNT/Ecoflex, and achieved a high sensitivity up to 1020.2 and a stretchability up to 100%.…”

“…The WIoTs will not only continuously monitor the user’s health conditions in real time with a function of long-distance data transmission but also provide timely information of various health parameters to the users and their doctors or physicians. , Flexible strain sensors are regarded as one of the key WIoTs, which can be designed to attach to a targeted flexible object for the purpose of measuring its deformation in a precise manner. They have wide-range applications for monitoring surface strains of human skin due to joint motion, tissue swelling, wound healing, or even emotional expression. − Different types of flexible strain sensors have been reported. − However, practical implementation of these strain sensors for skin-mountable and wearable applications still remains a great challenge because of the sophisticated measurement equipment, poor resolution, and/or poor dynamic performance of the sensors. , Currently, resistive strain sensors are regarded as promising and valuable tools for wearable applications, as they require relatively simple read-out systems and structure design, offer the potentially high flexibility, stretchability, and high sensitivity, and have simple microfabrication processes.…”