Muscle‐Inspired MXene Conductive Hydrogels with Anisotropy and Low‐Temperature Tolerance for Wearable Flexible Sensors and Arrays

Abstract

Conductive hydrogels as flexible electronic devices, not only have unique attractions but also meet the basic need of mechanical flexibility and intelligent sensing. How to endow anisotropy and a wide application temperature range for traditional homogeneous conductive hydrogels and flexible sensors is still a challenge. Herein, a directional freezing method is used to prepare anisotropic MXene conductive hydrogels that are inspired by ordered structures of muscles. Due to the anisotropy of MXene conductive hydrogels, the mechanical properties and electrical conductivity are enhanced in specific directions. The hydrogels have a wide temperature resistance range of −36 to 25 °C through solvent substitution. Thus, the muscle-inspired MXene conductive hydrogels with anisotropy and low-temperature resistance can be used as wearable flexible sensors. The sensing signals are further displayed on the mobile phone as images through wireless technology, and images will change with the collected signals to achieve motion detection. Multiple flexible sensors are also assembled into a 3D sensor array for detecting the magnitude and spatial distribution of forces or strains. The MXene conductive hydrogels with ordered orientation and anisotropy are promising for flexible sensors, which have broad application prospects in human-machine interface compatibility and medical monitoring.

Hydrogels as Soft Ionic Conductors in Flexible and Wearable Triboelectric Nanogenerators

“…Although the conductivity of hydrogels is lower than that of metal electrodes, the internal resistance is still acceptable. For example, when connecting the PVA/MXene hydrogel prepared by Feng et al [53] into a closed circuit, the green LED could be lit up (Figure 3g). Notably, it is found that the internal resistance of many H-TENGs is lower than that of common metal electrode-based TENGs, which may benefit the power circuit management and powering/charging of portable/wearable electronics.…”

“…Reproduced with permission. [ 53 ] Copyright 2021, Wiley‐VCH. h) Output power of the TENG/Ecoflex device versus resistive load.…”

3D Printing of Stretchable, Adhesive and Conductive Ti3C2Tx-Polyacrylic Acid Hydrogels

“…A significant increase in electrical conductivity is attributable to favorably connected Ti 3 C 2 T x nanosheets for an extraordinary electron transport ability [ 37 , 38 ]. Notably, compared to other conductive hydrogels reported previously [ 39 ], our Ti 3 C 2 T x -PAA hydrogel exhibits superior conductivity to most hydrogels so far (see detailed comparison in Table S2 [ 36 , 40 , 41 , 42 , 43 ]). Highly conductive Ti 3 C 2 T x -PAA hydrogel may also be utilized for potential applications in flexible and wearable electronic devices [ 3 , 44 ].…”

“…; Table S1: Compositions of Ti 3 C 2 T x -PAA hydrogels, Table S2: Electrical conductivity comparison of our Ti 3 C 2 T x -PAA hydrogels with previously reported conductive hydrogels. References [ 36 , 40 , 41 , 42 , 43 ] are cited in Supplementary Materials.…”

Wires with Continuous Sabal Leaf‐Patterned Micropores Constructed by Freeze Printing for a Wearable Sensor Responsible to Multiple Deformations

“…[11][12][13][14][15] Depending on the structure design, different deformations of the conductive component, which are stretching, compression, bending and twisting, have been realized. [5][6][7][16][17][18] However, it remains challenging to achieve all these deformations in a single structure design.Among the structural designs, porous structure has the capability to detect tensile, compressive, and torsional strains. [5][6][7]10] Due to the high porosity, porous structures can be largely compressed that they have been widely used to detect compressions.…”