Hysteresis-Free Double-Network Hydrogel-Based Strain Sensor for Wearable Smart Bioelectronics

Abstract

Hydrogel-based electronics have attracted substantial attention in the field of biological engineering, energy storage devices, and soft actuators due to their resemblance to living tissues, biocompatibility, tunable softness, and consolidated structures. However, combining the properties of quick resilience, hysteresis-free, and robust mechanical properties in physically cross-linked hydrogels is still a great challenge. Herein, we present a vinyl hybrid silica nanoparticle (VSNPs)/polyacrylamide (PAAm)/alginate double-network hydrogel-based strain sensor with the characteristics of quick resilience, hysteresis-free, and a low limit of detection (LOD). The physical cross-linking among PAAm chains and covalent cross-linking between PAAm, alginate, and N,N-methylenebisacrylamide chains promotes excellent mechanical properties. Moreover, the incorporation of VSNPs reinforces the mechanical strength by the dynamic cross-linking of the PAAm network to maintain the integrity of the hydrogel and works as a stress buffer to dissipate energy. The as-prepared hydrogel-based sensor exhibits a strain sensitivity (i.e., gauge factor) of 1.73 (up to 100% strain), a response time of 0.16 s, an ultra-low electrical hysteresis of 2.43%, and a low LOD of 0.4%. The outstanding properties of the hydrogel are further used to illustrate the utility of the sensor in e-skin, ranging from low-strain applications, such as carotid pulse and artificial sound detection, to large bending applications, such as sign language translations. In addition, an efficient and cost-effective synthesis of double-network hydrogel that can overcome the bottleneck of the electromechanical properties of single network hydrogel has potential prospects in soft actuators, tissue engineering, and various biomedical applications.

A Breathable Knitted Fabric-Based Smart System with Enhanced Superhydrophobicity for Drowning Alarming

“…Δ R / R 0 of the fabricated sample for stretching under different tensile speeds (a) and different strains (b); (c) response time of the sensor during loading and unloading; (d) comparison of the GF value as a function of stretchability with other reported strain sensors; − (e) resistance change under cyclic stretching and releasing for 10 000 s.…”

Bio-Inspired Homogeneous Conductive Hydrogel with Flexibility and Adhesiveness for Information Transmission and Sign Language Recognition

“…In summary, the hydrogel exhibited excellent sensitivity throughout the whole stretching process, indicating that the hydrogel could be used as a flexible strain sensor for both fine amplitude motion and macroscopic deformation sensing. Given the sensing capability of the H-A-CP-3 hydrogel, the hydrogel strain sensor was compared with similar sensing materials previously reported in order to confirm the excellent characteristics in the field of flexible sign language interpreting devices. ,,,− Figure c illustrates the hydrogel in terms of its stretchability, adhesiveness, sensitivity, and responsiveness, exhibiting a skin-like mechanical performance and excellent sensing properties.…”

Ionic Conduction and Dielectric Response of Nanoparticle-Coupled Hydrogel Network Polymer Electrolytes

“…This is consistent with the excellent water retention ability of HPE-NP; i.e., after 12 days, the NP-containing HPEs could retain 93% of its initial water content (Figure S3). These results indicate that this electrolyte has the ability to retain water from −70 °C up to 100 °C and does not evaporate or crystallize, , which could be an advantage of using HPE-NP in wide temperature-tolerant supercapacitors.…”