A flexible and sensitive strain sensor with three-dimensional reticular structure using biomass Juncus effusus for monitoring human motions

Chang

ACS Appl. Mater. Interfaces

et al. 2022

Integrating structural anisotropy, excellent mechanical properties, and superior sensing capability into conductive hydrogels is of great importance to wearable flexible electronics yet challenging. Herein, inspired from the aligned structure of human muscle, we proposed a facile and universal method to construct an anisotropic hydrogel composed of polyacrylamide and sodium alginate by pre-stretching in a confined geometry and subsequent ionic cross-linking. The designed hydrogels showed extraordinary mechanical performances, such as ultrahigh stretchability, a comparable modulus to that of human tissues, and good toughness, ascribed to their anisotropically aligned polymer networks. Additionally, the hydrogel possessed anisotropic conductivity due to the anisotropy in ion transport channels. The hydrogel along the vertical direction was further cut and assembled into a flexible strain sensor, exhibiting a low detection limit (0.1%), wide strain range (1585%), rapid response (123 ms), distinct resilience, good stability, and repeatability, thereby being capable of monitoring and discriminating different human movements. In addition, the relatively high ionic conductivity and superior sensitivity enabled the anisotropic hydrogel sensor to be used for wireless human–machine interaction. More interestingly, the Ca2+-cross-linking strategy also endowed the hydrogel sensor with antifreezing ability, further broadening their working temperature. This work is expected to speed up the development of hydrogel sensors in the emerging wearable soft electronics.

Section: Resultsmentioning

confidence: 99%

Ultrastretchable, Antifreezing, and High-Performance Strain Sensor Based on a Muscle-Inspired Anisotropic Conductive Hydrogel for Human Motion Monitoring and Wireless Transmission

Chang

ACS Appl. Mater. Interfaces

et al. 2022

ACS Appl. Mater. Interfaces

“…Wang et al proposed a hydrogel with macropores prepared by embedding HEC in polyvinyl alcohol, which can sense the strain below 400% . Flexible substrates include elastic substrates − (polydimethylsiloxane, polyurethane), paper substrates , (fiber mats, paper), fabric substrates , (nonwoven fabrics, nylon), gel substrates ,, (polyvinyl alcohol, polyacrylic acid), etc. Polydimethylsiloxane has good biocompatibility and can fit well with human skin.…”

Section: Introductionmentioning

confidence: 99%

In Situ Polymerized MXene/Polypyrrole/Hydroxyethyl Cellulose-Based Flexible Strain Sensor Enabled by Machine Learning for Handwriting Recognition

Yang

Zhang

Wang

et al. 2023

Flexible strain sensors have significant progress in the fields of human–computer interaction, medical monitoring, and handwriting recognition, but they also face many challenges such as the capture of weak signals, comprehensive acquisition of the information, and accurate recognition. Flexible strain sensors can sense externally applied deformations, accurately measure human motion and physiological signals, and record signal characteristics of handwritten text. Herein, we prepare a sandwich-structured flexible strain sensor based on an MXene/polypyrrole/hydroxyethyl cellulose (MXene/PPy/HEC) conductive material and a PDMS flexible substrate. The sensor features a wide linear strain detection range (0–94%), high sensitivity (gauge factor 357.5), reliable repeatability (>1300 cycles), ultrafast response–recovery time (300 ms), and other excellent sensing properties. The MXene/PPy/HEC sensor can detect human physiological activities, exhibiting excellent performance in measuring external strain changes and real-time motion detection. In addition, the signals of English words, Arabic numerals, and Chinese characters handwritten by volunteers measured by the MXene/PPy/HEC sensor have unique characteristics. Through machine learning technology, different handwritten characters are successfully identified, and the recognition accuracy is higher than 96%. The results show that the MXene/PPy/HEC sensor has a significant impact in the fields of human motion detection, medical and health monitoring, and handwriting recognition.

“…Currently, the materials used in the manufacture of flexible sensors mainly include self-conductive materials, composite conductive materials, and biomass materials. [24][25][26][27][28][29] The challenge is that conductive materials are not usually flexible enough, and the materials with good flexibility normally lack conductivity. Therefore, it is crucial to balance the conductivity and flexibility of materials for making a flexible sensor; as a result, the design and additive manufacturing techniques of composite materials with enhanced conductivity and flexibility have received extensive attention.…”

Section: Introductionmentioning

confidence: 99%

Recent advances in the material design for intelligent wearable devices

Ye³

et al. 2023

Mater. Chem. Front.