scholarly journals A Skin-Inspired Stretchable, Self-Healing and Electro-Conductive Hydrogel with a Synergistic Triple Network for Wearable Strain Sensors Applied in Human-Motion Detection

Nanomaterials ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1737 ◽  
Author(s):  
Yuanyuan Chen ◽  
Kaiyue Lu ◽  
Yuhan Song ◽  
Jingquan Han ◽  
Yiying Yue ◽  
...  
Keyword(s):  
Polyacrylic Acid ◽  
Cellulose Nanofibrils ◽  
Human Motion ◽  
Strain Sensors ◽  
Current Response ◽  
Oxidized Cellulose ◽  
Self Healing ◽  
Wearable Electronics ◽  
Conductive Hydrogel ◽  
Hydrogel Matrix

Hydrogel-based strain sensors inspired by nature have attracted tremendous attention for their promising applications in advanced wearable electronics. Nevertheless, achieving a skin-like stretchable conductive hydrogel with synergistic characteristics, such as ideal stretchability, excellent sensing performance and high self-healing efficiency, remains challenging. Herein, a highly stretchable, self-healing and electro-conductive hydrogel with a hierarchically triple-network structure was developed through a facile two-step preparation process. Firstly, 2, 2, 6, 6-tetrametylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils were homogeneously dispersed into polyacrylic acid hydrogel, with the presence of ferric ions as an ionic crosslinker to synthesize TEMPO-oxidized cellulose nanofibrils/polyacrylic acid hydrogel via a one-pot free radical polymerization. A polypyrrole conductive network was then incorporated into the synthetic hydrogel matrix as the third-level gel network by polymerizing pyrrole monomers. The hierarchical 3D network was mutually interlocked through hydrogen bonds, ionic coordination interactions and physical entanglements of polymer chains to achieve the target composite hydrogels with a homogeneous texture, enhanced mechanical stretchability (elongation at break of ~890%), high viscoelasticity (maximum storage modulus of ~27.1 kPa), intrinsic self-healing ability (electrical and mechanical healing efficiencies of ~99.4% and 98.3%) and ideal electro-conductibility (~3.9 S m−1). The strain sensor assembled by the hybrid hydrogel, with a desired gauge factor of ~7.3, exhibits a sensitive, fast and stable current response for monitoring small/large-scale human movements in real-time, demonstrating promising applications in damage-free wearable electronics.

scholarly journals Highly Viscoelastic, Stretchable, Conductive, and Self-Healing Strain Sensors based on Cellulose Nanofibers-Reinforced Polyacrylic Acid Hydrogel

2021 ◽  
Author(s):  
Yue Jiao ◽  
Kaiyue Lu ◽  
Ya Lu ◽  
Yiying Yue ◽  
Xinwu Xu ◽  
...  
Keyword(s):  
Polyacrylic Acid ◽  
Cellulose Nanofibers ◽  
Strain Sensors ◽  
Self Healing ◽  
Wearable Electronics ◽  
Chemically Modified ◽  
Mechanical And Electrical Properties ◽  
Healing Efficiency ◽  
Hydrogel Matrix ◽  
External Stimuli

Abstract Conductive and self-healing hydrogels are among the emerging materials that mimic the human skin and are important due to their probable prospects in soft robots and wearable electronics. However, the mechanical properties of the hydrogel matrix limit their applications. In this study, we developed a physicochemically dual cross-linked chemically modified-cellulose nanofibers-carbon nanotubes/polyacrylic acid (TOCNF-CNTs/PAA) hydrogel. The TOCNFs acted both as a nanofiller and dispersant to increase the mechanical strength of the PAA matrix and break the agglomerates of the CNTs. The final self-healing and conductive TOCNF-CNTs/PAA-0.7 (mass ratio of CNTs to AA) hydrogel with a uniform texture exhibited highly intrinsic stretchability (breaking elongation to ca. 850%), enhanced tensile properties (ca. 59kPa), ideal conductivity (ca. 2.88S·m− 1) and pressure sensitivity. Besides, the composite hydrogels achieved up to approximately 98.36% and 99.99% self-healing efficiency for mechanical and electrical properties, respectively, without any external stimuli. Therefore, the as-designed multi-functional self-healing hydrogels, combined with stretching, sensitivity, and repeatability, possess the ability to monitor human activity and develop multifunctional, advanced, and commercial products such as wearable strain sensors, health monitors, and smart robots.

scholarly journals Anisotropic, Wrinkled, and Crack-Bridging Structure for Ultrasensitive, Highly Selective Multidirectional Strain Sensors

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Heng Zhang ◽  
Dan Liu ◽  
Jeng-Hun Lee ◽  
Haomin Chen ◽  
Eunyoung Kim ◽  
...  
Keyword(s):  
Rational Design ◽  
Full Range ◽  
Human Motion ◽  
Strain Sensors ◽  
Gauge Factor ◽  
Wearable Electronics ◽  
Trade Off ◽  
Human Motion Detection ◽  
Sensing Applications ◽  
Anisotropic Structures

AbstractFlexible multidirectional strain sensors are crucial to accurately determining the complex strain states involved in emerging sensing applications. Although considerable efforts have been made to construct anisotropic structures for improved selective sensing capabilities, existing anisotropic sensors suffer from a trade-off between high sensitivity and high stretchability with acceptable linearity. Here, an ultrasensitive, highly selective multidirectional sensor is developed by rational design of functionally different anisotropic layers. The bilayer sensor consists of an aligned carbon nanotube (CNT) array assembled on top of a periodically wrinkled and cracked CNT–graphene oxide film. The transversely aligned CNT layer bridge the underlying longitudinal microcracks to effectively discourage their propagation even when highly stretched, leading to superior sensitivity with a gauge factor of 287.6 across a broad linear working range of up to 100% strain. The wrinkles generated through a pre-straining/releasing routine in the direction transverse to CNT alignment is responsible for exceptional selectivity of 6.3, to the benefit of accurate detection of loading directions by the multidirectional sensor. This work proposes a unique approach to leveraging the inherent merits of two cross-influential anisotropic structures to resolve the trade-off among sensitivity, selectivity, and stretchability, demonstrating promising applications in full-range, multi-axis human motion detection for wearable electronics and smart robotics.

Highly viscoelastic, stretchable, conductive, and self-healing strain sensors based on cellulose nanofiber-reinforced polyacrylic acid hydrogel

Cellulose ◽  
2021 ◽  
Vol 28 (7) ◽  
pp. 4295-4311
Author(s):  
Yue Jiao ◽  
Kaiyue Lu ◽  
Ya Lu ◽  
Yiying Yue ◽  
Xinwu Xu ◽  
...  
Keyword(s):  
Polyacrylic Acid ◽  
Strain Sensors ◽  
Cellulose Nanofiber ◽  
Self Healing

Low temperature tolerant, ultrasensitive strain sensors based on self-healing hydrogel for self-monitor of human motion

2019 ◽  
Vol 257 ◽  
pp. 116177 ◽  
Author(s):  
Shengping Dai ◽  
Xinghao Hu ◽  
Xiuzhu Xu ◽  
Xiaoting Cao ◽  
Yuewen Chen ◽  
...  
Keyword(s):  
Low Temperature ◽  
Human Motion ◽  
Strain Sensors ◽  
Self Healing

scholarly journals Dynamic Mussel-Inspired Chitin Nanocomposite Hydrogels for Wearable Strain Sensors

Polymers ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1416 ◽  
Author(s):  
Pejman Heidarian ◽  
Abbas Z. Kouzani ◽  
Akif Kaynak ◽  
Ali Zolfagharian ◽  
Hossein Yousefi
Keyword(s):  
Mechanical Properties ◽  
Polyacrylic Acid ◽  
Strain Sensors ◽  
Self Healing ◽  
Network Stability ◽  
Ferric Ions ◽  
Trade Off ◽  
Nanocomposite Hydrogels ◽  
Healing Efficiency ◽  
Hydrogel Network

It is an ongoing challenge to fabricate an electroconductive and tough hydrogel with autonomous self-healing and self-recovery (SELF) for wearable strain sensors. Current electroconductive hydrogels often show a trade-off between static crosslinks for mechanical strength and dynamic crosslinks for SELF properties. In this work, a facile procedure was developed to synthesize a dynamic electroconductive hydrogel with excellent SELF and mechanical properties from starch/polyacrylic acid (St/PAA) by simply loading ferric ions (Fe3+) and tannic acid-coated chitin nanofibers (TA-ChNFs) into the hydrogel network. Based on our findings, the highest toughness was observed for the 1 wt.% TA-ChNF-reinforced hydrogel (1.43 MJ/m3), which is 10.5-fold higher than the unreinforced counterpart. Moreover, the 1 wt.% TA-ChNF-reinforced hydrogel showed the highest resistance against crack propagation and a 96.5% healing efficiency after 40 min. Therefore, it was chosen as the optimized hydrogel to pursue the remaining experiments. Due to its unique SELF performance, network stability, superior mechanical, and self-adhesiveness properties, this hydrogel demonstrates potential for applications in self-wearable strain sensors.

Ultrastretchable and Stable Strain Sensors Based on Antifreezing and Self-Healing Ionic Organohydrogels for Human Motion Monitoring

2019 ◽  
Vol 11 (9) ◽  
pp. 9405-9414 ◽  
Author(s):  
Jin Wu ◽  
Zixuan Wu ◽  
Xing Lu ◽  
Songjia Han ◽  
Bo-Ru Yang ◽  
...  
Keyword(s):  
Human Motion ◽  
Strain Sensors ◽  
Self Healing ◽  
Human Motion Monitoring

scholarly journals Extremely Stretchable Strain Sensors Based on Conductive Self-Healing Dynamic Cross-Links Hydrogels for Human-Motion Detection

2016 ◽  
Vol 4 (2) ◽  
pp. 1600190 ◽  
Author(s):  
Guofa Cai ◽  
Jiangxin Wang ◽  
Kai Qian ◽  
Jingwei Chen ◽  
Shaohui Li ◽  
...  
Keyword(s):  
Motion Detection ◽  
Human Motion ◽  
Strain Sensors ◽  
Self Healing ◽  
Human Motion Detection ◽  
Cross Links

scholarly journals Highly Sensitive and Stretchable c-MWCNTs/PPy Embedded Multidirectional Strain Sensor Based on Double Elastic Fabric for Human Motion Detection

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2333
Author(s):  
Huiying Shen ◽  
Huizhen Ke ◽  
Jingdong Feng ◽  
Chenyu Jiang ◽  
Qufu Wei ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Large Scale ◽  
Strain Sensor ◽  
High Sensitivity ◽  
Human Motion ◽  
Strain Sensors ◽  
Gauge Factor ◽  
Wearable Electronics ◽  
Synovial Joint ◽  
Human Motion Detection

Owing to the multi-dimensional complexity of human motions, traditional uniaxial strain sensors lack the accuracy in monitoring dynamic body motions working in different directions, thus multidirectional strain sensors with excellent electromechanical performance are urgently in need. Towards this goal, in this work, a stretchable biaxial strain sensor based on double elastic fabric (DEF) was developed by incorporating carboxylic multi-walled carbon nanotubes(c-MWCNTs) and polypyrrole (PPy) into fabric through simple, scalable soaking and adsorption-oxidizing methods. The fabricated DEF/c-MWCNTs/PPy strain sensor exhibited outstanding anisotropic strain sensing performance, including relatively high sensitivity with the maximum gauge factor (GF) of 5.2, good stretchability of over 80%, fast response time < 100 ms, favorable electromechanical stability, and durability for over 800 stretching–releasing cycles. Moreover, applications of DEF/c-MWCNTs/PPy strain sensor for wearable devices were also reported, which were used for detecting human subtle motions and dynamic large-scale motions. The unconventional applications of DEF/c-MWCNTs/PPy strain sensor were also demonstrated by monitoring complex multi-degrees-of-freedom synovial joint motions of human body, such as neck and shoulder movements, suggesting that such materials showed a great potential to be applied in wearable electronics and personal healthcare monitoring.

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