scholarly journals A Review of Conductive Hydrogel Used in Flexible Strain Sensor

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 3947 ◽  
Author(s):  
Li Tang ◽  
Shaoji Wu ◽  
Jie Qu ◽  
Liang Gong ◽  
Jianxin Tang
Keyword(s):  
Chemical Properties ◽  
Soft Materials ◽  
Strain Sensors ◽  
Synthetic Methods ◽  
Self Healing ◽  
Ionic Conductors ◽  
Conductive Hydrogel ◽  
Strong Adhesion ◽  
Flexible Strain Sensor ◽  
Conductive Hydrogels

Hydrogels, as classic soft materials, are important materials for tissue engineering and biosensing with unique properties, such as good biocompatibility, high stretchability, strong adhesion, excellent self-healing, and self-recovery. Conductive hydrogels possess the additional property of conductivity, which endows them with advanced applications in actuating devices, biomedicine, and sensing. In this review, we provide an overview of the recent development of conductive hydrogels in the field of strain sensors, with particular focus on the types of conductive fillers, including ionic conductors, conducting nanomaterials, and conductive polymers. The synthetic methods of such conductive hydrogel materials and their physical and chemical properties are highlighted. At last, challenges and future perspectives of conductive hydrogels applied in flexible strain sensors are discussed.

Highly stretchable, self-adhesive, biocompatible, conductive hydrogels as fully polymeric strain sensors

2020 ◽  
Vol 8 (39) ◽  
pp. 20474-20485
Author(s):  
Dong Zhang ◽  
Yijing Tang ◽  
Yanxian Zhang ◽  
Fengyu Yang ◽  
Yonglan Liu ◽  
...  
Keyword(s):  
Strain Sensors ◽  
Surface Adhesion ◽  
Human Movements ◽  
Conductive Hydrogel ◽  
Highly Stretchable ◽  
Strong Surface ◽  
Conductive Hydrogels

A new fully polymeric conductive hydrogel sensor with IPN structure was developed, which achieved ultra-high stretchability, strong surface adhesion, and high sensing stability in response to both large and subtle human movements.

Stretchable and tough conductive hydrogels for flexible pressure and strain sensors

2020 ◽  
Vol 8 (16) ◽  
pp. 3437-3459 ◽  
Author(s):  
Zhenwu Wang ◽  
Yang Cong ◽  
Jun Fu
Keyword(s):  
Implantable Devices ◽  
Strain Sensors ◽  
Recent Advances ◽  
Conductive Hydrogel ◽  
Conductive Hydrogels

This review summarises recent advances in stretchable and tough conductive hydrogel sensors for wearable and implantable devices.

scholarly journals Highly Stretchable and Self-Healing Strain Sensors Based on Nanocellulose-Supported Graphene Dispersed in Electro-Conductive Hydrogels

Nanomaterials ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 937 ◽  
Author(s):  
Chunxiao Zheng ◽  
Yiying Yue ◽  
Lu Gan ◽  
Xinwu Xu ◽  
Changtong Mei ◽  
...  
Keyword(s):  
Vinyl Alcohol ◽  
Cellulose Nanofibers ◽  
Strain Sensors ◽  
Gauge Factor ◽  
Poly Vinyl Alcohol ◽  
Self Healing ◽  
Composite Gels ◽  
Highly Stretchable ◽  
Conductive Hydrogels ◽  
Pva Hydrogel

Intrinsic self-healing and highly stretchable electro-conductive hydrogels demonstrate wide-ranging utilization in intelligent electronic skin. Herein, we propose a new class of strain sensors prepared by cellulose nanofibers (CNFs) and graphene (GN) co-incorporated poly (vinyl alcohol)-borax (GN-CNF@PVA) hydrogel. The borax can reversibly and dynamically associate with poly (vinyl alcohol) (PVA) and GN-CNF nanocomplexes as a cross-linking agent, providing a tough and flexible network with the hydrogels. CNFs act as a bio-template and dispersant to support GN to create homogeneous GN-CNF aqueous dispersion, endowing the GN-CNF@PVA gels with promoted mechanical flexibility, strength and good conductivity. The resulting composite gels have high stretchability (break-up elongation up to 1000%), excellent viscoelasticity (storage modulus up to 3.7 kPa), rapid self-healing ability (20 s) and high healing efficiency (97.7 ± 1.2%). Due to effective electric pathways provided by GN-CNF nanocomplexes, the strain sensors integrated by GN-CNF@PVA hydrogel with good responsiveness, stability and repeatability can efficiently identify and monitor the various human motions with the gauge factor (GF) of about 3.8, showing promising applications in the field of wearable sensing devices.

scholarly journals Ultrasensitive Wearable Strain Sensors of 3D Printing Tough and Conductive Hydrogels

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1873 ◽  
Author(s):  
Jilong Wang ◽  
Yan Liu ◽  
Siheng Su ◽  
Junhua Wei ◽  
Syed Rahman ◽  
...  
Keyword(s):  
3D Printing ◽  
Calcium Ions ◽  
Strain Sensors ◽  
Wearable Electronics ◽  
Ionic Conductors ◽  
Hydrogel Film ◽  
Excess Calcium ◽  
3D Printed ◽  
Conductive Hydrogels ◽  
Human Motions

In this study, tough and conductive hydrogels were printed by 3D printing method. The combination of thermo-responsive agar and ionic-responsive alginate can highly improve the shape fidelity. With addition of agar, ink viscosity was enhanced, further improving its rheological characteristics for a precise printing. After printing, the printed construct was cured via free radical polymerization, and alginate was crosslinked by calcium ions. Most importantly, with calcium crosslinking of alginate, mechanical properties of 3D printed hydrogels are greatly improved. Furthermore, these 3D printed hydrogels can serve as ionic conductors, because hydrogels contain large amounts of water that dissolve excess calcium ions. A wearable resistive strain sensor that can quickly and precisely detect human motions like finger bending was fabricated by a 3D printed hydrogel film. These results demonstrate that the conductive, transparent, and stretchable hydrogels are promising candidates as soft wearable electronics for healthcare, robotics and entertainment.

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 Dynamic Nanohybrid-Polysaccharide Hydrogels for Soft Wearable Strain Sensing

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3574
Author(s):  
Pejman Heidarian ◽  
Hossein Yousefi ◽  
Akif Kaynak ◽  
Mariana Paulino ◽  
Saleh Gharaie ◽  
...  
Keyword(s):  
Mechanical Strength ◽  
Strain Sensors ◽  
Self Healing ◽  
Nano Materials ◽  
Strain Sensing ◽  
Ferric Ions ◽  
Research Activity ◽  
Adhesion Properties ◽  
High Mechanical Strength ◽  
The Moment

Electroconductive hydrogels with stimuli-free self-healing and self-recovery (SELF) properties and high mechanical strength for wearable strain sensors is an area of intensive research activity at the moment. Most electroconductive hydrogels, however, consist of static bonds for mechanical strength and dynamic bonds for SELF performance, presenting a challenge to improve both properties into one single hydrogel. An alternative strategy to successfully incorporate both properties into one system is via the use of stiff or rigid, yet dynamic nano-materials. In this work, a nano-hybrid modifier derived from nano-chitin coated with ferric ions and tannic acid (TA/Fe@ChNFs) is blended into a starch/polyvinyl alcohol/polyacrylic acid (St/PVA/PAA) hydrogel. It is hypothesized that the TA/Fe@ChNFs nanohybrid imparts both mechanical strength and stimuli-free SELF properties to the hydrogel via dynamic catecholato-metal coordination bonds. Additionally, the catechol groups of TA provide mussel-inspired adhesion properties to the hydrogel. Due to its electroconductivity, toughness, stimuli-free SELF properties, and self-adhesiveness, a prototype soft wearable strain sensor is created using this hydrogel and subsequently tested.

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