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 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 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.

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

scholarly journals Room-temperature autonomous self-healing glassy polymers with hyperbranched structure

2020 ◽  
Vol 117 (21) ◽  
pp. 11299-11305 ◽  
Author(s):  
Hao Wang ◽  
Hanchao Liu ◽  
Zhenxing Cao ◽  
Weihang Li ◽  
Xin Huang ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Room Temperature ◽  
Glassy State ◽  
Glassy Polymers ◽  
Self Healing ◽  
External Branch ◽  
Healing Efficiency ◽  
High Degree ◽  
External Stimuli ◽  
Hyperbranched Structure

Glassy polymers are extremely difficult to self-heal below their glass transition temperature (Tg) due to the frozen molecules. Here, we fabricate a series of randomly hyperbranched polymers (RHP) with high density of multiple hydrogen bonds, which showTgup to 49 °C and storage modulus up to 2.7 GPa. We reveal that the hyperbranched structure not only allows the external branch units and terminals of the molecules to have a high degree of mobility in the glassy state, but also leads to the coexistence of “free” and associated complementary moieties of hydrogen bonds. The free complementary moieties can exchange with the associated hydrogen bonds, enabling network reconfiguration in the glassy polymer. As a result, the RHP shows amazing instantaneous self-healing with recovered tensile strength up to 5.5 MPa within 1 min, and the self-healing efficiency increases with contacting time at room temperature without the intervention of external stimuli.

Tough but self-healing and 3D printable hydrogels for E-skin, E-noses and laser controlled actuators

2019 ◽  
Vol 7 (43) ◽  
pp. 24814-24829 ◽  
Author(s):  
Yitian Wang ◽  
Qiang Chang ◽  
Rixing Zhan ◽  
Kaige Xu ◽  
Ying Wang ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Mechanical Strength ◽  
Polyacrylic Acid ◽  
Self Healing ◽  
Healing Efficiency ◽  
Physically Crosslinked

A versatile hydrogel with extraordinary mechanical strength and self-healing efficiency was developed by integrating physically crosslinked graphene oxide into a chemically crosslinked polyacrylic acid network.

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 Highly Stretchable, Elastic, and Sensitive MXene-Based Hydrogel for Flexible Strain and Pressure Sensors

Research ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Yao Lu ◽  
Xinyu Qu ◽  
Wen Zhao ◽  
Yanfang Ren ◽  
Weili Si ◽  
...  
Keyword(s):  
Limit Of Detection ◽  
Full Range ◽  
Pressure Sensors ◽  
High Sensitivity ◽  
Strain Sensors ◽  
Poly Vinyl Alcohol ◽  
Wearable Electronics ◽  
Double Network ◽  
Hydrogel Matrix ◽  
Highly Stretchable

Electronic skin is driving the next generation of cutting-edge wearable electronic products due to its good wearability and high accuracy of information acquisition. However, it remains a challenge to fulfill the requirements on detecting full-range human activities with existing flexible strain sensors. Herein, highly stretchable, sensitive, and multifunctional flexible strain sensors based on MXene- (Ti3C2Tx-) composited poly(vinyl alcohol)/polyvinyl pyrrolidone double-network hydrogels were prepared. The uniformly distributed hydrophilic MXene nanosheets formed a three-dimensional conductive network throughout the hydrogel, endowing the flexible sensor with high sensitivity. The strong interaction between the double-network hydrogel matrix and MXene greatly improved the mechanical properties of the hydrogels. The resulting nanocomposited hydrogels featured great tensile performance (2400%), toughness, and resilience. Particularly, the as-prepared flexible pressure sensor revealed ultrahigh sensitivity (10.75 kPa-1) with a wide response range (0-61.5 kPa), fast response (33.5 ms), and low limit of detection (0.87 Pa). Moreover, the hydrogel-based flexible sensors, with high sensitivity and durability, could be employed to monitor full-range human motions and assembled into some aligned devices for subtle pressure detection, providing enormous potential in facial expression and phonation recognition, handwriting verification, healthy diagnosis, and wearable electronics.

scholarly journals Ultra-Stretchable and Self-Healing Anti-Freezing Strain Sensors Based on Hydrophobic Associated Polyacrylic Acid Hydrogels

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6165
Author(s):  
Shuya Yin ◽  
Gehong Su ◽  
Jiajun Chen ◽  
Xiaoyan Peng ◽  
Tao Zhou
Keyword(s):  
Flexible Electronics ◽  
Polyacrylic Acid ◽  
Retention Rate ◽  
Strain Sensors ◽  
Working Environment ◽  
Glycerol Solution ◽  
Self Healing ◽  
Ambient Conditions ◽  
Subzero Temperatures ◽  
Water Glycerol

Water-rich conductive hydrogels with excellent stretchability are promising in strain sensors due to their potential application in flexible electronics. However, the features of being water-rich also limit their working environment. Hydrogels must be frozen at subzero temperatures and dried out under ambient conditions, leading to a loss of mechanical and electric properties. Herein, we prepare HAGx hydrogels (a polyacrylic acid (HAPAA) hydrogel in a binary water–glycerol solution, where x is the mass ratio of water to glycerol), in which the water is replaced with water–glycerol mixed solutions. The as-prepared HAGx hydrogels show great anti-freezing properties at a range of −70 to 25 °C, as well as excellent moisture stability (the weight retention rate was as high as 93% after 14 days). With the increase of glycerol, HAGx hydrogels demonstrate a superior stretchable and self-healing ability, which could even be stretched to more than 6000% without breaking, and had a 100% self-healing efficiency. The HAGx hydrogels had good self-healing ability at subzero temperatures. In addition, HAGx hydrogels also had eye-catching adhesive properties and transparency, which is helpful when used as strain sensors.

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.

scholarly journals Ultrarobust, tough and highly stretchable self-healing materials based on cartilage-inspired noncovalent assembly nanostructure

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yuyan Wang ◽  
Xin Huang ◽  
Xinxing Zhang
Keyword(s):  
Spider Silk ◽  
Self Healing ◽  
High Toughness ◽  
Healing Efficiency ◽  
Strong Interfacial Interaction ◽  
Highly Stretchable ◽  
Noncovalent Bonds ◽  
Actuation Devices ◽  
Noncovalent Bonding ◽  
Polyurethane Matrix

AbstractSelf-healing materials integrated with excellent mechanical strength and simultaneously high healing efficiency would be of great use in many fields, however their fabrication has been proven extremely challenging. Here, inspired by biological cartilage, we present an ultrarobust self-healing material by incorporating high density noncovalent bonds at the interfaces between the dentritic tannic acid-modified tungsten disulfide nanosheets and polyurethane matrix to collectively produce a strong interfacial interaction. The resultant nanocomposite material with interwoven network shows excellent tensile strength (52.3 MPa), high toughness (282.7 MJ m‒3, which is 1.6 times higher than spider silk and 9.4 times higher than metallic aluminum), high stretchability (1020.8%) and excellent healing efficiency (80–100%), which overturns the previous understanding of traditional noncovalent bonding self-healing materials where high mechanical robustness and healing ability are mutually exclusive. Moreover, the interfacical supramolecular crosslinking structure enables the functional-healing ability of the resultant flexible smart actuation devices. This work opens an avenue toward the development of ultrarobust self-healing materials for various flexible functional devices.

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