A flexible, adhesive and self-healable hydrogel-based wearable strain sensor for human motion and physiological signal monitoring

Xia, Shan; Song, Shixin; Jia, Fei; Gao, Guanghui

doi:10.1039/c9tb01039d

Cited by 275 publications

(196 citation statements)

References 40 publications

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“…[ 16 ] Nevertheless, the results show that PVA/AgNWs sensor has an excellent durability up to 2000 cycles, comparable to a previous report. [ 38 ] The remarkably stable performance of present sensor confirms its high potential for practical applications such as wearable sensors for long‐term monitoring.…”

Section: Resultsmentioning

confidence: 60%

“…Stretching increases the distance between nanowires and reduces the overlapping between them, which results in higher resistance (Figure 1B). [ 16,38,39 ]…”

Section: Resultsmentioning

confidence: 99%

“…This slight drift may be attributed to the evaporation of water in the hydrogel‐based sensors. [ 16,17,38 ] In addition, the small hysteresis of the sensor, as discussed later, could also lead to the signal drift. [ 16 ] Nevertheless, the results show that PVA/AgNWs sensor has an excellent durability up to 2000 cycles, comparable to a previous report.…”

Section: Resultsmentioning

confidence: 99%

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Biocompatible and Highly Stretchable PVA/AgNWs Hydrogel Strain Sensors for Human Motion Detection

Azadi

Peng

Moshizi

et al. 2020

Adv Materials Technologies

113

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Hydrogel‐based strain sensors have attracted considerable interest for applications such as skin‐like electronics for human motion detection, soft robotics, and human–machine interfaces. However, fabrication of hydrogel strain sensors with desirable mechanical and piezoresistive properties is still challenging. Herein, a biocompatible hydrogel sensor is presented, which is made of polyvinyl alcohol (PVA) nanocomposite with high stretchability up to 500% strain, high mechanical strength of 900 kPa, and electrical conductivity (1.85 S m‐1) comparable to human skin. The hydrogel sensors demonstrate excellent linearity in the whole detection range and great durability under cyclic loading with low hysteresis of 7%. These excellent properties are believed to be contributed by a new bilayer structural design, i.e., a thin, conductive hybrid layer of PVA/silver nanowires (AgNWs) deposited on a pure strong PVA substrate. PVA solution of high concentration is used to fabricate the substrate while the top layer consists of dilute PVA solution so that high content of AgNWs can be dispersed to achieve high electrical conductivity. Together with a rapid response time (0.32 s) and biocompatibility, this new sensor offers great potential as a wearable sensor for epidermal sensing applications, e.g., detecting human joint and muscle movements.

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Section: Resultsmentioning

confidence: 60%

“…Stretching increases the distance between nanowires and reduces the overlapping between them, which results in higher resistance (Figure 1B). [ 16,38,39 ]…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Biocompatible and Highly Stretchable PVA/AgNWs Hydrogel Strain Sensors for Human Motion Detection

Azadi

Peng

Moshizi

et al. 2020

Adv Materials Technologies

113

View full text Add to dashboard Cite

show abstract

“…To this end, researchers modified the surface of CNTs for fabricating conductive hydrogel, including carboxyl functionalization, amino functionalization or organic molecular modification. Gao group reported a carboxyl-functionalized multi-walled carbon nanotube (c-MWCNTs) crosslinked chemical-physical hybrid hydrogel [ 63 ]. Conductive c-MWCNTs crosslinked chitosan (CS) through dynamic ionic bonds to form physical crosslinked hydrogel.…”

Section: Conducting Nanomaterialsmentioning

confidence: 99%

A Review of Conductive Hydrogel Used in Flexible Strain Sensor

et al. 2020

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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.

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“…In addition, flexible sensors based on this hydrogel can accurately detect large-scale and small-scale human activities, including joint movements, speech, breathing, and even subtle blood pulsations as shown in Figure 7. [113] Similarly, a combination of conductive nanomaterials and conductive polymers results in self-healing conductive hydrogels with very high conductivity. [116] The combination of liquid metals with flexible polymer hydrogels opens a new pathway for the development of highly conductive and stretchable hydrogels with highly sensitive sensors.…”

Section: Conductivity Of Hydrogel Flexible Sensormentioning

confidence: 99%

Flexible Self‐Repairing Materials for Wearable Sensing Applications: Elastomers and Hydrogels

Zhou

Dong

et al. 2020

Macromol. Rapid Commun.

100

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related operations, and destroy the operation of the whole equipment (system). Bao and his colleagues developed a novel self-healing and mechanical force-sensing flexible sensor using micro-structured elastomeric dielectrics, which served as a foundation to improve the stability and lifetime of flexible sensors. [8] Self-healing flexible materials can be divided into two categories, one is solvent-less or water-free after curing and high degree of polymerization of elastomers, such as polyamide, polyurethane, etc., the other is hydrogels, low degree of polymerization, structural cross-linking. In self-healing flexible elastomer sensors, the structure of elastomer is mostly linear structure or semi-cross-linked structure; the elastomer of cross-linked structure is poor flexibility and fragile due to its high degree of polymerization. The elasticity of semi-crosslinked structure has excellent resilience and great potential in the field of flexible flexural sensors. In the past two years, self-healing flexible hydrogels have attracted extensive attention due to their excellent stretchability and resilience, as well as outstanding performance in the preparation of sensors with high sensitivity and fast response. [9,10] Sensors with elastomers and hydrogels as flexible matrices face great difficulties in conductivity, which affects the sensitivity and stability of the sensors. Filling conductive materials is the most commonly method, in which organic conductive polymers (polyaniline, [11] polypyrrole [12]) are filled to construct conductive networks, and good interfacial compatibility results in uniform conductive polymer elastomers, but the inherent color fillers affect the transparency of flexible sensors, limiting their applications in the biomedical field. [13-17] Flexible materials filled with inorganic conductive particles (graphene, nano-silver wire) have high conductivity, but phase separation between filler and matrix usually reduces the tensile, toughness and fatigue resistance, and even affects the self-healing ability of flexible materials. Modified fillers are often required to improve affinity for flexible matrices and inhibit phase separation. However, many hydrogel matrices are intrinsically weak and cannot withstand cyclic loadings. [18] Although surface modified fillers can improve strength and toughness, it is difficult to compensate for the inherent weaknesses. For self-healing flexible elastomers, conductive flexible materials can still be endowed with conductivity by scraping or printing conductive particles on the Flexible pressure and strain sensors have great potential for applications in wearable and implantable devices, soft robots, and artificial skin. The introduction of self-healing performance has made a positive contribution to the lifetime and stability of flexible sensors. At present, many self-healing flexible sensors with high sensitivity have been developed to detect the signal of organism activity. The sensitivity, reliability, and stability of self-healing flexible sensors depend...

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A flexible, adhesive and self-healable hydrogel-based wearable strain sensor for human motion and physiological signal monitoring

Abstract: A flexible and wearable sensor is prepared to monitor human motions such as joint motion, speaking, breathing, and slight blood pulsation.

Cited by 275 publications

References 40 publications

Biocompatible and Highly Stretchable PVA/AgNWs Hydrogel Strain Sensors for Human Motion Detection

Biocompatible and Highly Stretchable PVA/AgNWs Hydrogel Strain Sensors for Human Motion Detection

A Review of Conductive Hydrogel Used in Flexible Strain Sensor

Flexible Self‐Repairing Materials for Wearable Sensing Applications: Elastomers and Hydrogels

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