A compliant, self-adhesive and self-healing wearable hydrogel as epidermal strain sensor

Liu, Shuqi; Zheng, Rongmin; Chen, Song; Wu, Yunhui; Liu, Haizhou; Wang, Pingping; Deng, Zhi‐fu; Liu, Lan

doi:10.1039/c8tc00157j

Cited by 174 publications

(152 citation statements)

References 42 publications

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“…More importantly, DA provides a new perspective for the development of wearable strain sensors with excellent self‐adhesive properties. For instance, Liu et al reported a hydrogel‐based self‐adhesive and self‐healing epidermal strain sensor by adding Polydopamine (PDA) to PVA; the developed sensor can detect minute epidermal deformations (0.1% strain) and large body movements (10–75% strain) such as throat vibration and finger bending. In addition, it can be used in the field of low‐intensity strain sensing.…”

mentioning

confidence: 99%

Mussel‐Inspired Flexible, Wearable, and Self‐Adhesive Conductive Hydrogels for Strain Sensors

Bei

Huang

et al. 2019

Macromol. Rapid Commun.

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delamination of electronic conductors and substrates pose significant challenges in strain sensor applications such as detection of biological signals of human motion. [7] Furthermore, these traditional sensors are mounted on the skin by additional adhesives, mechanical clamps, or straps to achieve long-term practical application. [8] Currently, researchers have focused on identifying new promising candidate materials to overcome these defects.Hydrogels are three-dimensional (3D) polymeric networks with good stretchability, viscoelasticity, and swelling properties. [9] Due to their outstanding performance, many stretchable hydrogels have been increasingly applied to the field of wearable strain sensors. [10][11][12][13][14] For instance, Li et al. [15] developed a dual physically crosslinked polymer hydrogel with hydrogen bonding and ionic coordination. As a strain sensor, it has high sensitivity to pressure and deformation and can detect the human body movement. However, this hydrogel requires additional double-sided tape to be attached to the skin due to the lack of self-adhesion, which limits its application in wearable devices. Thus, an extended function (e.g., self-adhesive performance) is promising for motion detection and allows easy skin adhesion. Currently, the development of a hydrogel-based composite strain sensor with excellent stretchability and selfadhesive properties remains a considerable challenge. Recently, mussel-inspired adhesive hydrogels have demonstrated excellent performance and served as an inspiration for the design and fabrication of other types of self-adhesive hydrogels. Mussels can firmly adhere to all surfaces by noncovalent and covalent chemical interactions regardless of surface roughness. [16] Dopamine (DA), which has a protein-catechol group that is similar to that used in mussel adhesion, has been widely used to fabricate selfadhesive and conductive hydrogels. [17] More importantly, DA provides a new perspective for the development of wearable strain sensors with excellent self-adhesive properties. For instance, Liu et al. [18] reported a hydrogel-based self-adhesive and self-healing epidermal strain sensor by adding Polydopamine (PDA) to PVA; the developed sensor can detect minute epidermal deformations (0.1% strain) and large body movements (10-75% strain) such as throat vibration and finger bending. In addition, it can be used in the field of low-intensity strain sensing. Furthermore, Zhang et al. [19] prepared a conductive, healable, and self-adhesive hydrogel-based sensor by dynamic supramolecular cross-linkingThe latest generation of wearable devices features materials that are flexible, conductive, and stretchable, thus meeting the requirements of stability and reliability. However, the metal conductors that are currently used in various equipments cannot achieve these high performance expectations. Hence, a mussel-inspired conductive hydrogel (HAC-B-PAM) is prepared with a facile approach by employing polyacrylamide (PAM), dopamine-functionalized hyaluronic acid (HAC), ...

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mentioning

confidence: 99%

Mussel‐Inspired Flexible, Wearable, and Self‐Adhesive Conductive Hydrogels for Strain Sensors

Bei

Huang

et al. 2019

Macromol. Rapid Commun.

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“…Highly stretchable resistive type strain sensors have been developed using mechanisms such as crack propagation in thin films or the disconnection/tunnelling effect between conductive fillers [362,363]. Materials such as liquid metals [59,60,[370][371][372], metal nanowires/nanostructures [315,[373][374][375], carbon black [100,101], CNT [90,[377][378][379][380][381], graphene [94,[382][383][384], ionic liquids [385][386][387][388] and hydrogels [116,329,[389][390][391] have been used to fabricate resistive strain sensors.…”

Section: Resistive Strain Sensorsmentioning

confidence: 99%

“…Hydrogel strain sensors made of ionic conductors gained a huge interest in the recent past due to their excellent transparency, biocompatibility and self healing properties [116,329,[389][390][391]. A self healing hydrogel-based strain sensor able to withstand strains up to 1000% with a gauge factor of 1.51 is displayed in Figure 8a [116].…”

Section: Resistive Strain Sensorsmentioning

confidence: 99%

Flexible Sensors—From Materials to Applications

et al. 2019

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Flexible sensors have the potential to be seamlessly applied to soft and irregularly shaped surfaces such as the human skin or textile fabrics. This benefits conformability dependant applications including smart tattoos, artificial skins and soft robotics. Consequently, materials and structures for innovative flexible sensors, as well as their integration into systems, continue to be in the spotlight of research. This review outlines the current state of flexible sensor technologies and the impact of material developments on this field. Special attention is given to strain, temperature, chemical, light and electropotential sensors, as well as their respective applications.

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“…Thus, a moderate network density induced by the copolymerization of allyl cellulose and acrylic acid contributed to the acquisition of remarkable mechanical performance by the CHs. In addition, low-modulus sensors would more easily detect micro strains of the skin, and the combination of high stretchability and low modulus would make hydrogels well adaptable to the epidermis [23]. Obviously, CH3 had a low tensile modulus (35 KPa) compared to human skin (2-80 KPa of modulus for the dermis, 140-600 KPa of modulus for the epidermis).…”

Section: Mechanical Performancementioning

confidence: 99%

“…In our previous study, ultra-stretchable cellulose ionic hydrogels were prepared by using (NH 4 ) 2 S 2 O 8 to initiate free radical polymerization, then using NaCl to induce physical cross-linking [22]. However, although high mechanical performance was obtained, there remains the challenge of combining the properties of transparency, high sensitivity, and high mechanical performance to construct wearable sensors that imitate the human skin (with 2-80 KPa of modulus for the dermis and 140-600 KPa of modulus for the epidermis) [23][24][25]. Cellulose-based hydrogels in which cellulose is the main scaffold and a synthetic polymer is blended in the system have become a notably attractive option in recent years, because they have many advantages, such as adjustable mechanical properties [19,26,27].…”

Section: Introductionmentioning

confidence: 99%

Highly Stretchable, Strain-Sensitive, and Ionic-Conductive Cellulose-Based Hydrogels for Wearable Sensors

et al. 2019

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To extend the applications of natural polymer-based hydrogels to wearable sensors, it is both important and a great challenge to improve their mechanical and electrical performance. In this work, highly stretchable, strain-sensitive, and ionic-conductive cellulose-based hydrogels (CHs) were prepared by random copolymerization of allyl cellulose and acrylic acid. The acquired hydrogels exhibit high stretchability (~142% of tensile strain) and good transparency (~86% at 550 nm). In addition, the hydrogels not only demonstrate better sensitivity in a wide linear range (0–100%) but also exhibit excellent repeatable and stable signals even after 1000 cycles. Notably, hydrogel-based wearable sensors were successfully constructed to detect human movements. Their reliability, sensitivity, and wide-range properties endow the CHs with great potential for application in various wearable sensors.

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A compliant, self-adhesive and self-healing wearable hydrogel as epidermal strain sensor

Abstract: A compliant, self-adhesive and self-healing epidermal strain sensor that shows excellent sensing performance at ultra-low and high strain.

Cited by 174 publications

References 42 publications

Mussel‐Inspired Flexible, Wearable, and Self‐Adhesive Conductive Hydrogels for Strain Sensors

Mussel‐Inspired Flexible, Wearable, and Self‐Adhesive Conductive Hydrogels for Strain Sensors

Flexible Sensors—From Materials to Applications

Highly Stretchable, Strain-Sensitive, and Ionic-Conductive Cellulose-Based Hydrogels for Wearable Sensors

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