A sweat-pH-enabled strongly adhesive hydrogel for self-powered e-skin applications

Zhang, Lei; Wang, Siheng; Wang, Zhuomin; Huang, Zhen; Sun, Peng; Dong, Faqin; Li, He; Wang, Dan; Xu, Xu

doi:10.1039/d3mh00174a

Cited by 33 publications

(7 citation statements)

References 64 publications

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“…Flexible wearable strain sensors have attracted wide attention due to their unique characteristics such as good electrical conductivity, high flexibility and ductility, , strain sensitivity, and environmental adaptability. They can meet the growing demands of wearable electronic devices, , biomedical monitoring, human–computer interaction, electronic skin, , tissue engineering technologies, and other aspects. As a widely used raw material for soft electronic products, conductive hydrogels can imitate human skin to perceive various stimulus signals (stress, , strain, , and temperature) and convert them into electrical signals, such as resistance or capacitance, for signal monitoring of human activity.…”

Section: Introductionmentioning

confidence: 99%

Mussel-Inspired Wet-Adhesive Multifunctional Organohydrogel with Extreme Environmental Tolerance for Wearable Strain Sensor

Shang,

Liu,

Sun

et al. 2023

ACS Appl. Mater. Interfaces

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As a flexible artificial material, the conductive hydrogel has broad application prospects in flexible wearable electronics, soft robotics, and biomedical monitoring. However, traditional hydrogels still face many challenges, such as long-term stability, availability in extreme environments, and long-lasting adhesion to the skin surface under sweaty or humid conditions. To circumvent the above issues, one kind of ionic conductive hydrogel was prepared by a simple one-pot method that dissolved chitosan (CS), 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), tannic acid (TA), and 2-methoxy-ethyl acrylate (MEA) into dimethyl sulfoxide (DMSO)/H2O solvent. The resulting hydrogel showed excellent tensile properties (1440%), extreme environmental tolerance (−40–60 °C), adhesion (72 KPa at porcine skin), ionic conductivity (0.87 S m–1), and high-efficiency antibacterial property. Furthermore, the produced organohydrogel strain sensor exhibited high strain sensitivity (GF = 4.07), excellent signal sensing capabilities (human joint movement, microexpression, and sound signals), and long-term cyclic stability (400 cycles). Looking beyond, this work provides a simple and promising strategy for using hydrogel sensors in extreme environments for e-skin, health monitoring, and wearable electronic devices.

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Section: Introductionmentioning

confidence: 99%

Mussel-Inspired Wet-Adhesive Multifunctional Organohydrogel with Extreme Environmental Tolerance for Wearable Strain Sensor

Shang,

Liu,

Sun

et al. 2023

ACS Appl. Mater. Interfaces

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“…However, the interfacial adhesion is relatively weak to low surface energy adherends such as PE, PC, and PMMA because van der Waals and hydrophobic associations prevail at the interfaces. The interfacial toughness of mTA 5 -PAA/PEI 3 exceeds that of many reported wTA PEC hydrogel materials, such as polyTA–PETEA–PEGDA–agar and PAGU hydrogels with wet interfacial toughness values of 858 and 818 J/m 2 , respectively, and the interface toughness of our work is approximately 1.8 times that of both (Figure I and Table S3) ,,– and higher than that of common commercial TAs, such as commercially available cyanoacrylate (Histoyl) and fibrin sealant (Tisseel), both of which have interfacial toughness less than 20 J/m 2 …”

Section: Resultsmentioning

confidence: 45%

“…The toughness of the mTA 3 -PAA/PEI 3 hydrogel is 1.7 times and 1.8 times that of the two hydrogels (Figure H and Table S2). – …”

Section: Resultsmentioning

confidence: 99%

Robust but On-Demand Detachable Wet Tissue Adhesive Hydrogel Enhanced with Modified Tannic Acid

Wang,

Huang,

et al. 2023

ACS Appl. Mater. Interfaces

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Adhesives with robust but readily detachable wet tissue adhesion are of great significance for wound closure. Polyelectrolyte complex adhesive (PECA) is an important wet tissue adhesive. However, its relatively weak cohesive and adhesive strength cannot satisfy clinical applications. Herein, modified tannic acid (mTA) with a catechol group, a long alkyl hydrophobic chain, and a phenyl group was prepared first, and then, it was mixed with acrylic acid (AA) and polyethylenimine (PEI), followed by UV photopolymerization to make a wet tissue adhesive hydrogel with tough cohesion and adhesion strength. The hydrogel has a strong wet tissue interfacial toughness of ∼1552 J/m2, good mechanical properties (∼7220 kPa cohesive strength, ∼873% strain, and ∼33,370 kJ/m3 toughness), and a bursting pressure of ∼1575 mmHg on wet porcine skin. The hydrogel can realize quick and effective adhesion to various wet biological tissues including porcine skin, liver, kidney, and heart and can be changed easily with triggering urea solution to avoid tissue damage or uncomfortable pain to the patient. This biosafe adhesive hydrogel is very promising for wound closure and may provide new ideas for the design of robust wet tissue adhesives.

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“…To further verify the dynamically reversible phase separation behavior of the polymer chains in aqueous solutions, we performed in situ Raman spectroscopy on the CNF/P(AA- co -AAm) hydrogel in a closed cooling and heating cycle to observe the polymer composition interactions (Figure d). The two-dimensional (2D) Raman images demonstrate a dynamic transition of the total integrated area of the peaks at 1430 cm –1 (−NH 2 from PAAm) and 1698 cm –1 (−COOH from PAA or CNF) with cooling and heating processes. , The fluorescence intensity can be used to directly reflect the H-bonding interactions of the system. The loose H-bond cross-links (the red–yellow regions) are observed in the initial state (35 °C), which transform into denser H-bond cross-links (the blue–green regions) after cooling for 10 min; however, as expected, on heating for 10 min, the system shows decayed H-bond cross-links (the red–yellow regions).…”

Section: Resultsmentioning

confidence: 99%

“…The two-dimensional (2D) Raman images demonstrate a dynamic transition of the total integrated area of the peaks at 1430 cm −1 (−NH 2 from PAAm) and 1698 cm −1 (−COOH from PAA or CNF) with cooling and heating processes. 27,28 The fluorescence intensity can be used to directly reflect the H-bonding interactions of the system. The loose H-bond cross-links (the red−yellow regions) are observed in the initial state (35 °C), which transform into denser H-bond cross-links (the blue−green regions) after cooling for 10 min; however, as expected, on heating for 10 min, the system shows decayed Hbond cross-links (the red−yellow regions).…”

Section: Resultsmentioning

confidence: 99%

Temperature-Mediated Phase Separation Enables Strong yet Reversible Mechanical and Adhesive Hydrogels

Zhang

Wang

et al. 2023

ACS Nano

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Hydrogels with strong yet reversible mechanical and adhesive properties fabricated in a facile and friendly manner are important for engineering and intelligent electronics applications but are challenging to create and control. Existing approaches for preparing hydrogels involve complicated pretreatments and produce hydrogels that suffer from limited skin applicability. Copolymerized hydrogels are expected to present an intriguing target in this field by means of thermoresponsive features, while the perceived intrinsic flaws of brittleness, easy fracture, and weak adhesion enervate the development prospects. Herein, we report a hydrogel with strong yet reversible mechanical and adhesive properties using cellulose nanofibrils to simultaneously address multiple dilemmas inspired by a temperature-mediated phase separation strategy. This strategy applies temperature-driven formation and dissociation of hydrogen bonds between common copolymers and cellulose nanofibrils to trigger the onset and termination of phase separation for dynamically reversible on-demand properties. The resulting hydrogel exhibits up to 96.0% (117.2 J/m2 vs 4.8 J/m2 for interfacial toughness) and 85.7% (0.02 MPa vs 0.14 MPa for mechanical stiffness) adhesive and mechanical tunability when worked on skin, respectively. Our strategy offers a promising, simple, and efficient way to directly achieve robust adhesion performance in one step using common copolymers and biomass resources, with implications that could go beyond strong yet adhesive hydrogels.

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A sweat-pH-enabled strongly adhesive hydrogel for self-powered e-skin applications

Abstract: On-skin hydrogel electrodes are poorly conformable in sweaty scenarios due to low electrode–skin adhesion resulting from the sweat film formed on the skin surface, which seriously hinders practical applications. In...

Cited by 33 publications

References 64 publications

Mussel-Inspired Wet-Adhesive Multifunctional Organohydrogel with Extreme Environmental Tolerance for Wearable Strain Sensor

Mussel-Inspired Wet-Adhesive Multifunctional Organohydrogel with Extreme Environmental Tolerance for Wearable Strain Sensor

Robust but On-Demand Detachable Wet Tissue Adhesive Hydrogel Enhanced with Modified Tannic Acid

Temperature-Mediated Phase Separation Enables Strong yet Reversible Mechanical and Adhesive Hydrogels

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