Mussel-inspired nanocomposite hydrogel-based electrodes with

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Mussel-inspired nanocomposite hydrogel-based electrodes with reusable and injectable properties for human electrophysiological signals detection Xiaofeng pan, Qinhua Wang, Peng He, Kai Liu, Yonghao Ni, Xinhua Ouyang, Lihui Chen, Liulian Huang, Hongping Wang, and Yue Tan ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.9b00579 • Publication Date (Web): 22 Mar 2019 Downloaded from http://pubs.acs.org on March 22, 2019

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ACS Sustainable Chemistry & Engineering

Mussel-inspired nanocomposite hydrogel-based electrodes with reusable and injectable properties for human electrophysiological signals detection

Xiaofeng Pan #a, Qinhua Wang#a, Peng Hea , Kai Liua,*, Yonghao Nia,b, Xinhua Ouyanga, Lihui Chena, Liulian Huanga, Hongping Wangc , Yue Tana

a College

of Material Engineering, Fujian Agriculture and Forestry University, No. 15

Shangxiadian Road, Cangshan District, Fuzhou City, Fujian Province 350002, China b Limerick

Pulp and Paper Centre, Department of Chemical Engineering, University of

New Brunswick, Fredericton, New Brunswick E3B5A3, Canada c

Jinshan College, Fujian Agriculture and Forestry University, No. 15 Shangxiadian Road, Cangshan District, Fuzhou City, Fujian Province 350002, China

#: These authors contributed equally to this work. Corresponding author: Kai Liu Fujian Agriculture and Forestry University, Fuzhou 350002, China E-mail: [email protected]

1

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Abstract Recently, ion-conducting hydrogels have received much attention in the preparation of non-invasive electronics. However, there have been few studies on the simultaneous integration of multi-properties of hydrogels to meet the actual needs of flexible electrodes. Herein, we prepared mussel-inspired proanthocyanins (PC)-coated cellulose nanofibrils (CNF) nanocomposites, which were dispersed in the guar gum (GG) and glycerol solution to prepare a PC-CNF-GG-glycerol hydrogel. This hydrogel exhibits great adhesion (7.9 KPa) and UV-blocking ability (82 %). Moreover, the borax solution using as a crosslinker also imparts ion-conducting property to the hydrogel, and the strain sensor fabricated by the hydrogel exhibits low-weight detection ability (200 mg) and fast response speed (33 ms). The adhesive, conductive, and injectable PC-CNFGG-glycerol hydrogel can also be used for preparing wearable, portable and editable electrodes. The new electrode can accurately detect electrophysiological (EP) signals of human. Interestingly, the hydrogel electrode also has advantages of reusability. In summary, this ion-conducting hydrogel has the potential to become a new generation of portable and biofriendly bioelectrodes, sensor, and dressings. Keywords: mussel-inspired, cellulose nanofibrils, conductive hydrogel, injectable electrode, reusable

Introduction 2


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Hydrogels are elastic soft materials including a three-dimensional polymer network. 1-3

In recent years, they have been widely studied and applied in the fields of tissue

repair, 4,5 drug delivery, 6,7 cell culture, 8,9 skin dressings,6, 10 sewage treatment, 10-12 etc. Especially, conductive hydrogels (CHs) with excellent conductivity and elasticity have great application prospects in wearable electronics, 15,16

13,14

triboelectric nanogenerators,

electrodes for human health monitoring. 17 Currently, the most widespread approach to develop CHs is to incorporate

conductive polymers, carbon materials or metal-based nanowires into the hydrogel system.18-21 However, most conductive materials are high-cost. In addition, the conductive materials are easy to aggregate in hydrogel,

22,23which

greatly affects the

conductivity of the hydrogel. More importantly, the damage of most conductive materials to human tissues is still unknown. For instance, many studies have shown that carbon nanotubes have high toxicity.24-26 Another universal route to prepare CHs is to use a soluble salt solution as a hydrogel dispersion medium.27,28 The ions generated by the ionization of the salt solution is able to form a penetrating ion conductive pathway between the polymer networks in the hydrogel.29 The ion hydrogels are soft, stretchable, inexpensive, and electrically conductive.30 Therefore, Zhao et al.31 presented that ion hydrogels were the adaptable carriers as non-invasive electronic devices for humanmachine interfaces. As an ion hydrogel-based non-invasive electronics, especially soft electrodes for human electrophysiological (EP) signal collection, the great adhesion of the hydrogel may promote better contact between the device and the human skin surface, therefore 3



outputting more stable data.32 However, most hydrogels lack enough self-adhesive property. Moreover, hydrogels are difficult to reshape macro-structures to match irregular substrates such as human skin, which also reduce the accuracy of the sensing.33The preparation of the injectable and adhesive CHs is a useful solution to address this problem, which can be adhered tightly to the irregular surface of the skin without penetration.22 More importantly, the traditional disposable electrode cannot be reused, so an injectable hydrogel with rapid self-healing capability can greatly increase the service life and significantly reduce the cost of the electrodes.34 Similarly, the environmental problems caused by the disposable electrodes need to be solved.35At present, there are many studies on conductive hydrogels with single self-adhesive, injectable, self-healing, or degradable property, but it is still a huge challenge to prepare hydrogel with integrated all of the above properties. Guar gum (GG) polymer is a natural polysaccharide with excellent biocompatibility and degradability,36 which is a suitable material for the preparation of the skin affinity hydrogel.37 In our previous work,38 we prepared an ionic conductive GG-glycerol hydrogel by incorporating a small amount of glycerol into the GG-borax system. The dynamic interaction between water-glycerol-borax imparts injectable, ultra-fast selfhealing, and stretchable properties to the hydrogel. Herein, inspired by mussel adhesion chemistry, cellulose nanofibrils (CNF) was used as a template for proanthocyanins (PC) coating to obtain PC-CNF nanocomposites. Next, the PC-CNF nanocomposites are oxidized and incorporated into the GG-glycerol hydrogel system to obtain the PC-CNF-GG-glycerol hydrogel. The new hydrogel 4


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inherits the great injectability, conductivity, stretchable and self-healing properties of the GG-glycerol hydrogel. At the same time, PC has a rich phenolic hydroxyl group, which not only gives the new hydrogel excellent adhesion property, but also imparts the hydrogel with an efficient UV-shielding ability. Therefore, the PC-CNF-GGglycerol hydrogel can be used as UV-shielding and moisturizing wearable dressings. Interestingly, the conductive PC-CNF-GG-glycerol hydrogel is also can be employed as an injectable and portable non-invasive electrode for the detection of human electrophysiological (EP) signals. In addition, the excellent self-healing ability of the PC-CNF-GG-glycerol hydrogel allows the hydrogel electrodes to maintain a high reusable rate. Most importantly, the PC-CNF-GG-glycerol hydrogel synthesized with natural materials are biofriendly. In brief, we believe that the multi-functional PC-CNFGG-glycerol hydrogel is more attractive for the preparation of new generation noninvasive electrodes, strain sensors, and dressings.

Experimental section Materials Cellulose nanofibrils (CNF, 0.83 wt%) oxidized by TEMPO-mediated oxidation was from Haojia Cellulose Co., Ltd (Tianjin China). Proanthocyanins (PC) was from Rhawn Technology Development Co. Ltd. (Shanghai, China). Ferric chloride hexahydrate (FeCl3.6H2O), tris(hydroxymethyl) aminomethane (Tris), glycerol, and borax (Na2B4O7·10H2O, Mw = 381.37 g/mol) were from Aladdin reagent Co., Ltd (Shanghai, China). Guar gum (99.99% purity) was from Chengdu Aike Reagent Co., Ltd (Chengdu, China). 5



Preparation of the PC-CNF nanocomposites First, 6.025 ml CNF suspension (0.83 wt%) was diluted with deionized water to obtain the 10 ml CNF suspension (0.5 wt%). Tris buffer solution (1 M) was introduced into the CNF suspension (0.5 wt%) until pH was adjusted to 8. Subsequently, 0.02 g PC was added and the mixed suspension was stirred for 8 h at room temperature. Finally, the PC-CNF nanocomposites were obtained. Preparation of the PC-CNF-GG-glycerol hydrogel First, FeCl3 ·6H2O power, 8 ml deionized water, and 2 ml glycerol were added to the above PC-CNF nanocomposites. After reaction for 15 min, 0.3 g GG was added and completely dissolved in the above mixture, and then 4ml borax solution of 5 wt% was added to obtain the PC-CNF-GG-glycerol hydrogel. Similarly, 8ml borax solution was also added to the mixture. However, no hydrogel can be formed (Figure S1). As a comparison, 0.3 g GG and 2 ml glycerol were completely dissolved in the 18ml deionized water, and then 4 ml borax solution of 5 wt% was added to obtain the GGglycerol hydrogel. Then, 0.3 g GG was completely dissolved in the 20ml deionized water, and 5 wt% borax solution was added to obtain the GG hydrogel. Field-emission scanning electron microscopy (FE-SEM) analysis The CNF and PC-CNF samples were prepared by dropping the CNF and PC-CNF dispersion onto the single crystal silicon wafer, and then placed in a room overnight until the samples were completely dried. The dried sample was coated with gold for further analysis. For the cross-section observation, the GG-glycerol and PC-CNF-GG-glycerol 6


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hydrogels were freeze-dried for 48 h, and the residual glycerol was washed out and then freeze-dried for another 48 h. The hydrogel samples were cryofractured in liquid nitrogen and then coated with conductive gold before the test. The morphology of the CNF, PC-CNF nanocomposites, GG-glycerol, and PC-CNF-GG-glycerol hydrogels were observed by a field-emission scanning electron microscopy. (FE-SEM, Nova Nano SEM 230, FEI. SRO, Czech Republic). XPS spectra of C1s for the PC, CNF, and PC-CNF nanocomposites The chemical compositions of the PC, CNF, and PC-CNF nanocomposites were measured using an X-ray photoelectron spectrometer (XPS, Thermo Scientific ESCALAB 250Xi). The neutral C 1s peak (C-C (H), 284.6 eV) was applied as a reference for charge correction. Anti-UV and adhesion studies of the PC-CNF-GG-glycerol hydrogel A thin hydrogel layer (1 mm) was coated on the transparent PET film (UV transmittance: 93%), and the UV-shielding (365 nm) efficiency of the hydrogel was measured using an optical transmittance meter (LS108H Shenzhen Linshang Technology Co., Ltd.). The hydrogel adhesion strength was tested using the previous methods.39 In detail, the test materials (fresh hog skin, thin wood, and copy paper,1cm width × 1cm length) were adhered on the bottom surface of the thin copper plate (1cm width × 8cm length) respectively, and then the hydrogel was sandwiched between the test materials. Next, the sample was subjected to a lap shear test at a speed of 10 mm/min on a digital tensile machine (KJ-1065B, Kejian instrument Co. Ltd, Dongguan, China). 7



Adhesion strength =

𝐹𝑚𝑎𝑥 𝑆

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(1)

Where Fmax was the maximum load, S was the bonded area (1 cm2). Conductivity measurement of the PC-CNF-GG-glycerol hydrogel The

conductivity

of

the

PC-CNF-GG-glycerol

hydrogel

film

(20 mm

length × 20 mm width × 1 mm thickness) was tested using a four-point probe strategy.40 Self-healing study of the PC-CNF-GG-glycerol hydrogel According to the previous studies,29 the self-healing efficiency of the PC-CNF-GGglycerol hydrogel was quantitatively evaluated by the recovery of storage modulus (G') with performing strain sweeps from 1% to 1000% and back to 1% at a frequency of 1 Hz. Self ― healed efficiency = η = G′𝐴/ G′𝐵

(2)

Where GB' was the storage modulus of 1% strain (1% to 1000% process), GA' was the storage modulus of 1% strain (1000% to 1% process). Human electrophysiological (EP) signals detection with the PC-CNF-GG-glycerol hydrogel-based electrode First, the test site (left forearm, right forearm, and right ankle) of a volunteer (a 22year-old healthy man) was scrubbed with absolute ethanol and air dried. Then the test site was connected with the multi-channel physiological signal acquisition and process system (RM6240CD, Chengdu Instrument Factory, China) using a wire. Secondly, the PC-CNF-GG-glycerol hydrogel was injected through a syringe at the above test site, and the electrocardiograph (ECG) signal of the volunteer was displayed by a computer. Similarly, the hydrogel was injected on the muscle surface of the right 8


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forearm to measure the surface electromyography (sEMG) signal of the volunteer under different muscle states.41 In order to assess the signal processing capability of the injectable hydrogel, we further analyzed the signal-to-noise ratio (SNR) of the hydrogel, and selected the commercial Ag/AgCl electrode as a comparison, the SNR is defined as: 𝑆𝑁𝑅𝑑𝐵 = 10log10

𝑉𝑠𝑖𝑔𝑛𝑎𝑙 2

( ) 𝑉𝑛𝑜𝑖𝑠𝑒

( )

= 20log10

𝑉𝑠𝑖𝑔𝑛𝑎𝑙 𝑉𝑛𝑜𝑖𝑠𝑒

(3)

where Vnoise was estimated from the sEMG signals gathered in the settling trials and Vsignal was estimated from the muscle tension data in the test (the signal selected in this test comes from the sEMG signal of the forearm skin when the volunteer makes a fist). V was the root mean square (RMS) of the data.42

Results and discussion Design route of the PC-CNF-GG-glycerol hydrogel Most hydrogels do not have sufficient adhesion, resulting in a lack of affinity with skin and tissue of human. In order to synthesize an adhesive hydrogel, mussel-inspired polydopamine (PDA) composite hydrogels have been extensively prepared by a lot of researchers due to the strong adhesion and great biocompatibility of the PDA.43,44 In addition to the PDA, Messersmith et al.45 proposed that plant polyphenols also have a similar adhesive effect compared to PDA. Therefore, Xu et al. synthesized tannic acid (TA)-coated cellulose nanocrystals (CNCs) composites and incorporated them into polyacrylic acid (PAA) and poly(vinyl alcohol) (PVA) to prepare adhesive hydrogel.46,47 However, TA has a carcinogenic effect on the human body, and it has 9



visible harm to the water environment.48 Herein, PC, which is non-toxic, biocompatible, and antioxidant,49 was used as an alternative for the preparation of adhesive hydrogel. Figure 1 presents the detailed design route of the PC-CNF-GG-glycerol hydrogel. First, we prepared the PC-CNF nanocomposites using CNF as a template due to the high specific surface area of CNF.50-52Next, Fe3+ ions are added to the PC-CNF nanocomposites to oxidize the PC layer. As depicted in Figure S2, the oxidized PCCNF nanocomposites become brown from dark red. Finally, the oxidized PC-CNF nanocomposites were uniformly dispersed in the GG-glycerol-water solution, and the borax was used as a crosslinking agent to prepare a self-adhesive PC-CNF-GG-glycerol hydrogel. Figure 2a presents the FE-SEM images of the CNF and PC-CNF nanocomposites, a large number of massive protrusions appear on the surface of the PC-CNF compared to the flat CNF surface, which should be the PC coated on the CNF surface. Moreover, according to the chemical structure of CNF and PC (Figure 2b) and the XPS highresolution C1s curve (Figure 2c, Table S1), the PC-CNF nanocomposites have a lower ratio of C=O (288.5V) group compared to the pure CNF, indicating that a part of the free -COOH groups of the CNF, which are derived from the TEMPO oxidation for the cellulose,53 are involved in the reaction with the PC or covered by the PC. More importantly, the PC-CNF dispersion exhibited a red color compared to the white CNF dispersion. Over all, these results together verify that the PC is well coated on the CNF surface.

10


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Figure 1. Design strategy of the PC-CNF-GG-glycerol hydrogel.

Figure 2. Analysis of the PC and PC-coated CNF. (a) FE-SEM images of (i) the CNF; (ii) the PC-CNF. (b) Chemical compositions of the CNF and PC. (c) XPS spectra of C 1s for the dried CNF, PC, and PC-CNF nanocomposites. Adhesion and UV-shielding ability of the PC-CNF-GG-glycerol hydrogel According to the cross-section morphology of the hydrogel in Figure 3a, a lot of smooth inner walls and large pores can be observed in the GG-glycerol hydrogel. In contrast, the PC-CNF-GG-glycerol hydrogel exhibits a lot of small pores, in which are filled a large number of interwoven short fibers. This result indicates that the PC-CNF 11



nanocomposites are uniformly dispersed in the PC-CNF-GG-glycerol hydrogel. Given the rich phenolic hydroxyl groups on the PC surface, the hydrogel containing PC-CNF nanocomposites exhibits repeatable adhesion to different substrates such as wood, paper, and hog skin (Figure 3b). Here, the adhesive strength of the hydrogel was affected by the adhesion of the phenolic hydroxyl group and the substrate, as well as the surface morphology of substrate. The surface of the wood is porous and rough, and the prepared hydrogel has great fluidity, and it easily penetrates into the voids of the wood, thus greatly increasing the adhesive area. In addition, the wood is mainly composed of cellulose, and the surface of the wood has a large amount of hydroxyl groups, which also promotes hydrogen bonding between the hydrogel and the wood. On the contrary, the surface of the pig skin has smooth grease, which greatly affected the adhesive effect. Similarly, the surface of the copy paper contains a large amount of inorganic CaCO3 particles (> 50%, fillers), and the polished paper is very smooth, which is not conducive to the adhesion of the hydrogel. In summary, this adhesion effect is close to the previously reported mussel-inspired TA hydrogel.47 Moreover, medical institutions at high altitude areas are highly susceptible to UV radiation.41 There is an urgent need for a convenient and wearable material. Interestingly, the PC-CNF-GG-glycerol hydrogel demonstrates excellent UV-shielding ability. Since there is a large amount of phenolic hydroxyl groups on the PC, this can function as a UV absorber.54 In the UV-shielding test, the thin film (1 mm) of the PCCNF-GG-glycerol hydrogel can block up to 82% of UV light (365nm) (Figure 3c), this UV shielding efficiency is much higher than that of the GG-glycerol hydrogel. 12


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Meanwhile, the glycerol in the PC-CNF-GG-glycerol hydrogel can moisturize the skin. We believe that the UV-shielding PC-CNF-GG-glycerol hydrogel has the potential to develop a non-permeable, moisturizing, and wearable dressing.

Figure 3. (a) FE-SEM images of the cross-section morphology of (i) the GG-glycerol hydrogel; (ii) the PC-CNF-GG-glycerol hydrogel. (b) Repeatable adhesion property of the PC-CNF-GG-glycerol hydrogel to various substrates by cyclic adhesion tests. (c) UV-shielding rates of the GG-glycerol and PC-CNF-GG-glycerol hydrogel films. Injectable, stretchable, and conductive properties of the PC-CNF-GG-glycerol hydrogel Recently, we presented that the injectability of the GG-glycerol hydrogel was attributed to the fact that the addition of glycerol hindered the attachment of borax and GG polymer, making the hydrogel in a fluid-like state.38 Here, the PC-CNF nanocomposites apparently do not break the injectability of the PC-CNF-GG-glycerol hydrogel. The PC-CNF-GG-glycerol hydrogel inherits the injectable properties of the GG-glycerol hydrogel. Therefore, the PC-CNF-GG-glycerol hydrogel can be injected to a shape of the "FAFU" (Figure 4a). The injectability of the hydrogel is shown to be related to the shear thinning property of the hydrogel.22 The injectable hydrogels are expected to be used in many fascinating areas such as cell scaffolding, tissue culture, 13



wound repair, and 3D printed wearable devices. Moreover, the PC-CNF-GG-glycerol hydrogel demonstrates stretchable ability. In the manual tensile test (Figure 4b), the 2 cm hydrogel strip can be stretched to reach 18 cm. More interestingly, the Na+ ions formed by the borax solution and Fe3+ ions impart high conductivity to the hydrogel (0.023 S/cm). 33,38 The blue light-emitting diode (LED) bulb is easily lighted by the GG-glycerol hydrogel and the PC-CNF-GG-glycerol hydrogel (Figure S3, 4c). Nowadays, CHs pressure sensors have been extensively studied.29 Here, we study the pressure sensitivity of the PC-CNF-GG-glycerol hydrogel, which is a key parameter for the sensor. As presented in Figure S4a, a strain sensor constructed by the PC-CNFGG-glycerol hydrogel and PET film was prepared, and a water droplet of 200 μL was dropped on the strain sensor surface from a height of 20 cm, the resistance changes of the strain sensor were monitored and recorded during the test process. As shown in Figure S4, the hydrogel sensor even can detect a 200 mg water droplet (response time=33 ms). Compared to various hydrogel sensors, the PC-CNF-GG-glycerol hydrogel sensor has abilities of sensitive sensing and fast response ability, which may be attributed to the addition of glycerol to cause the hydrogel to have a softer mechanical property.38 When a small force is applied to the hydrogel such as water droplets, the hydrogel will undergo a large deformation (guar gum polymer network shrinkage), which will then cause a change in the internal ion (Na+ and Fe3+) concentration of the hydrogel sensor, ultimately resulting in change of hydrogel sensor resistance.

55

For instance, the GG hydrogel without glycerol showed insensitivity to 14


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small pressure (Figure S5). Most importantly, to the best of our knowledge, according to previous studies (Table S2 , S3), the 200 mg weight and 33 ms response time are close to the limits that most sensors can achieve, proving that the conductive PC-CNFGG-glycerol hydrogel possesses the ability to prepare an ultrasensitive sensor.30 Here, a self-adhesive, stretchable, and conformable hydrogel sensor has been proven to be useful for the detection of human limb movements (Figure S6). Simply put, the multifunctional PC-CNF-GG-glycerol hydrogel has a broad application space in fields of various wearable sensors.56

Figure 4. (a) Injecting the PC-CNF-GG-glycerol hydrogel to a “FAFU” shape through a syringe. (b) Stretchable and (c) conductive properties of the PC-CNF-GG-glycerol hydrogel. Human electrophysiological (EP) signals detection In addition to the preparation of sunscreen dressings and ultra-sensitive strain sensors, the mussel-inspired injectable and conductive PC-CNF-GG-glycerol hydrogel also can be applied as hydrogel electrodes for human EP signals detection. To explore the feasibility of an injectable hydrogel-based electrode, a test platform as presented in Figure 5a was fabricated. The detailed composition of the platform and the test procedure are shown in the experimental section. It should be pointed out that the hydrogel electrode is injected onto the skin surface after the wire and the testing 15



equipment are connected. This platform is applied to detect human electrocardiograph (ECG) and surface electromyography (sEMG) signals (the test volunteer is a 22-yearold healthy man). 57 The human ECG signal detection approach is exhibited in Figure 5b (the volunteer is in a quiet state). According to the test result (Figure 5c), it can be found that the ECG signal recorded by the injectable hydrogel electrode exhibits a complete ECG waveform (the characteristic P-Q-R-S-T segment). This is close to the original data detected by the commercial electrode (Figure S7). Furthermore, the PC-CNF-GG-glycerol hydrogel was injected onto the skin surface of the forearm muscles (Figure 5d), and then the sEMG signals of the skin under different gesture states were collected (Video S1).58As seen in Figure 5e, the test result shows a remarkable signal responsiveness capability, which can be used to easily distinguish various muscle states. To further analyze the signal data, the signal-to-noise ratio (SNR) of the PC-CNF-GG-glycerol hydrogel electrode was calculated. It can be found from the inset of Figure 5e that the SNR is 12.7 dB when the volunteer makes a fist, which is very close to that of the commercial Ag/AgCl electrode (the SNR of the commercial electrode is 13.1dB, Figure S8). These results reveal that the hydrogel electrode can be used to measure the high-quality EP recordings.42 Interestingly, the strong adhesion of the PC-CNF-GG-glycerol hydrogel based on mussel-inspired chemistry allows it to be better contacted with the nature skin without penetration. Similarly, compared to the commercial Ag/AgCl electrodes, the injectable hydrogel electrode holds lots of advantages, such as controlled release, high portability, 16


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and excellent moisture retention. Most importantly, as far as we know, this is the first example of an injectable hydrogel-based electrode, which provides a feasible new route for preparing a next-generation of flexible wearable electrodes.

Figure 5. Application of the PC-CNF-GG-glycerol hydrogel-based injectable electrode. (a) Schematic of the injectable hydrogel electrode for human EP signals detection, Scale bar: 5 cm. (b) The ECG signal detection approach. (c) The ECG signals of a volunteer. (d) The sEMG signal detection approach. (e) The sEMG signal of a volunteer 17



under different gestures. Self-healable and reusable properties of the PC-CNF-GG-glycerol hydrogel electrode For hydrogel-based electronics, self-healing property is a critical function that can increase the reuse rate and reduce the costs of devices. Fortunately, based on multiple dynamic crosslinking chemistry, the PC-CNF-GG-glycerol hydrogel exhibits a charming self-healing ability. As shown in Figure 6a, the borax can form reversible bonds with the GG, glycerol,38 and PC.59 Moreover, Fe3+ and -COO- of the TEMPOmediated oxidation CNF also can form ionic coordination.55 The above bonds have a significant improvement for the self-healing property of the hydrogel. Therefore, the broken hydrogel quickly self-healed and successfully light the blue LED bulb. According to the strain sweeps of the PC-CNF-GG-glycerol hydrogel (Figure 6b), the self-healing effect of the prepared hydrogel is great (instant, η= 87.45 %) compared to recent self-healing hydrogels based on different self-healing mechanisms (Table S4). Therefore, the PC-CNF-GG-glycerol hydrogel-based electrode has rapid self-healable and reusable properties.60 In order to investigate the reusable property of the hydrogel electrode, a simple test was designed in Figure S9. The separate hydrogel electrodes injected by a syringe can be self-healed into a complete one immediately, and the self-healed hydrogel can be reloaded in a syringe. Notably, this operation even can be repeated multiple times. Due to the repeatable adhesion and anti-drying (glycerol moisturizing) properties of the hydrogel, the hydrogel electrode even can precisely detect the sEMG signals of human 18


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after 5 times cutting and self-healing processes (Figure S10). In short, the reusable and flexible PC-CNF-GG-glycerol hydrogel electrode greatly reduces electrode waste, which is an important breakthrough compared to disposable electrodes.

Figure 6. (a) The self-healing mechanism of the PC-CNF-GG-glycerol hydrogel. (b) The reciprocating strain sweeps of the PC-CNF-GG-glycerol hydrogel.

Conclusion In summary, we successfully fabricated a mussel-inspired PC-CNF-GG-glycerol hydrogel. The hydrogel demonstrates a high adhesion and UV shielding capacity due to the loading of PC in the hydrogel network. In addition, the hydrogel also holds ionic conductivity, injectability and strain sensitivity. Interestingly, this injectable electrode assembled by the hydrogel integrates editable, and reusable properties, which can be used to precisely detect human ECG and sEMG signals. We believe that this hydrogel made from natural materials offer a new route in preparing UV-shielding dressings, sensors and a new generation of biofriendly electrodes.

Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI: No formed gel after adding 8 ml borax solution of 5 wt% to PC-CNF/GG/Glycerol 19



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mixture; Color of the PC-CNF/Fe3+ nanocomposites; Statistical results of gauss-fitted peak of CNF, PC, and CNF-PC particles; Conductive GG-glycerol hydrogel; Detection of 200μl water droplets; Insensitive GG hydrogel sensor; Minimum pressure detected by various sensors; Response time of recent hydrogel sensors; Detection of human limb movements; The ECG and sEMG signals detected by the commercial electrode; Selfhealing effects of recent gels; Reusable test of the hydrogel electrode; The sEMG signal detected by the re-loaded injectable electrode. (PDF) The injectable PC-CNF-GG-glycerol hydrogel electrode for human sEMG signal detection. (AVI)

Acknowledgments The authors are grateful to the national key research and development program of China (2017YFB0307900) and scientific and technological innovation funding of Fujian

Agriculture

and

Forestry

University

(KFA17551A,

CXZX2017040, KF2015002).

Notes The authors declare no competing financial interest.

References 20


KFA17552A,

Page 21 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(1) Yuk, H.; Zhang, T.; Lin, S.; Parada, G. A.; Zhao, X. Tough bonding of hydrogels to diverse non-porous surfaces. Nat. Mater. 2016, 15 (2), 190-196, DOI 10.1038/nmat4463. (2) Kamoun, E. A.; Kenawy, E.-R. S.; Chen, X. A review on polymeric hydrogel membranes for wound dressing applications: PVA-based hydrogel dressings. J. Adv. Res. 2017, 8 (3), 217233, DOI 10.1016/j.jare.2017.01.005. (3) Zhang, Y. S.; Khademhosseini, A. Advances in engineering hydrogels. Science 2017, 356 (6337), eaaf3627, DOI 10.1126/science.aaf3627. (4) Zhai, X.; Ma, Y.; Hou, C.; Gao, F.; Zhang, Y.; Ruan, C.; Pan, H.; Lu, W. W.; Liu, W. 3DPrinted High Strength Bioactive Supramolecular Polymer/Clay Nanocomposite Hydrogel Scaffold for Bone Regeneration. ACS Biomater. Sci. Eng. 2017, 3 (6), 1109-1118, DOI

10.1021/acsbiomaterials.7b00224. (5) Kamata, H.; Akagi, Y.; Kayasuga-Kariya, Y.; Chung, U.-i.; Sakai, T. "Nonswellable" Hydrogel Without

Mechanical

Hysteresis.

Science

2014,

343

(6173),

873-875,

DOI

10.1126/science.1247811. (6) Ajovalasit, A.; Sabatino, M. A.; Todaro, S.; Alessi, S.; Giacomazza, D.; Picone, P.; Di Carlo, M.; Dispenza, C. Xyloglucan-based hydrogel films for wound dressing: Structure-property relationships. Carbohydr. Polym. 2018, 179, 262-272, DOI 10.1016/j.carbpol.2017.09.092. (7) Wei, W.; Li, J.; Qi, X.; Zhong, Y.; Zuo, G.; Pan, X.; Su, T.; Zhang, J.; Dong, W. Synthesis and characterization of a multi-sensitive polysaccharide hydrogel for drug delivery. Carbohydr.

Polym. 2017, 177, 275-283, DOI 10.1016/j.carbpol.2017.08.133. (8) Dou, X.-Q.; Feng, C.-L. Amino Acids and Peptide-Based Supramolecular Hydrogels for Three-Dimensional

Cell

Culture.

Adv.

Mater.2017, 21


29

(16),

1604062,

DOI


Page 22 of 31

10.1002/adma.201604062. (9) Caliari, S. R.; Burdick, J. A. A practical guide to hydrogels for cell culture. Nat. Methods 2016, 13 (5), 405-414, DOI 10.1038/nmeth.3839 . (10) Wang, M.; Li, X.; Hua, W.; Deng, L.; Li, P.; Zhang, T.; Wang, X. Superelastic threedimensional nanofiber-reconfigured spongy hydrogels with superior adsorption of lanthanide ions and photoluminescence. Chem. Eng. J. 2018, 348, 95-108, DOI 10.1016/j.cej.2018.04.135. (11) Zheng, Y.; Zhu, Y.; Wang, A. Highly efficient and selective adsorption of malachite green onto

granular

composite

hydrogel.

Chem.

Eng.

J.

257,

2014,

66-73,

DOI

10.1016/j.cej.2014.07.032. (12) Dai, L.; Zhang, L.; Wang, B.; Yang, B.; Khan, I.; Khan, A.; Ni, Y. Multifunctional selfassembling hydrogel from guar gum. Chem. Eng. J. 2017, 330, 1044-1051, DOI 10.1016/j.cej.2017.08.041. (13) Wirthl, D.; Pichler, R.; Drack, M.; Kettlguber, G.; Moser, R.; Gerstmayr, R.; Hartmann, F.; Bradt, E.; Kaltseis, R.; Siket, C. M.; Schausberger, S. E.; Hild, S.; Bauer, S.; Kaltenbrunner, M. Instant tough bonding of hydrogels for soft machines and electronics. Sci. Adv. 2017, 3 (6), e1700053, DOI

10.1126/sciadv.1700053.

(14) Jing, X.; Mi, H.-Y.; Peng, X.-F.; Turng, L.-S. Biocompatible, self-healing, highly stretchable polyacrylic acid/reduced graphene oxide nanocomposite hydrogel sensors via mussel-inspired chemistry. Carbon 2018, 136, 63-72, DOI 10.1016/j.carbon.2018.04.065. (15) Pu, X.; Liu, M.; Chen, X.; Sun, J.; Du, C.; Zhang, Y.; Zhai, J.; Hu, W.; Wang, Z. L. Ultrastretchable, transparent triboelectric nanogenerator as electronic skin for biomechanical energy

harvesting

and

tactile

sensing.

Sci.

Adv.

2017,

22


3

(5),

1700015,

DOI

Page 23 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


10.1126/sciadv.1700015. (16) Liu, T.; Liu, M.; Dou, S.; Sun, J.; Cong, Z.; Jiang, C.; Du, C.; Pu, X.; Hu, W.; Wang, Z. L. Triboelectric-Nanogenerator-Based Soft Energy-Harvesting Skin Enabled by Toughly Bonded Elastomer/Hydrogel

Hybrids.

ACS

Nano

2018,

12

(3),

2818-2826,

DOI

10.1021/acsnano.8b00108. (17) Han, L.; Yan, L.; Wang, M.; Wang, K.; Fang, L.; Zhou, J.; Fang, J.; Ren, F.; Lu, X. Transparent, Adhesive, and Conductive Hydrogel for Soft Bioelectronics Based on LightTransmitting Polydopamine-Doped Polypyrrole Nanofibrils. Chem. Mater. 2018, 30 (16), 55615572, DOI 10.1021/acs.chemmater.8b01446. (18) Liu, K.; Pan, X.; Chen, L.; Huang, L.; Ni, Y.; Liu, J.; Cao, S.; Wang, H. Ultrasoft Self-Healing Nanoparticle-Hydrogel Composites with Conductive and Magnetic Properties. ACS Sustainable

Chem. Eng. 2018, 6 (5), 6395-6403, DOI 10.1021/acssuschemeng.8b00193. (19) Liu, K.; Chen, L.; Huang, L.; Ni, Y.; Xu, Z.; Lin, S.; Wang, H. A facile preparation strategy for conductive and magnetic agarose hydrogels with reversible restorability composed of nanofibrillated cellulose, polypyrrole, and Fe3O4. Cellulose 2018, 25 (8), 4565-4575, DOI 10.1007/s10570-018-1889-x. (20) Roh, E.; Hwang, B.-U.; Kim, D.; Kim, B.-Y.; Lee, N.-E. Stretchable, Transparent, Ultrasensitive, and Patchable Strain Sensor for Human-Machine Interfaces Comprising a Nanohybrid of Carbon Nanotubes and Conductive Elastomers. ACS Nano 2015, 9 (6), 62526261, DOI 10.1021/acsnano.5b01613. (21) Cai, G.; Wang, J.; Qian, K.; Chen, J.; Li, S.; Lee, P. S. Extremely Stretchable Strain Sensors Based on Conductive Self-Healing Dynamic Cross-Links Hydrogels for Human-Motion 23



Detection. Adv. Sci. 2017, 4 (2) , 1600190, DOI 10.1002/advs.201600190. (22) Darabi, M. A.; Khosrozadeh, A.; Mbeleck, R.; Liu, Y.; Chang, Q.; Jiang, J.; Cai, J.; Wang, Q.; Luo, G.; Xing, M. Skin-Inspired Multifunctional Autonomic-Intrinsic Conductive Self-Healing Hydrogels with Pressure Sensitivity, Stretchability, and 3D Printability. Adv. Mater. 2018, 30 (4), 1705922, DOI 10.1002/adma.201700533. (23) Vaisman, L.; Marom, G.; Wagner, H. D. Dispersions of surface-modified carbon nanotubes in water-soluble and water-insoluble polymers. Adv. Funct. Mater. 2006, 16 (3), 357-363, DOI 10.1002/adfm.200500142. (24) Zhang, X.; Liu, M.; Zhang, X.; Deng, F.; Zhou, C.; Hui, J.; Liu, W.; Wei, Y. Interaction of tannic acid with carbon nanotubes: enhancement of dispersibility and biocompatibility. Toxicol.

Res. 2015, 4 (1), 160-168, DOI 10.1039/C4TX00066H. (25) Lin, D.; Xing, B. Tannic acid adsorption and its role for stabilizing carbon nanotube suspensions. Environ. Sci. Technol. 2008, 42 (16), 5917-5923, DOI 10.1021/es800329c. (26) Liu, M.; Zhang, X.; Yang, B.; Deng, F.; Huang, Z.; Yang, Y.; Li, Z.; Zhang, X.; Wei, Y. Ultrabright and biocompatible AIE dye based zwitterionic polymeric nanoparticles for biological imaging. RSC Adv. 2014, 4 (66), 35137-35143, DOI 10.1039/C4RA06160H. (27) Yang, C.; Suo, Z. Hydrogel ionotronics. Nat. Rev. Mater. 2018, 3 (6), 125-142, DOI 10.1038/s41578-018-0018-7. (28) Sun, J.-Y.; Keplinger, C.; Whitesides, G. M.; Suo, Z. Ionic Skin. Adv. Mater. 2014, 26 (45), 7608-7614, DOI 10.1002/adma.201403441. (29) Lei, Z.; Wang, Q.; Sun, S.; Zhu, W.; Wu, P. A Bioinspired Mineral Hydrogel as a SelfHealable, Mechanically Adaptable Ionic Skin for Highly Sensitive Pressure Sensing. Adv. Mater. 24


Page 24 of 31

Page 25 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2017, 29 (22),1700321, DOI 10.1002/adma.201700321 . (30) Lei, Z.; Wu, P. A supramolecular biomimetic skin combining a wide spectrum of mechanical properties and multiple sensory capabilities. Nat. Commun. 2018, 9, 1134, DOI https://doi.org/10.1038/s41467-018-03456-w. (31) Yuk, H.; Lu, B.; Zhao, X. Hydrogel bioelectronics.

Chem.Soc.Rev.2018,

DOI

10.1039/C8CS00595H. (32) Han, L.; Lu, X.; Wang, M.; Gan, D.; Deng, W.; Wang, K.; Fang, L.; Liu, K.; Chan, C. W.; Tang, Y.; Weng, L.-T.; Yuan, H. A Mussel-Inspired Conductive, Self-Adhesive, and SelfHealable Tough Hydrogel as Cell Stimulators and Implantable Bioelectronics. Small 2017, 13 (2), 1601916, DOI 10.1002/smll.201601916 . (33) Liu, S.; Zheng, R.; Chen, S.; Wu, Y.; Liu, H.; Wang, P.; Deng, Z.; Liu, L. A compliant, selfadhesive and self-healing wearable hydrogel as epidermal strain sensor. J. Mater. Chem. C 2018, 6 (15), 4183-4190, DOI 10.1039/C8TC00157J. (34) Son, D.; Kang, J.; Vardoulis, O.; Kim, Y.; Matsuhisa, N.; Oh, J. Y.; To, J. W. F.; Mun, J.; Katsumata, T.; Liu, Y.; McGuire, A. F.; Krason, M.; Molina-Lopez, F.; Ham, J.; Kraft, U.; Lee, Y.; Yun, Y.; Tok, J. B. H.; Bao, Z. An integrated self-healable electronic skin system fabricated via dynamic reconstruction of a nanostructured conducting network. Nat. Nanotechnol. 2018,

13 (11), 1057-1065, DOI 10.1038/s41565-018-0244-6. (35) Zou, Z.; Jang, A.; MacKnight, E.; Wu, P.-M.; Do, J.; Bishop, P. L.; Ahn, C. H. Environmentally friendly disposable sensors with microfabricated on-chip planar bismuth electrode for in situ heavy metal ions measurement. Sens. Actuators, B 2008, 134 (1), 18-24, DOI 10.1016/j.snb.2008.04.005. 25



Page 26 of 31

(36) Dai, L.; Long, Z.; Chen, J.; An, X.; Cheng, D.; Khan, A.; Ni, Y. Robust Guar Gum/Cellulose Nanofibrils Multilayer Films with Good Barrier Properties. ACS Appl. Mater. Interfaces 2017, 9 (6), 5477-5485, DOI 10.1021/acsami.6b14471. (37) Dai, L.; Nadeau, B.; An, X.; Cheng, D.; Long, Z.; Ni, Y. Silver nanoparticles-containing dual-function hydrogels based on a guar gum-sodium borohydride system. Sci. Rep. 2016,

6,36497, DOI 10.1038/srep36497. (38) Pan, X.; Wang, Q.; Ning, D.; Dai, L.; Liu, K.; Ni, Y.; Chen, L.; Huang, L. Ultraflexible SelfHealing Guar Gum-Glycerol Hydrogel with Injectable, Antifreeze, and Strain-Sensitive Properties.

ACS

Biomater.

Sci.

Eng.

2018,

4

(9),

3397-3404,

DOI

10.1021/acsbiomaterials.8b00657. (39) Jing, X.; Mi, H.-Y.; Lin, Y.-J.; Enriquez, E.; Peng, X.-F.; Turng, L.-S. Highly Stretchable and Biocompatible Strain Sensors Based on Mussel-Inspired Super-Adhesive Self-Healing Hydrogels for Human Motion Monitoring. ACS Appl. Mater. Interfaces 2018, 10 (24), 2089720909, DOI 10.1021/acsami.8b06475. (40) Pan, X.; Wang, Q.; Guo, R.; Ni, Y.; Liu, K.; Ouyang, X.; Chen, L.; Huang, L.; Cao, S.; Xie, M. An integrated transparent, UV-filtering organohydrogel sensor via molecular-level ion conductive channels. J. Mater. Chem.A 2019, 7, 4525-4535, DOI 10.1039/C8TA12360H. (41) Jeong, J.-W.; Kim, M. K.; Cheng, H.; Yeo, W.-H.; Huang, X.; Liu, Y.; Zhang, Y.; Huang, Y.; Rogers,

J.

A.

Capacitive

Epidermal

Electronics

for

Electrically

Safe,

Long-Term

Electrophysiological Measurements. Adv. Healthcare Mater. 2014, 3 (5), 642-648, DOI 10.1002/adhm.201300334. (42) Myers, A. C.; Huang, H.; Zhu, Y. Wearable silver nanowire dry electrodes for 26


Page 27 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


electrophysiological sensing. RSC Adv. 2015, 5 (15), 11627-11632, DOI 10.1039/C4RA15101A. (43) Han, L.; Yan, L.; Wang, K.; Fang, L.; Zhang, H.; Tang, Y.; Ding, Y.; Weng, L.-T.; Xu, J.; Weng, J.; Liu, Y.; Ren, F.; Lu, X. Tough, self-healable and tissue-adhesive hydrogel with tunable multifunctionality. NPG Asia Mater. 2017, 9, e372, DOI 10.1038/am.2017.33. (44) Han, L.; Lu, X.; Liu, K.; Wang, K.; Fang, L.; Weng, L.-T.; Zhang, H.; Tang, Y.; Ren, F.; Zhao, C.; Sun, G.; Liang, R.; Li, Z. Mussel-Inspired Adhesive and Tough Hydrogel Based on Nanoclay Confined Dopamine Polymerization. ACS Nano 2017, 11 (3), 2561-2574, DOI 10.1021/acsnano.6b05318 . (45) Sileika, T. S.; Barrett, D. G.; Zhang, R.; Lau, K. H. A.; Messersmith, P. B. Colorless Multifunctional Coatings Inspired by Polyphenols Found in Tea, Chocolate, and Wine. Angew.

Chem., Int. Ed. 2013, 52 (41), 10766-10770, DOI 10.1002/ange.201304922. (46) Shao, C.; Meng, L.; Wang, M.; Cui, C.; Wang, B.; Han, C.-R.; Xu, F.; Yang, J. Mimicking Dynamic Adhesiveness and Strain-Stiffening Behavior of Biological Tissues in Tough and SelfHealable Cellulose Nanocomposite Hydrogels. ACS Appl. Mater. Interfaces 2019, 11 (6), 58855895, DOI 10.1021/acsami.8b21588. (47) Shao, C.; Wang, M.; Meng, L.; Chang, H.; Wang, B.; Xu, F.; Wang, J.; Wan, P. MusselInspired Cellulose Nanocomposite Tough Hydrogels with Synergistic Self-Healing, Adhesive, and

Strain-Sensitive

Properties.

Chem.

Mater.

2018,

30

(9),

3110-3121,

DOI

10.1021/acs.chemmater.8b01172. (48) Chang, M. Y.; Juang, R. S. Adsorption of tannic acid, humic acid, and dyes from water using the composite of chitosan and activated clay. J. Colloid Interface Sci. 2004, 278 (1), 1825, DOI 10.1016/j.jcis.2004.05.029. 27



Page 28 of 31

(49) Li, W. G.; Zhang, X. Y.; Wu, Y. J.; Tian, X. Anti-inflammatory effect and mechanism of proanthocyanidins from grape seeds. Acta Pharmacol. Sin. 2001, 22 (12), 1117-1120 . (50) Liu, K.; Nasrallah, J.; Chen, L.; Huang, L.; Ni, Y.; Lin, S.; Wang, H. A facile template approach

to

preparing

multifunctionality

to

stable

paper.

NFC/Ag/polyaniline

Carbohydr.

Polym.

nanocomposites 2018,

194,

for

imparting

97-102,

DOI

10.1016/j.carbpol.2018.04.015. (51) Liu, K.; Chen, L.; Huang, L.; Ni, Y.; Sun, B. Enhancing antibacterium and strength of cellulosic paper by coating triclosan-loaded nanofibrillated cellulose (NFC). Carbohydr.Polym. 2015, 117, 996-1001, DOI 10.1016/j.carbpol.2014.10.014. (52) Liu, K.; Chen, L.; Huang, L.; Lai, Y. Evaluation of ethylenediamine-modified nanofibrillated cellulose/chitosan composites on adsorption of cationic and anionic dyes from aqueous solution.

Carbohydr. Polym. 2016, 151, 1115-1119, DOI 10.1016/j.carbpol.2016.06.071. (53) Saito, T.; Kimura, S.; Nishiyama, Y.; Isogai, A. Cellulose nanofibers prepared by TEMPOmediated oxidation of native cellulose. Biomacromolecules 2007, 8 (8), 2485-2491, DOI 10.1021/bm0703970. (54) Xu, X.-J.; Huang, S.-M.; Zhang, L.-H. Biodegradability, Antibacterial Properties, and Ultraviolet Protection of Polyvinyl Alcohol-Natural Polyphenol Blends. Polym. Compos. 2009,

30 (11), 1611-1617, DOI 10.1002/pc.20734. (55) Liu, Y. J.; Cao, W. T.; Ma, M. G.; Wan, P. Ultrasensitive Wearable Soft Strain Sensors of Conductive, Self-healing, and Elastic Hydrogels with Synergistic "Soft and Hard" Hybrid Networks.

ACS

Appl.

Mater.

Interfaces

2017,

10.1021/acsami.7b07639. 28


9

(30),25559-25570,

DOI

Page 29 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(56) Han, J.; Lu, K.; Yue, Y.; Mei, C.; Huang, C.; Wu, Q.; Xu, X. Nanocellulose-templated assembly of polyaniline in natural rubber-based hybrid elastomers toward flexible electronic conductors. Ind. Crops Prod. 2019, 128, 94-107, DOI 10.1016/j.indcrop.2018.11.004. (57) Liu, Y.; Pharr, M.; Salvatore, G. A. Lab-on-Skin: A Review of Flexible and Stretchable Electronics for Wearable Health Monitoring. ACS Nano 2017, 11 (10), 9614-9635, DOI 10.1021/acsnano.7b04898. (58) Kwon, Y.-T.; Kim, Y.-S.; Lee, Y.; Kwon, S.; Lim, M.; Song, Y.; Choa, Y.-H.; Yeo, W.-H. Ultrahigh Conductivity and Superior Interfacial Adhesion of a Nanostructured, Photonic Sintered Copper Membrane for Printed Flexible Hybrid Electronics.ACS Appl. Mater. Interfaces 2018, 10(50), 44071-44079, DOI 10.1021/acsami.8b17164 . (59) Guo, R.; Su, Q.; Zhang, J.; Dong, A.; Lin, C.; Zhang, J. Facile Access to Multisensitive and Self-Healing Hydrogels with Reversible and Dynamic Boronic Ester and Disulfide Linkages.

Biomacromolecules 2017, 18 (4), 1356-1364, DOI 10.1021/acs.biomac.7b00089. (60) Ding, Q.; Xu, X.; Yue, Y.; Mei, C.; Huang, C.; Jiang, S.; Wu, Q.; Han, J. NanocelluloseMediated

Electroconductive

Self-Healing

Hydrogels

with

High

Strength,

Plasticity,

Viscoelasticity, Stretchability, and Biocompatibility toward Multifunctional Applications. ACS

Appl. Mater. Interfaces 2018, 10 (33), 27987-28002, DOI 10.1021/acsami.8b09656.

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Green mussel-inspired cellulose nanocomposite hydrogels with adhesive, conductive, and injectable properties are prepared and used as reusable electrodes for human electrophysiological (EP) signals detection.

31


Mussel-inspired nanocomposite hydrogel-based electrodes with

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