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Performance evaluation of on‐skin hydrogel devices. A) Schematics of the hydrogel device/skin interface (i), electromyography conduction on nerves (ii), and transmission of action potentials between nerve fibers (iii) during stimulation and recording processes. B,C) Charge injection curves (B) and cyclic voltammetry curves (C) of the commercial stimulation electrode, polyaspartic acid‐modified dopamine/ethyl‐based ionic liquid hydrogel (PDEH) silver‐liquid metal (SLM) device, and SLM device. D) Comparison of skin contact impedance between PDEH‐SLM devices, PDH‐SLM devices, and commercial gel electrodes. E) surface electromyography (sEMG) and corresponding signal‐to‐noise ratio (SNR) of commercial gel electrodes (original), PDEH‐SLM patches (original), and PDEH‐SLM patches (skin: under 20% strain). F) Photos of the commercial electrode (top) and PDEH‐SLM patch (original, bottom) attached to the large‐curvature thumb (i); Photographs show that the commercial electrode (top) causes much more excessive adhesion to skin hair, compared with the PDEH‐SLM patch (+4 V 5 s, bottom) (ii). G) Raw electromyography captured from large‐curvature thumb (median nerve, i) and hairy skin (deep peroneal nerve, ii). H,I) Corresponding SNRs of commercial electrodes and PDEH‐SLM patches (original/+4 V 5 s). J) The impact of PDEH/PDEH (+4 V) on human immortalized keratinocyte (HaCaT) death. Immunofluorescence staining with calcein‐AM (live cells, green) and propidium iodide (PI) (dead cells, red). (K and L) Rv (K) and Rp (L) of HaCaTs cultured in PDEH/PDEH (+4 V) incubated high‐glucose Dulbecco's modified Eagle's medium (HG‐DMEM) detected by CCK‐8 assay. p values are determined by two‐sided Student's t‐test between two groups and ANOVA with Tukey's post hoc test between multiple groups, respectively; *p < 0.05; ***p ≤ 0.001; ns, not significant. Data in (H), (I), (K), and (L) are presented as means ± SD, n = 3. Scale bars, 20 mm (E), 10 mm (F(i)), 5 mm (F(ii)), and 100 µm (J).
Source publication
Peripheral neuropathy characterized by rapidly increasing numbers of patients is commonly diagnosed via analyzing electromyography signals obtained from stimulation‐recording devices. However, existing commercial electrodes have difficulty in implementing conformal contact with skin and gentle detachment, dramatically impairing stimulation/recordin...
Citations
... (3D) tissue-like network structure, and tunable conducting sensing channels. [14][15][16][17] In the meantime, the epidermic sensors based on conductive hydrogels that are capable of converting external stimuli into detectable electrical signals, have received considerable attention in the fields of smart electronic skins, [18][19][20] medical diagnostics, [21][22][23][24] and human-machine interface. [25][26][27] Nevertheless, the mostly reported conductive hydrogel-based epidermic sensors commonly displayed high interfacial impedance, low conductivity, and restricted sensing performance from poor interfacial contact between skin and sensor. ...
Wearable epidermic electronics assembled from conductive hydrogels are attracting various research attention for their seamless integration with human body for conformally real‐time health monitoring, clinical diagnostics and medical treatment, and human‐interactive sensing. Nevertheless, it remains a tremendous challenge to simultaneously achieve conformally bioadhesive epidermic electronics with remarkable self‐adhesiveness, reliable ultraviolet (UV) protection ability, and admirable sensing performance for high‐fidelity epidermal electrophysiological signals monitoring, along with timely photothermal therapeutic performances after medical diagnostic sensing, as well as efficient antibacterial activity and reliable hemostatic effect for potential medical therapy. Herein, a conformally bioadhesive hydrogel‐based epidermic sensor, featuring superior self‐adhesiveness and excellent UV‐protection performance, is developed by dexterously assembling conducting MXene nanosheets network with biological hydrogel polymer network for conformally stably attaching onto human skin for high‐quality recording of various epidermal electrophysiological signals with high signal‐to‐noise ratios (SNR) and low interfacial impedance for intelligent medical diagnosis and smart human‐machine interface. Moreover, a smart sign language gesture recognition platform based on collected electromyogram (EMG) signals is designed for hassle‐free communication with hearing‐impaired people with the help of advanced machine learning algorithms. Meanwhile, the bioadhesive MXene hydrogel possesses reliable antibacterial capability, excellent biocompatibility, and effective hemostasis properties for promising bacterial‐infected wound bleeding.
... They also show promise due to their capability to add adhesion property during the synthetic process 104 . Yang et al. developed a polyaspartic acid-modified dopamine/ ethyl-based ionic liquid hydrogel as stimulation/recording device that can regulate its adhesion characteristic with a simple electric field treatment (Fig. 4c) 105 . Ten et al. developed a self-adhesive conductive polymer (SACP) composite for soft electronics by doping the rigid and non-stick PEDOT:PSS composites with a biocompatible supramolecular solvent (SMS) 106 . ...
Wearable skin-contacting devices are extensively studied for their ability to provide convenient and safe health monitoring. A key aspect that controls their performance are the properties of the device electrodes. Optimizing electrode structure, and the materials they are made from, can improve device functionality. Here, we discuss the various properties required for optimal electrode performance, including mechanical, electrical, and biocompatible factors. To address these challenges, we consider alteration of electrode structure, the development of flexible or soft conductive materials, and the creation of hybrid structures. Additionally, the integration of artificial intelligence is proposed as a promising direction to achieve smart devices. As well as outlining essential characteristics for high-performance wearable skin devices we also offer insight into possible future applications.
... Electronic skin has emerged as a pivotal component for the perception and sophisticated applications of robotics, such as prosthetics, surgical robots, advanced manufacturing, and autonomous environmental exploration. [1][2][3][4][5][6][7][8][9] Over the years, myriads of tactile sensors have been proposed for robots based on capacitive, [10,11] piezoresistive, [12,13] optical, [14,15] magnetic, [16] ionic, [17] and other sensing mechanisms. [4] These tactile sensors have been successfully proven beneficial for robots by providing feedback signals to them for object recognition and manipulation. ...
Active sensing is a fundamental aspect of human and animal interactions with the environment, providing essential information about the hardness, texture, and tackiness of objects. This ability stems from the presence of diverse mechanoreceptors in the skin, capable of detecting a wide range of stimuli and from the sensorimotor control of biological mechanisms. In contrast, existing tactile sensors for robotic applications typically excel in identifying only limited types of information, lacking the versatility of biological mechanoreceptors and the requisite sensing strategies to extract tactile information proactively. Here, inspired by human haptic perception, a skin‐inspired artificial 3D mechanoreceptor (SENS) capable of detecting multiple mechanical stimuli is developed to bridge sensing and action in a closed‐loop sensorimotor system for dynamic haptic exploration. A tensor‐based non‐linear theoretical model is established to characterize the 3D deformation (e.g., tensile, compressive, and shear deformation) of SENS, providing guidance for the design and optimization of multimode sensing properties with high fidelity. Based on SENS, a closed‐loop robotic system capable of recognizing objects with improved accuracy (≈96%) is further demonstrated. This dynamic haptic exploration approach shows promise for a wide range of applications such as autonomous learning, healthcare, and space and deep‐sea exploration.
... With an increasing focus on personal health, using hydrogel sensors for the real-time monitoring of physiological activities (such as pulse, respiration, and heartbeat) has become a hot topic, and the data collected can be used for the early diagnosis of diseases. Wu et al. [110] developed a polyaspartic acid-modified dopamine/ethyl ionic liquid hydrogel (PDEH). By further embedding a silver liquid metal (SLM) conductive layer to create PDEH-SLM patches, they could capture electromyographic signals for diagnosing peripheral neuropathies. ...
... With an increasing focus on personal health, using hydrogel sensors for the real-time monitoring of physiological activities (such as pulse, respiration, and heartbeat) has become a hot topic, and the data collected can be used for the early diagnosis of diseases. Wu et al. [110] developed a polyaspartic acid-modified dopamine/ethyl ionic liquid Various flexible epidermal sensors based on conductive hydrogels have made great progress in human health monitoring. However, the development of integrated health devices that combine reliable, sensitive diagnostic properties and timely treatment remains a great challenge in the wearable sensor field. ...
Conductive hydrogels, characterized by their excellent conductivity and flexibility, have attracted widespread attention and research in the field of flexible wearable sensors. This paper reviews the application progress, related challenges, and future prospects of conductive hydrogels in flexible wearable sensors. Initially, the basic properties and classifications of conductive hydrogels are introduced. Subsequently, this paper discusses in detail the specific applications of conductive hydrogels in different sensor applications, such as motion detection, medical diagnostics, electronic skin, and human–computer interactions. Finally, the application prospects and challenges are summarized. Overall, the exceptional performance and multifunctionality of conductive hydrogels make them one of the most important materials for future wearable technologies. However, further research and innovation are needed to overcome the challenges faced and to realize the wider application of conductive hydrogels in flexible sensors.
... [24,25,29,[31][32][33][34][35] Inspired by mussels, which exhibit strong adhesion in marine environments, hydrogels, and elastomers with dopamine or dopamine-like chemicals are widely used for the strong selfadhesion of E-skins. [32][33][34][36][37][38] The peeling adhesion of musselinspired E-skins showed higher adhesion than the commercial tapes. [32,34] Even more, by incorporating active groups like ─COO − and NHS ester to form covalent bonds with ─NH 2 groups in the human skin, E-skins with significantly stronger adhesion than commercial medical tapes have been developed. ...
... The skin adhesives that can be easily switched off are usually insufficient in adhesion strength. [30,38] Van der Waals force, which is www.advancedsciencenews.com www.afm-journal.de widely employed in commercial tapes, is one of the ideal candidates for skin adhesion as its easy manipulation. ...
The interfacial design of the electronic skins (E‐skins), which are increasingly crucial in areas like exercise monitoring, healthcare, etc., has a great impact on wearability and functions. The adhesion between E‐skin and human skin serves as the foundation for various functionalities. In addition to robust adhesion strength, detaching‐on‐demand, and waterproof abilities are also important for long‐time wearing and comfort detachment after use. Here, self‐adhesive, detach‐on‐demand, and waterproof hydrophobic E‐skins (PBIA) by copolymerization of acrylates with conductive ionic liquid and adhesive components as the strain sensor and triboelectric nanogenerator (TENG) is developed. The strong van der Waals self‐adhesion (shear adhesion of ≈574 kPa, peeling adhesion of ≈110 N m⁻¹), and waterproof abilities under immersing, flushing, and penetrating situations enable the E‐skin to realize stable and long‐time monitoring for body motions in both the resistance sensing and TENG modes. Meanwhile, the easy detach‐on‐demand ability of van der Waals adhesion (574 to 35 kPa and 110 to 7 N m⁻¹) guarantees the easy and comfortable detachment of PBIA after use, avoiding pain or injury to the skin. The adhesion strategy of PBIA can be expanded to other kinds of E‐skins and accelerate the pace of practical applications of E‐skins.
