Hydrogel Nanoarchitectonics of a Flexible and Self‐Adhesive Electrode for Long‐Term Wireless Electroencephalogram Recording and High‐Accuracy Sustained Attention Evaluation

Abstract

Hydrogels are ideal building blocks to fabricate the next generation of electrodes for acquiring high‐quality physiological electrical signals, for example, electroencephalography (EEG). However, collection of EEG signals still suffers from electrode deformation, sweating, extensive body motion and vibration, and environmental interference. Herein, polyvinyl alcohol and polyvinylpyrrolidone are selected to prepare a hydrogel network with tissue‐like modulus and excellent flexibility. Additionally, polydopamine nanoparticles, obtained by polydopamine peroxidation, are integrated into the hydrogel to endow them with higher transparency, higher self‐adhesion, and lower impedance. Consequently, a multichannel and wirelessly operated hydrogel electrode can establish a conformal and stable interface with tissue and illustrate high channel uniformity, low interfacial contact impedance, low power noise, long‐term stability, and a tolerance to sweat and motion. Furthermore, the hydrogel electrode shows the unprecedented ability to classify the recorded high‐quality prefrontal EEG signals into seven‐category sustained attention with high accuracy (91.5%), having great potential applications in the assessment of human consciousness and in multifunctional diagnoses.

Solvent‐Free and Skin‐Like Supramolecular Ion‐Conductive Elastomers with Versatile Processability for Multifunctional Ionic Tattoos and On‐Skin Bioelectronics

“…We show in Figure 6j the advantages of our I‐tattoo electrodes over the previously reported different types of skin electrodes, including the hydrogel electrodes, [ 36–39,74–78 ] sticker‐type E‐tattoo electrodes, [ 1,5,12–19,79–87 ] and paintable E‐tattoos. [ 20–24 ] It is worth noting that paintable hydrogels, obtained via the gelation of hot liquid precursors (60–75 °C) on human skin, were reported by Someya's group for monitoring electrophysiological signals.…”

“…The capture of the electrophysiological signals not only plays a vital role in clinical applications, but also is the key to construct humanmachine interfaces, which has become an active field with significant advances in non-clinical areas such as home/work automation, cognitive training, entertainment, and so forth. [18][19][20][21][22]39,[72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87] Our paintable I-tattoos, featuring exceptional stability and low electrode-skin IEI, are superb candidates as skin electrodes for the high-fidelity acquisition of various electrophysiological sig-nals. To monitor the ECG signals, I-tattoos were painted on the inner wrists of the right and left forearms of a volunteer, and the metal conductors were directly adhered to the I-tattoos without a cumbersome fixation system (Figure 6a).…”

Photoswitchable and Reversible Fluorescent Eutectogels for Conformal Information Encryption

“…Compared with the previously reported materials with adhesive property, the eutectogel possesses favorable comprehensive performance, as shown in Figure 4g and Table S2. [17,[48][49][50][51][52] Counterfeiting is a severe problem that not only causes huge economic loss, but also poses a threat to human health, such as pharmaceutical falsification. [53] Therefore, anticounterfeiting labels play an important role in improving security.…”

Skin-Inspired Patterned Hydrogel with Strain-Stiffening Capability for Strain Sensors

“…Biological skin can not only provide a protective layer for inner tissues but also perceive external stimuli and interact with our surrounding world. , Inspired by the multiple sensory capabilities of biological skins, significant endeavors have been devoted to exploring emerging applications of conductive flexible materials in electronic skins, − human–machine interfaces, − soft robots, , and wearable monitoring devices. − Noteworthily, the interface between electrodes and tissues frequently suffers from dynamic deformation, especially for epidermal bioelectronic devices. The inherent defects of flexible materials, such as low stretchability, high stiffness, and high hysteresis, can generate mechanical mismatch at the tissue–material interface, which adversely affects the sensibility of bioelectronic devices. − Therefore, flexible sensing materials that simultaneously mimic the sensory capabilities and softness of skin can form a high compliance at the tissue–material interface and enable sensitive perceptions of various external stimuli.…”