Conformal electrodes for on‐skin digitalization

Abstract

On‐skin digitalization, streamlining the concept of the “human to device to cyberspace” platform, has attracted great attention due to its vital function in remote medicine and human–cyber interfaces. Beyond traditional rigid electrodes, soft electrodes with conformal and comfortable interfaces are essential for long‐term and high‐fidelity signal acquisition. In addition, the on‐skin data processing systems will get rid of complex cables toward a vision of fascinating form, being lightweight, skin‐friendly and even imperceptible. Although numerous soft materials and devices with mechanical tolerance have been developed, the study of conformal electrodes and on‐skin digital integrated systems are still in infancy. Here, the requirements and designs of conformal electrodes, the emerging opportunities and challenges from multichannel/multifunctional sensors to a whole new on‐skin sensing platform are highlighted.

Strategies for interface issues and challenges of neural electrodes

“…Alternately, PEDOT is more favored than PPy due to the following factors: (i) PEDOT has a narrow band gap, 217 which promotes the shift of charges in the polymer chain; (ii) PEDOT has higher conductivity, which facilitates the preparation of neural electrodes with better electrical activity; 55,67,218 (iii) it has higher electrochemical stability, which is essential for obtaining a stable signal; 219–221 and (iv) PEDOT reveals better biocompatibility than PPy, which is an indispensable requirement for practical applications. 222–225 By adopting PEDOT:PSS as a conductive material, Blau et al 226 prepared an extendable and non-cytotoxic all-polymer electrode array. This electrode showed good stability in capturing muscle's action potential in vivo .…”

3D-printed flexible supercapacitors with multi-level bonded configuration via ion cross-linking

“…1–7 To efficiently power these advanced electronic systems, corresponding energy storage devices that can maintain high electrochemical performance under arbitrary mechanical deformation are desperately required. 8–13 Owing to the exceptional power density and long cycling lifetimes, supercapacitors are regarded as promising candidates for deformable and stretchable energy storage devices, but their performance is still far from satisfactory. 14–21…”

“…[1][2][3][4][5][6][7] To efficiently power these advanced electronic systems, corresponding energy storage devices that can maintain high electrochemical performance under arbitrary mechanical deformation are desperately required. [8][9][10][11][12][13] Owing to the exceptional power density and long cycling lifetimes, supercapacitors are regarded as promising candidates for deformable and stretchable energy storage devices, but their performance is still far from satisfactory. [14][15][16][17][18][19][20][21] To improve the deformable capability of the supercapacitors, research efforts have been carried out from both material and conguration perspectives.…”

Highly Conformal Polymers for Ambulatory Electrophysiological Sensing

“…Ambulatory electrophysiological sensing, including electrocardiogram (ECG), electromyogram (EMG), electroencephalogram (EEG), and electrooculography (EOG), reflects abundant bioelectric signals of human in the dynamic physiological activities. [1][2][3][4][5][6] The enduring stability of long-term ambulatory electrophysiological sensing opens a sensory window to capture multidimensional physiological parameters related to human health. [7][8][9][10] It offers great potential in the fields of smart e-healthcare monitoring, [11][12][13][14] clinical diagnosis of cardiovascular diseases, [15][16][17][18] treatment of neurological diseases, [19][20][21] and intelligent human-machine interaction.…”

“…[64][65][66] Therefore, highly conformal polymers are attracting wide attention of researchers in the field of ambulatory electrophysiological sensing. [1,28,44] So far, a variety of conformal polymers such as nature silk fibroin based conformal polymers, marine mussels bioinspired conformal polymers, and other conformal polymers including zwitterionic polymers and polyacrylamide have been designed and fabricated for ambulatory electrophysiological sensing. [67][68][69] However, most of current highly conformal polymers for on-skin electrodes have some issues such as high cost, complex synthesis process, unsatisfactory reusability, and difficulty in removing from skin, which largely limits the further development and application prospects in the future.…”