Graphene Oxide‐Templated Conductive and Redox‐Active Nanosheets Incorporated Hydrogels for Adhesive Bioelectronics

Abstract

2D conductive nanosheets are central to electronic applications because of their large surface areas and excellent electronic properties. However, tuning the multifunctions and hydrophilicity of conductive nanosheets are still challenging. Herein, a green strategy is developed for fabricating conductive, redox-active, water-soluble nanosheets via the self-assembly of poly(3,4-ethylenedioxythiophene) (PEDOT) on the polydopamine-reduced and sulfonated graphene oxide (PSGO) template. The conductivity and hydrophilicity of nanosheets are highly improved by PSGO. The nanosheets are redox active due to the abundant catechol groups and can be used as versatile nanofillers in developing conductive and adhesive hydrogels. The nanosheets create a mussel-inspired redox environment inside the hydrogel networks and endow the hydrogel with long-term and repeatable adhesiveness. This hydrogel is biocompatible and can be implanted for biosignals detection in vivo. This mussel-inspired strategy for assembling 2D nanosheets can be adapted for producing diverse multifunctional nanomaterials, with various potential applications in bioelectronics.because of their fascinating properties such as large surface areas, numerous active sites, and high conductivity and mechanical strength. [4] In particular, the emerging class of redox-active 2D conductive nanosheets such as covalent organic framework [5] and redox-active heteroatomloaded carbon nanosheets [6] has been used in various areas, e.g., catalysis, solar cells, photochemical water splitting, organic rechargeable battery cathodes, and bioelectronics. The common approach of fabricating conductive nanosheets via mechanical exfoliation lacks effective function tunability. Incorporation of inorganic redox couples such as transition-metal ions has frequently been used to make conductive nanosheets redox active. [7] However, these redox couples often involve toxic and precious-metal ions, and this hinders their biomedical applications. There is therefore an urgent need to develop green and costeffective approaches to fabricating biocompatible, redox-active, and conductive nanosheets for future bioelectronic and biomedical applications.Composites of conductive nanosheets and hydrogels are considered to be promising candidates for use in next-generation soft and flexible bioelectronics. [8] Poly(3,4-ethylenedioxythiophene) (PEDOT) is an ideal conductive material for flexible electronics because of its high electrical conductivity and excellent chemical stability. [9] However, because of the hydrophobicity and intrinsic chemical structure of PEDOT, the production of PEDOT nanosheets and their uniform dispersion in a hydrogel matrix is challenging. In addition, interfacial adhesion between the hydrogel and tissues is of critical importance, especially for electronic skin and implantable bioelectrode. [10] It is desire to develop flexible and tissue-adhesive bioelectronics so that they can tightly integrate with surrounding tissues. Recently, adhesive hydrogels based on mussel-inspired c...

Fully organic compliant dry electrodes self-adhesive to skin for long-term motion-robust epidermal biopotential monitoring

“…But they are difficult to handle, and high noise was observed during body movement. Apart from dry electrodes, conductive hydrogels were investigated as adhesive electrodes as well 68 . Because they are wet electrodes, the water vaporization from the hydrogels can induce signal decay and noise.…”

Mussel-inspired nanozyme catalyzed conductive and self-setting hydrogel for adhesive and antibacterial bioelectronics

“…Thus, abundant phenolic hydroxyl groups were retained inside the hydrogel, enabling long-term and repeatable adhesion of the hydrogel to various substrates via hydrogen bonding, coordination bonding, cation-π interactions, π-π interactions, and covalent linkage ( Fig. 4 e–iii) [ 64 ].…”

“…The currently available hydrogel bioelectronics lack multifunctional characteristics to fully adapt to biological environments. In particular, the lack of self-adhesiveness makes the hydrogel bioelectronics inconvenient and unstable for bio-signal detection, thereby necessitating external aids [ 5 , 6 ]. Hydrogels with strong adhesion capabilities can eliminate the need for external aids, facilitating comfortable wear experience, conformal contact with the tissues, and reliable and stable performance [ [7] , [8] , [9] ].…”

Strategic Advances in Spatiotemporal Control of Bioinspired Phenolic Chemistries in Materials Science

“…Reproduced with permission. [ 139 ] Copyright 2019, Wiley. g) Scheme of the in situ deactivation of catechol‐containing adhesive using electrochemistry.…”