Reversibly Stretchable Organohydrogel-Based Soft Electronics with Robust and Redox-Active Interfaces Enabled by Polyphenol-Incorporated Double Networks

Abstract

Hydrogel electrolytes as soft ionic conductors have been extensively exploited to establish skinlike and biocompatible devices. However, in many common hydrogels, there exists irreversible elongation upon prolonged stretching cycles and poor interfacial contact, which have significantly hindered their practical applications where long-term operation at large deformations is needed. Herein, multifunctional soft electronic devices with reversible stretchability and improved electrode/electrolyte interfaces are demonstrated by employing polyacrylamide-based double-network organohydrogel electrolytes soaked with a high content of tannic acid (TA) that affords multiple noncovalent interactions and redox activity. Performances of the TA-rich gels are evaluated for the first time in realizing shape-recoverable stretchable devices against repeated deformations to 500% strain, with superior gel−electrode interfaces exhibiting both intimate adhesion and boosted electrochemical capacitance of >200 mF•cm −2 . A maximal 4-fold higher capacitance can be achieved by introducing TA and ethylene glycol (EG) into hydrogels. Moreover, a soft electronic system consisting of stretchable supercapacitors and gel-based microsensors was demonstrated, in which the electronic performance of these devices can be well preserved after >1000 repeated cycles at strains of up to 200%, without obvious residual strain or electrode delamination. This could pave a route to the design of multifunctional gel networks tackling both the mechanical and interfacial issues in soft and biocompatible devices.

High-Transconductance, Highly Elastic, Durable and Recyclable All-Polymer Electrochemical Transistors with 3D Micro-Engineered Interfaces

“…This slight change may be a consequence of the suppressed irreversible elongation after cyclic stretching (< 25% residual strain) by taking advantage of the self-recovery characteristics of the noncovalently crosslinked gel networks (Fig. S1) [ 47 ]. Impedance measurement of GEL-GLY/Na 3 Cit was further performed to determine both the internal ion conductivity and the capacitance of the solid-state electrolyte (Fig.…”

High-Transconductance, Highly Elastic, Durable and Recyclable All-Polymer Electrochemical Transistors with 3D Micro-engineered Interfaces

“…The slight change could be a consequence of the suppressed irreversible elongation after cyclic stretching (< 25% residual strain) by the self-recovery of the non-covalently crosslinked gel networks (Figure S1). [41] Impedance measurement of GEL-GLY/Na 3 Cit was further performed to determine the internal ion conductivity and capacitance of the solid-state electrolyte (Fig. 2D).…”

Patterning meets gels: Advances in engineering functional gels at micro/nanoscales for soft devices

“…For carbon electrodes, Wang et al recently demonstrated that organohydrogels with tannic-acid-modified interfaces could enable robust adhesion of transfer printed serpentine microelectrodes to sustain thousands of stretching cycles at 100% strain, while the electrochemical capacitance could also be enhanced to ~4 folds owing to the redox activity of tannic acid. 117 In addition, the instant attachment of electrodes on prestretched hydrogels was facilitated by simply coating commercial cyanoacrylatebased adhesives, leading to tough bonding of various soft devices including integrated circuits, sensors, battery and drug-releasing device with high tension stability. 118 Alternatively, the conductive inks for fabricating microelectrodes can be directed printed onto the gel surface with stencil or ink-jet printing.…”

“… 116 The acidic solution of the Fe 3+ ‐containing precursors simultaneously promoted the rapid release of sacrificial PAA layer, accomplishing the aqueous‐phase transfer printing of polymer‐supported metal electrodes for neural interfaces. For carbon electrodes, Wang et al recently demonstrated that organohydrogels with tannic‐acid‐modified interfaces could enable robust adhesion of transfer printed serpentine microelectrodes to sustain thousands of stretching cycles at 100% strain, while the electrochemical capacitance could also be enhanced to ~4 folds owing to the redox activity of tannic acid 117 . In addition, the instant attachment of electrodes on prestretched hydrogels was facilitated by simply coating commercial cyanoacrylate‐based adhesives, leading to tough bonding of various soft devices including integrated circuits, sensors, battery and drug‐releasing device with high tension stability 118 …”