A General Synthesis Method for Patterning PEDOT toward Wearable Electronics and Bioelectronics.

The conductive polymer poly-3,4-ethylenedioxythiophene (PEDOT), recognized for its superior electrical conductivity and biocompatibility, has become an attractive material for developing wearable technologies and bioelectronics. Nevertheless, the complexities associated with PEDOT's patterning synthesis on diverse substrates persist despite recent technological progress. In this study, we introduce a novel deep eutectic solvent (DES)-induced vapor phase polymerization technique, facilitating nonrestrictive patterning polymerization of PEDOT across diverse substrates. By controlling the quantity of DES adsorbed per unit area on the substrates, PEDOT can be effectively patternized on cellulose, wood, plastic, glass, and even hydrogels. The resultant patterned PEDOT exhibits numerous benefits, such as an impressive electronic conductivity of 282 S·m-1, a high specific surface area of 5.29 m2·g-1, and an extensive electrochemical stability range from -1.4 to 2.4 V in a phosphate-buffered saline. To underscore the practicality and diverse applications of this DES-induced approach, we present multiple examples emphasizing its integration into self-supporting flexible electrodes, neuroelectrode interfaces, and precision circuit repair methodologies.

Bio-Inspired Multiscale Design for Strong and Tough Biological Ionogels.

Structure design provides an effective solution to develop advanced soft materials with desirable mechanical properties. However, creating multiscale structures in ionogels to obtain strong mechanical properties is challenging. Here, an in situ integration strategy for producing a multiscale-structured ionogel (M-gel) via ionothermal-stimulated silk fiber splitting and moderate molecularization in the cellulose-ions matrix is reported. The produced M-gel shows a multiscale structural superiority comprised of microfibers, nanofibrils, and supramolecular networks. When this strategy is used to construct a hexactinellid inspired M-gel, the resultant biomimetic M-gel shows excellent mechanical properties including elastic modulus of 31.5 MPa, fracture strength of 6.52 MPa, toughness reaching 1540 kJ m-3 , and instantaneous impact resistance of 3.07 kJ m-1 , which are comparable to those of most previously reported polymeric gels and even hardwood. This strategy is generalizable to other biopolymers, offering a promising in situ design method for biological ionogels that can be expanded to more demanding load-bearing materials requiring greater impact resistance.

A Scalable Bacterial Cellulose Ionogel for Multisensory Electronic Skin.

Electronic skin (e-skin), a new generation of flexible electronics, has drawn interest in soft robotics, artificial intelligence, and biomedical devices. However, most existing e-skins involve complex preparation procedures and are characterized by single-sensing capability and insufficient scalability. Here, we report on a one-step strategy in which a thermionic source is used for the in situ molecularization of bacterial cellulose polymeric fibers into molecular chains, controllably constructing an ionogel with a scalable mode for e-skin. The synergistic effect of a molecular-scale hydrogen bond interweaving network and a nanoscale fiber skeleton confers a robust tensile strength (up to 7.8 MPa) and high ionic conductivity (up to 62.58 mS/cm) on the as-developed ionogel. Inspired by the tongue to engineer the perceptual patterns in this ionogel, we present a smart e-skin with the perfect combination of excellent ion transport and discriminability, showing six stimulating responses to pressure, touch, temperature, humidity, magnetic force, and even astringency. This study proposes a simple, efficient, controllable, and sustainable approach toward a low-carbon, versatile, and scalable e-skin design and structure-performance development.

Developing cellulosic functional materials from multi-scale strategy and applications in flexible bioelectronic devices.

With the forthcoming of the post-COVID-19 and the ageing era, the novel biomaterials and bioelectronic devices are attracting more and more attention and favor. Cellulose as one of the most globe-abundant natural macromolecules has multiple merits of biocompatibility, processability, carbon neutral feature and mechanical designability. Due to its progressive advancement of multi-scale design from macro to micro followed by new cognitions, cellulose shows a promising application prospect in developing bio-functional materials. In this review, we briefly discuss the role of cellulose from the "top-down" perspective of macro-scale fibers, micro-scale nanofibers, and molecular-scale macromolecular chains for the design of advanced cellulose-based functional materials. The focus then turns to the construction and development of emerging cellulose-based flexible bioelectronic devices including biosensors, biomimetic electronic skins, and biological detection devices. Finally, the dilemma and challenge of cellulose-based bioelectronic materials and their application prospects in basic biology and medical care have been prospected.

A Stiffness-Switchable, Biomimetic Smart Material Enabled by Supramolecular Reconfiguration.

In nature, stiffness-changing behavior is essential for living organisms, which, however, is challenging to achieve in synthetic materials. Here, a stiffness-changing smart material, through developing interchangeable supramolecular configurations inspired from the dermis of the sea cucumber, which shows extreme, switchable mechanical properties, is reported. In the hydrated state, the material, possessing a stretched, double-stranded supramolecular network, showcases a soft-gel behavior with a low stiffness and high pliability. Upon the stimulation of ethanol to transform into the coiled supramolecular configuration, it self-adjusts to a hard state with nearly 500-times enhanced stiffness from 0.51 to 243.6 MPa, outstanding load-bearing capability (over 35 000 times its own weight), and excellent puncture/impact resistance with a specific impact strength of ≈116 kJ m-2 (g cm-3 )-1 (higher than some metals and alloys such as aluminum, and even comparable to the commercially available protective materials such as D3O and Kevlar). Moreover, this material demonstrates reconfiguration-dependent self-healing behavior and designable formability, holding great promise in advanced engineering fields that require both high-strength durability and good formability. This work may open up a new perspective for the development of self-regulating materials from supramolecular-scale configuration regulation.

Cellulose-Based Flexible Functional Materials for Emerging Intelligent Electronics.

There is currently enormous and growing demand for flexible electronics for personalized mobile equipment, human-machine interface units, wearable medical-healthcare systems, and bionic intelligent robots. Cellulose is a well-known natural biopolymer that has multiple advantages including low cost, renewability, easy processability, and biodegradability, as well as appealing mechanical performance, dielectricity, piezoelectricity, and convertibility. Because of its multiple merits, cellulose is frequently used as a substrate, binder, dielectric layer, gel electrolyte, and derived carbon material for flexible electronic devices. Leveraging the advantages of cellulose to design advanced functional materials will have a significant impact on portable intelligent electronics. Herein, the unique molecular structure and nanostructures (nanocrystals, nanofibers, nanosheets, etc.) of cellulose are briefly introduced, the structure-property-application relationships of cellulosic materials summarized, and the processing technologies for fabricating cellulose-based flexible electronics considered. The focus then turns to the recent advances of cellulose-based functional materials toward emerging intelligent electronic devices including flexible sensors, optoelectronic devices, field-effect transistors, nanogenerators, electrochemical energy storage devices, biomimetic electronic skins, and biological detection devices. Finally, an outlook of the potential challenges and future prospects for developing cellulose-based wearable devices and bioelectronic systems is presented.