Mussel-Bioinspired Lignin Adhesive for Wearable Bioelectrodes.

As a natural "binder," lignin fixes cellulose in plants to foster growth and longevity. However, isolated lignin has a poor binding ability, which limits its biomedical applications. In this study, inspired by mussel adhesive proteins, acidic/basic amino acids (AAs) are introduced in alkali lignin (AL) to form ionic-π/spatial correlation interactions, followed by demethylation to create catechol residues for enhanced adhesion activity. Atomic force microscopy reveals that catechol residues are the primary adhesion structures, with basic AAs exhibiting superior synergistic effects compared to acidic AAs. Demethylated lysine-grafted AL exhibits the strongest adhesion force toward skin tissue. Molecular dynamic simulation and density functional theory calculations indicate that adhesion against skin tissue mainly results from hydrogen bonds and cation-π interactions, with the adhesion mechanism being based on the Gibbs free energy of the Schiff base reaction. In summary, a biomimetic electrode based on lignin inspired by mussel adhesive proteins is prepared; the presented method offers a straightforward strategy for the development of biomimetic adhesives. Furthermore, this mussel-inspired adhesive can be used as a wearable bioelectrode in biomedical applications.

Highly tough and ionic conductive starch/poly(vinyl alcohol) hydrogels based on a universal soaking strategy.

High-performance hydrogels with favorable mechanical strength, high modulus, sufficient ionic conductivity and freezing resistance have far-ranging applications in flexible electronic equipment. Nevertheless, it is challenging to combine admirable mechanical properties and high ionic conductivity into one hydrogel. Herein, a facile strategy was developed for the preparation of the hydrogel with excellent strength (1.45 MPa), super Young's modulus (8.85 MPa) and high conductivity (1.47 S/m) using starch and poly(vinyl alcohol) (PVA) as raw materials. The starch/PVA/Gly/Na3Cit (SPGN) gel was firstly cross-linked by crystalline regions of PVA upon freezing-thawing cycles. It was further immersed in the saturated Na3Cit solution to enhance the interaction between the substrates through the salting-out effect. The effect of soaking time on the crystallinity, intermolecular interactions, mechanical and electrical properties of SPGN gel was demonstrated by X-ray diffraction, Fourier transform infrared spectroscopy, tensile and impedance testing measurements. The introduction of glycerol and Na3Cit also endowed SPGN gels with favorable anti-freezing properties. The SPGN gel could maintain high mechanical flexibility and ionic conductivity at -15 °C.

A facile preparation method for anti-freezing, tough, transparent, conductive and thermoplastic poly(vinyl alcohol)/sodium alginate/glycerol organohydrogel electrolyte.

Facile preparation of organohydrogel electrolyte integrated with good anti-freezing property, toughness, transparency, conductivity and thermoplasticity is important and still remains challenging. Novel conductive and tough poly(vinyl alcohol)/sodium alginate/glycerol (PVA/SA/Gly) composite organohydrogel electrolytes were obtained by a simple method in this paper. PVA and SA was firstly dissolved in a mixed solution of distilled water and glycerol and the PVA/SA/Gly organohydrogel was obtained by the freezing-thawing process, then PVA/SA/Gly organohydrogel was immersed into the saturated NaCl aqueous solution. During the soaking process NaCl would enter into the PVA/SA/Gly organohydrogel to increase the gel strength and conductivity. The PVA/SA/Gly organohydrogel electrolytes performed the high toughness with the tensile strength and elongation at break of 1.43 MPa and 558%, respectively. Moreover, the PVA/SA/Gly organohydrogel electrolytes behaved high transparency, anti-freezing property, conductivity and thermoplasticity due to the incorporation of glycerol. This paper provides a new preparation method for the high-performance organohydrogel electrolyte.