Gelatin/polycrylamide double-network (DN) hydrogels composed of two different polymer networks with strong asymmetry are excellent structural platforms to integrate different mechanical properties into a single material.
Developing functional hybrids of globular proteins and synthetic polymers into multipurpose tough hydrogels remains challenging. Here, we propose a new strategy combining double-network and protein misfolding concepts to create diverse protein–polymer double-network (DN) hydrogels with both high bulk and interfacial toughness. The method integrates an intrinsic heat-induced protein denaturation/aggregation feature and a double-network concept, which produces different bovine serum albumin (BSA)-based DN hydrogels with hybrid physical–chemical cross-linking or fully physical cross-linking to achieve a high modulus of 252–1199 kPa, high strength of 0.24–0.48 MPa, high fracture energy of 3.56–16.88 MJ/m3, high extensibility of 7.7–79.9 mm/mm, fast self-recovery (stiffness/toughness recovery of 94/80% after heat treatment at 80 °C for 30 min), and strong surface adhesion to various nonporous solid surfaces (interfacial toughness of 1176–2827 J/m2). Such tough and adhesive protein–polymer hydrogels have great potential for different applications, such as artificial soft tissues, flexible electronics, and wearable devices.
Flexible electronics greatly facilitate human life due to their convenience and comfortable utilization. Liquid metals are an ideal candidate for flexible devices; however, the high surface tension and poor surface wettability restrict their application on diverse substrates. Herein, a printable and recyclable ink composed of poly(vinyl alcohol) and a liquid metal (PVA-LM) was developed to resolve these problems. The materials were designed considering the compatibility between PVA and the liquid metal, and the composite theory was applied to determine the component proportion. The developed composites improved the surface wettability of the liquid metal on diverse substrates, and three-dimensional (3D) printing technology was chosen to maximize the use of this material. Moreover, the PVA-LM ink showed excellent conductivity of about 1.3 × 105 S/m after being turned on, which favored the designing of alarm systems and object locators. The flexible sensors produced with this ink have broad application, high sensitivity, and superstable signal generation even after 200 cycles. When acting as strain sensors, the constructed composites had high sensitivity for monitoring the human movements. Furthermore, liquid metals in printed products can be recycled under alkaline conditions. This study opens a new direction for the next generation of environmentally friendly flexible devices.
Low-molecular-weight gelator (LMWG)-based supramolecular hydrogels, self-assembled by small molecules via noncovalent interactions, have recently attracted great attention due to their unique structure–property relationship and potential applications spanning from functional materials to biomedical devices. Unfortunately, many LMWG-based supramolecular hydrogels are mechanically weak and can not even be handled by conventional tensile and tearing tests. Here, we propose several design principles to fabricate new LMWG-based hydrogels with a true double-network structure (G4·K+/PDMAAm DN gels), consisting of the supramolecular self-assembly of guanosine, B(OH)3 and KOH as the first, physical G4·K+ network and the covalently cross-linked poly(N,N′-dimethyacrylamide) (PDMAAm) as the second, chemical network. Different from those LMWG-based supramolecular hydrogels, G4·K+/PDMAAm DN gels exhibit high tensile properties (elastic modulus = 0.307 MPa, tensile stress = 0.273 MPa, tensile strain = 17.62 mm/mm, and work of extension = 3.23 MJ/m3) and high toughness (tearing energies = 1640 J/m2). Meanwhile, the dynamic, noncovalent bonds in the G4·K+ network can reorganize and reform after being broken, resulting in rapid self-recovery property and excellent fatigue resistance. The stiffness/toughness of G4·K+/PDMAAm DN gels can be recovered by 65%/58% with 1 min resting at room temperature, and the recovery rates are further improved with the increase of temperatures and resting times. Interestingly, G4·K+/PDMAAm DN gels also exhibit UV-triggered luminescence due to the unique G4-quartet structure in the G4·K+ supramolecular first network. A new toughening mechanism is proposed to interpret the high strength and toughness of G4·K+/PDMAAm DN gels. We believe that our design principles, along with new G4·K+/PDMAAm DN gel system, will provide a new viewpoint for realizing the tough and strong LMWG-based gels.
Protein-based hydrogels have attracted great attention due to their excellent biocompatible properties, but often suffer from weak mechanical strength. Conventional strengthening strategies for protein-based hydrogels are to introduce nanoparticles or synthetic polymers for improving their mechanical strength, but often compromise their biocompatibility. Here, a new, general, protein unfolding-chemical coupling (PNC) strategy is developed to fabricate pure protein hydrogels without any additives to achieve both high mechanical strength and excellent cell biocompatibility. This PNC strategy combines thermal-induced protein unfolding/gelation to form a physically-crosslinked network and a -NH2/-COOH coupling reaction to generate a chemicallycrosslinked network. Using bovine serum albumin (BSA) as a globular protein, PNC-BSA hydrogels show macroscopic transparency, high stability, high mechanical properties (compressive/tensile strength of 115/0.43 MPa), fast stiffness/toughness recovery of 85%/91% at room temperature, good fatigue resistance, and low cell cytotoxicity and red blood cell hemolysis. More importantly, the PNC strategy can be not only generally applied to silk fibroin, ovalbumin, and milk albumin protein to form different, high strength protein hydrogels, but also modified with PEDOT/PSS nanoparticles as strain sensors and fluorescent fillers as color sensors. This work demonstrates a new, universal, PNC method to prepare high strength, multi-functional, pure protein hydrogels beyond a few available today.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.