Guanghui Gao

Bioinspired Adhesive Hydrogel Driven by Adenine and Thymine

Bioinspired strategies have drawn much attention for designing intelligent hydrogels with promising performance. Herein, we present a bioinspired adhesive hydrogel driven by adenine and thymine, which are the basic units of DNA. The adhesive hydrogel exhibited promising adhesive property for the surface of various solid materials, including muscle tissues, plastics, rubbers, glasses, metals, ceramics, carnelians, and woods. The maximum peeling strength of hydrogels was 330 N m-1 on aluminum, superior to that of PAAm hydrogels with 70 N m-1. The strong adhesive behavior remained more than 30 times repeated peeling tests. Moreover, the swelling behavior, morphological structure, mechanical strength, and peeling adhesive strength were also investigated and confirmed the formation and various characteristics of adhesive hydrogels driven by adenine and thymine. Thus, the biomimetic strategy to design promising adhesive hydrogels can provide various opportunities in tissue engineering, such as wound dressing, bioglues, and tissue adhesives.

The effect of hydrophobic alkyl chain length on the mechanical properties of latex particle hydrogels

Herein, different long alkyl chains (C1, C6, C12, and C16) were introduced as hydrophobic segments to enhance the performance of hydrogels reinforced by latex particles (LP-Gel). Poly(butyl acrylate) (PBA) latex particles (LPs) were employed as hydrophobic association cross-linking centers. First, the PBA latex particles were prepared via emulsion polymerization, and then, LP-Gel with high mechanical strength was prepared via one-pot free radical polymerization using acrylamide as a monomer, LP as a cross-linking center, and methacrylate as a hydrophobic molecule. It was found that the length of the hydrophobic alkyl chains from methacrylate has a significant effect on the mechanical performance and swelling degree of the hydrogels. The short alkyl chains exhibited weak hydrophobic interactions, and the resulting LP-Gel had a low mechanical strength. However, the long alkyl chains can effectively entangle with LPs through strong hydrophobic interactions, which significantly enhance the mechanical strength of the hydrogels. As a result, the LP-Gel exhibits a maximum fracture stress of 1.2 MPa and elongation of 2336%. This study will have a profound impact on the understanding of hydrogels toughened by hydrophobic alkyl chains of different lengths.

A rapidly responsive photochromic hydrogel with high mechanical strength for ink-free printing

Ink-free printing based on photochromism has attracted great attention as a new generation of printing technology. However, the current photochromic materials are limited due to slow response and high cost. In this investigation, a rapidly responsive photochromic hydrogel with high mechanical strength was explored through the introduction of cheap ammonium molybdate into gelatin and hydrophobic associative polyacrylamide. The photochromic hydrogel exhibited excellent mechanical strength of 750 kPa and a rapidly responsive photochromic process of 5 seconds with UV light irradiation. Moreover, the hydrogel could withstand long elongation and high compressive stress with shape recovery ability. The rapid photochromic properties gave hydrogels with fast and easy “printing” performance. More importantly, the “printed” text or pattern in hydrogels could be erased at 70 °C in an oxygen environment. In addition, the hydrogel could be written on in characters by using reducing reagents. Photochromic hydrogels with ink-free printing ability would demonstrate a new design strategy for soft materials with low-cost, rapid response and high mechanical properties.

Multipurpose and Durable Adhesive Hydrogel Assisted by Adenine and Uracil from Ribonucleic Acid

Nucleobase pairs of adenine and uracil (A-U) from ribonucleic acid are of particular interest for various promising material properties. Herein, a novel polyacrylamide hydrogel with adhesive properties that are assisted by adenine and uracil has been designed and investigated. The incorporation of adenine and uracil enables the formation of a polyacrylamide hydrogel with remarkable adhesive behaviour with various materials including polytetrafluoroethylene (PTFE), plastics, rubber, glasses, metal, ceramics and wood. Moreover, the adhesive hydrogel can easily and directly adhere to humid biological tissues without any extra process, including heart, liver, spleen, lung, kidney, bone and muscle of mouse. More impressively, even after repeated peeling tests (10×), the AU-mediated polyacrylamide hydrogel still exhibits excellent durable adhesion for various materials. From mechanical contact tests, the adhesion energy of the A-U adhesive hydrogel is 47.9u2005Ju2009m-2 , which is nearly nine times that of polyacrylamide hydrogel (5.3u2005Ju2009m-2 ). The 90° peeling strength for aluminium, titanium, silica rubbers, glasses, PTFE and hogskin is 518, 645, 445, 396, 349, and 119u2005Nu2009m-1 , respectively. The multipurpose and durable adhesive behaviour of hydrogels assisted by adenine and uracil indicated the promise of nucleobase pairs from ribonucleic acid for the future development of adhesive materials.

Tough, sticky and remoldable hydrophobic association hydrogel regulated by polysaccharide and sodium dodecyl sulfate as emulsifiers

Hydrophobic association hydrogels have been extensively studied during the past decades. However, the fracture stress of hydrophobic association hydrogels obtained with anionic surfactants (such as sodium dodecyl sulfate) achieved hundreds of Pascal. In this investigation, combined surfactants consisting of polysaccharide (gum arabic) and sodium dodecyl sulfate were utilized to stabilize hydrogels with high fracture stress of more than 1u2009MPa. Moreover, the hydrogels exhibited excellent self-healing capacity and remoldable behavior without any stimulation. Simultaneously, the hydrogels demonstrated an adhesive behavior for various solid substrates including polytetrafluoroethylene, plastics, rubbers, glasses, metals and woods. The hydrogel with toughness, self-healing, stickiness and remoldable properties would be expected to be applied in the medical fields, such as wound dressing, medical electrodes, tissue adhesives and portable equipment.

Low-Cost, Rapidly Responsive, Controllable, and Reversible Photochromic Hydrogel for Display and Storage

Traditional optoelectronic devices without stretchable performance could be limited for substrates with irregular shape. Therefore, it is urgent to explore a new generation of flexible, stretchable, and low-cost intelligent vehicles as visual display and storage devices, such as hydrogels. In the investigation, a novel photochromic hydrogel was developed by introducing the negatively charged ammonium molybdate as a photochromic unit into polyacrylamide via ionic and covalent cross-linking. The hydrogel exhibited excellent properties of low cost, easy preparation, stretchable deformation, fatigue resistance, high transparency, and second-order response to external signals. Moreover, the photochromic and fading process of hydrogels could be precisely controlled and repeated under the irradiation of UV light and exposure of oxygen at different time and temperature. The photochromic hydrogel could be considered applied for artificial intelligence system, wearable healthcare device, and flexible memory device. Therefore, the strategy for designing a soft photochromic material would open a new direction to manufacture flexible and stretchable devices.