Recent Advances on Designs and Applications of Hydrogel Adhesives

Abstract

extracellular matrix properties, gives them popularity in applications ranging from drug delivery, [4,5] wound dressing, [6][7][8] and tissue repair. [9,10] Various hydrogels with extraordinary properties have been reported, like tough, [11] stimuliresponse, [12] and optical variable hydrogels. [13] For example, the combination of covalently and ionically cross-linked networks endows hydrogel's excellent mechanical properties, achieving a value of 9000 J m −2 , which is comparable to natural rubber (10 000 J m −2 ). [11] Moreover, hydrogels with "self-growing" property [14] can stand duplicated stretch without ruption but gain a gradual increase in stress instead. However, in contrast to the bulk hydrogel, existing hydrogel adhesives are far from the desired properties. [15] The adhesion energy of commercial adhesives is usually ≈10 J m −2 compared to that of cartilage, composing a robust matrix of 1000 J m −2 and the adhesive layer of 800 J m −2 , respectively. [16] It is worth noting that medical and clinic adhesives should effectively prevent blood loss, gas, and tissue fluids leakage or exposure to the infectious environment or digestive fluids. [17] Thus, adhesion failure ought to result in negative therapy. Adhesion conductive hydrogels are also required to get skinlevel sensitive sensors since any interfacial vacant space will give rise to inaccurate signals. [18,19] As a result, sensors with high resolution and excellent accuracy can not be obtained under such circumstances due to "dead" regions. [20] Therefore, tough interactions between hydrogels matrix and diverse substrate, especially for wet tissues, are vital but challenging issues. [15] Of particularly significant and ideal properties for tough adhesives under stretching, dissipative energy within hydrogel matrix and interactive energy between interfaces is desired to prevent macroscopic movement. [21] By enhancing interfacial interactions via surface chemical modification, surface structuralizing, physical interlocks, or combining the principles mentioned above, a series of adhesive patches or tough adhesives with injectable, tunable curing time, degradable properties have been obtained.Numerous synthetic or natural materials, diverse design strategies, various methods, and many potential applications have emerged. In this review, as shown in Figure 1, we will summarize the state-of-art hydrogel adhesives spanning from design principles, including physical and chemical interactions In virtue of extracellular features, hydrogels have been used in various areas such as tissue repair, artificial skins, and biological electronics, etc. Intact contact of tough hydrogels to targeted surfaces is usually required to avoid blood or body fluids leakage or inaccurate signals of sensors. The collaboration of high interactive energy between interfaces and high fracture toughness of the constituent hydrogels can effectively prevent relatively macroscopic motions of adhesives from substrates under deformation. Nevertheless, variations in surface microenvironment...

Perspectives on recent advancements in energy harvesting, sensing and bio-medical applications of piezoelectric gels

“…149,150 In this context, hydrogels displaying superior bio-functionality and bio-safety characteristics were explored as promising biomaterials for a multitude of applications such as tissue engineering, bio-sensing, wound-dressing, self-recuperating, health-monitoring, regenerative medicine, drug-delivery systems, artificial contact-lens, bio-adhesives, and biomedical microelectromechanical devices. 151–159 Hydrogels, particularly DNA-based materials, have received a lot of attention due to their high biological recognition, good electrical transport, piezoelectricity properties, and intrinsic biocompatibility. 160–164 For example, Ho and coworkers developed a wound infection sensor comprised of DNA hydrogel, which demonstrated excellent biocompatibility, permittivity tunability, capacitive sensing, wireless and battery-free characteristics making them highly suitable for bio-sensing in clinical technology applications (Fig.…”

Dynamic Stimulations with Bioengineered Extracellular Matrix‐Mimicking Hydrogels for Mechano Cell Reprogramming and Therapy

“…While there are hurdles, advances in material design and fabrication (e.g., additive manufacturing) have shown promise in creating in creating the next generation of hydrogels that are more structurally defined and controllable. [28][29][30] A better understanding of the mechanotransduction process will definitely aid in the development of new material design principle (gradient hydrogel).…”

A review of recent advances in metal ion hydrogels: mechanism, properties and their biological applications

“…44 Taking hydrogel adhesives as a starting point, Liu et al reviewed various hydrogel adhesives in the last decade, from design strategy to final application. 45 In addition, the review work by Janarthanan et al focused on the tissue engineering applications of hydrogels composed of metal ions such as Fe 3+ and Zn 2+ . 39 Compared with the above review, this review took metal ion hydrogels as a starting point and summarized the common properties and biological applications of different types of metal ion hydrogels.…”