A Universal and Simple Method to Obtain Hydrogels with Combined Extreme Mechanical Properties and Their Application as Tendon Substitutes

With the development of biomedical engineering, the preparation of hydrogels with combined extreme mechanical properties similar to those of some biological hydrogels becomes an important research topic for scientists. In this work, a single-network hydrogel with combined extreme mechanical properties is prepared through a simple and universal method, wherein the strength, elongation at break, toughness, and fracture energy of the hydrogel WPU-3PAAm-6PAN are achieved at 24.7 MPa, 544.0%, 68.9 MJ m-3, and 37.2 kJ m-2, respectively. Herein, a series of photosensitive resins in emulsion form are synthesized, and due to the water-oil diphasic characteristic, hydrophobic monomers and high-efficient hydrophobic photo-initiators are adopted into the resins, which can significantly improve the mechanical properties of the hydrogels due to the hydrophobic association effect and solve the biggest barrier of low curing rate in digital light processing (DLP) fabrication of hydrogels, respectively. Moreover, the simple and facile method to obtain robust and tough hydrogels can be universally applied to other polymer systems. Combined with the excellent mechanical properties and printing ability, the hydrogels with optimized structures are fabricated through DLP printing technology and applied as tendon substitutes. The tendon substitutes exhibit superior performance for mechanical connection and regeneration of collagen fibers. Although further clinical research is required, the hydrogels have great potential applications in various biological areas.