Ji Liu

The fatigue failure of soft materials is a problem that has plagued the development of materials, mechanics, and devices in multiple disciplines, and has not been solved for many years. The anti-fatigue properties of traditional tough hydrogels are very poor, and fatigue fracture is likely to occur under multiple cycles of loading, and its fatigue threshold is only 10-100 J/m². Fatigue fracture is one of the main factors affecting the lifespan of hydrogel-based biomaterials. Therefore, how to design anti-fatigue hydrogels is one of the major challenges in the field of soft materials.

Inspired by the relationship between the structure and performance of biological tissues, Dr. Ji Liu, an associate professor in the Department of Mechanical and Energy Engineering of Southern University of Science and Technology, proposed a general strategy to engineer the fatigue-resistant properties of soft materials by synergizing principles in mechanics, chemistry, biomimetics, and bioengineering.

In 2019, while Ji was still a postdoctoral fellow in the laboratory of Professor Xuanhe Zhao of the Department of Mechanical Engineering at MIT, he published a paper in Science Advances as a co-first author under the title Anti-fatigue-fracture hydrogels. Ji brought up the general design rationale for fatigue-resistant hydrogel: fracture beyond the amorphous chains. By engineering the hydrogels with either nanocrystalline domains or nanofibril structures, Ji developed functional hydrogels exhibiting a record-high fatigue threshold over 1,000 J/m2, outperforming all of those synthetic hydrogels.

Ji's research has been focusing on imitating the construction strategy of biological tissues, designing, and manufacturing biological materials comparable to the mechanical properties of biological tissues, and promoting them to the field of human technology, such as wearable devices or implantable electronics, and brain-computer interface, etc.

In Ji's vision, 3D printing and manufacturing of hydrogel materials will be developed in the future. He hopes to combine the existing soft material design and manufacturing technology with new sensor technology and additive manufacturing technology to realize fully functional devices made by hydrogel materials.