Xueyu Li

Load-bearing biological tissues, such as muscles, are highly fatigue-resistant, but how the exquisite hierarchical structures of biological tissues contribute to their excellent fatigue resistance is not well understood. In this work, we study antifatigue properties of soft materials with hierarchical structures using polyampholyte hydrogels (PA gels) as a simple model system. PA gels are tough and self-healing, consisting of reversible ionic bonds at the 1-nm scale, a cross-linked polymer netwo

We investigate the fatigue resistance of chemically cross-linked polyampholyte hydrogels with a hierarchical structure due to phase separation and find that the details of the structure, as characterized by SAXS, control the mechanisms of crack propagation. When gels exhibit a strong phase contrast and a low cross-linking level, the stress singularity around the crack tip is gradually eliminated with increasing fatigue cycles and this suppresses crack growth, beneficial for high fatigue resistan

SignificanceDynamic bonds have been found to enhance fracture toughness of hydrogels as sacrificial bonds, but the role of dynamic bonds to fatigue threshold of hydrogels is poorly understood because the wide dynamic range of viscoelastic response imposes a challenge on fatigue experiments. Here, by using polyampholyte hydrogels, we adopted a time-salt superposition principle to access a wide range of time scales that are otherwise difficult to access in fatigue tests. Relations between fatigue

Unlike adult mammalian heart, zebrafish heart has a remarkable capacity to regenerate after injury. Previous study has shown Notch signaling activation in the endocardium is essential for regeneration of the myocardium and this activation is mediated by hemodynamic alteration after injury, however, the molecular mechanism has not been fully explored. In this study we demonstrated that blood flow change could be perceived and transmitted in a primary cilia dependent manner to control the hemodyna

Understanding the dynamic mechanical behaviors of tough hydrogels with ionic dynamic bonds in saline solution is crucial for applications, particularly in the biomedical field. In this work, using polyampholyte hydrogels, dually crosslinked with a primary network from covalent crosslinkers and/or trapped entanglements, and a dynamic network from ionic bonds, as a model system, we investigate the salt effect on rheological response and mechanical behaviors. Through a systematic study on one gel w

Soft materials with mechanical adaptability have substantial potential for various applications in tissue engineering. Gaining a deep understanding of the structural evolution and adaptation dynamics of soft materials subjected to cyclic stretching gives insight into developing mechanically adaptive materials. Here, we investigate the effect of hierarchy structure on the mechanical adaptation of self-healing hydrogels under cyclic stretching training. A polyampholyte hydrogel, composed of hierar

Aiming to establish the relationship between structures of precursor film and its capability of pore formation, high density polyethylene (HDPE) precursor films are prepared under varied draw ratios and die temperatures, which are further subjected to stretching to generate microporous membranes. Structures like long period, lateral size of lamellae, orientation parameter, and fibril content of the precursor films are obtained by small/wide angle X-ray scattering (SAXS/WAXS), and morphologies of