Rheological and Mechanical Assessment of Injectable Hydrogels: A Framework for Structure–Property Analysis

ABSTRACT

Injectable hydrogels have attracted massive research attention thanks to their potential biomedical applications. How to evaluate their properties and performance has become a central issue before those applications can be realized. The present review aims to give a concise and structured assessment framework that integrates essential hydrogel properties and appropriate testing methodology for structure–properties evaluation. The framework is constructed from the perspectives of mechanical and rheological tests and incorporates five assessment dimensions that are usually considered and implemented for biomedical applications including (1) network integrity; (2) self‐healing for injectability; (3) mechanical toughness and damage recoverability; (4) stimuli‐responsiveness for physiological adaptation; and (5) viscoelastic stress relaxation to regulate stem cells. For each property dimension, our discussion will focus on application needs, property requirements, rheological or mechanical assessments, results interpretation, and research limitations. Dynamic crosslinks, which endow hydrogels with structural dynamicity and reversibility, play critical roles in achieving these important properties. How rheological and mechanical characterizations can contribute to revealing the structure–property relationship will be analyzed. Meanwhile, the remaining research limitations and emerging opportunities will also be discussed.