Degradation-induced pattern transformation in biodegradable hydrogel porous structures

Biodegradable hydrogels are widely used in biomedical applications due to their degradability, biocompatibility, and ability to transport water and nutrients. Devices such as tissue-engineering scaffolds are often architected into porous structures and operate under constrained physiological conditions. During degradation, hydrolytic chain scission reduces the modulus, leading to additional water uptake even when the gel is initially in equilibrium. This degradation-induced swelling may trigger pattern transformation in porous structures under constraints, altering the local mechanical environment and potentially affecting device performance. To understand this chemo-mechanical behavior, we first revisit and present a simplified version of the previously developed constitutive and computational framework that integrates hydrolytic chain scission, network disconnection, mass loss, and swelling. The constitutive model is then used to investigate degradation-induced pattern transformation in three types of periodic porous structures. We show that the material microstructure and pore structure significantly affect the critical pattern transformation time and reaction stress. These findings provide insights for degradation and programmed structural evolution in biomedical applications, soft robotics, and morphing structures.