Unveiling the poroelastic evolution of agar hydrogels through the drying process

Abstract

Agarose-based hydrogels are widely used in food technology, biotechnology, and biomedical engineering owing to their biocompatibility, tunable microstructure, and well-defined gelation properties. Despite their extensive use, the evolution of their mechanical properties during drying remains insufficiently understood. In this study, we investigate the time-dependent mechanical response of agarose hydrogels subjected to uniaxial compression during controlled ambient drying. Agarose gels of varying concentrations were prepared and characterized using compression testing, dimensional analysis, and microstructural observations. The results reveal a non-monotonic evolution of the Young’s modulus during drying. In the early stages (within the first 24 h), a slight but reproducible decrease in stiffness is observed, which is attributed to mechanical instability of the semi-flexible polymer network induced by shrinkage. At longer drying times (24–72 h), continued water loss leads to pore collapse, network densification, and a pronounced increase in stiffness. These observations indicate the presence of two competing mechanisms governing the mechanical response: network buckling at short drying times and pore buckling at extended drying times. By correlating macroscopic mechanical measurements with microstructural evolution, this work provides a mechanistic framework for understanding the drying-induced mechanical behavior of agarose hydrogels. These findings are relevant for the design and optimization of agarose-based materials in applications where controlled dehydration and mechanical stability are critical.