Peeling Back the Layers: Solvent-Induced Fracturing in PEG-based Hydrogels

PEG-based hydrogels are widely recognized for their exceptional ability to absorb large amounts of solvent while maintaining their structural integrity. Our previous work identified regimes where solvent imbibement induces stresses large enough to cause large-scale material rupture during the process of swelling. This talk will focus on the reverse process, solvent evaporation, and show that under certain conditino, this too can generate large material stresses which lead to rupture, cracking, and, most notably, peeling. Here, we investigate the drying-induced fracturing and peeling of PEG-based hydrogels, focusing on how varying the network composition (ratio of PEGDA to PEGMEA) and changing the solvent (ethanol, acetone, and water) influences these failure behaviors. Our experiments reveal that peeling is a generic response to drying-induced stresses, but the specific peeling and cracking patterns vary significantly depending on the polymer composition and solvent interaction. We observe that the peeling dynamics closely resemble exfoliation seen in other polymer systems, and the balance between solvent evaporation rate, internal tensile forces, and surface compressive stresses drive the particular morpholgy we observe. Moreover, we find that solvent volatility plays a critical role in determining the rate and extent of fracturing. By quantifying the control parameters for drying-induced fracture, this work provides crucial insights into the mechanics of cracking and peeling, potentially offering strategies to design more durable PEG-based hydrogels.