Hydrogels are colloidal gels composed of polymer networks that are extensively swollen with fluid. Over the past 50 years, they have shown promise in a wide range of applications, including the food industry, sensors, drug delivery, and tissue engineering. Their behavior is influenced by the nonlinear mechanics of polymer networks, poroelastic effects, crosslinking reaction kinetics, thermal mechanisms, and other factors.
Our research focuses on describing the complex mechanical response of hydrogel structures, ranging from rigorous theoretical formulations to robust computational implementations.
Crosslinking effects in swollen hydrogels
Coupling of reaction kinetics, poroelastic effects and nonlinear mechanicsCalcium chloride (CaCl2) is one of the most commonly used cross-linking agents for alginate, as it facilitates simple and rapid gelation through the release of Ca2+ ions. However, cross-linking via CaCl2 is difficult to control due to its high solubility in aqueous solutions. This process changes the topology of the polymeric network, hindering diffusion and influencing swelling behavior. To address these phenomena, a reaction-diffusion model has been developed that accounts for the dependence of diffusion properties on the degree of gelation. Additionally, a chemo-mechanical constitutive model was created to describe how these reaction-diffusion mechanisms interact with shrinking effects, which counteract fluid-induced swelling.
Computational results reveal heterogeneities in the distribution of crosslinks within the hydrogel as a consequence of the standard crosslinking process. The final mechanical and diffusive properties of the hydrogel structures can be quantitatively predicted. Notably, thermodynamic principles demonstrate a two-way coupling between chemistry and mechanics, with the crosslinking reaction rate directly depending on internal mechanical forces.
Optimization of hydrogel response
From experiments through theory to in silico toolsThe fabrication of stiffness gradients in gelatin methacryloyl (GelMA) hydrogels opens up a wide range of technical possibilities, from smart structures to tissue engineering applications. However, precisely controlling the stiffness distribution within the hydrogel is challenging. When a specific target profile is desired, protocols are typically developed through trial-and-error experimentation, making the process expensive and time-consuming. To address this, a digital twin of the GelMA extrusion manufacturing process has been developed, enabling the optimization of process variables to achieve a linear stiffness profile in the extruded construct.
