Hydrogels are soft, water-rich polymer networks whose mechanical behaviour governs applications ranging from biomedicine to packed bed processes. In aerogel manufacturing, hydrogel particles represent an intermediate state in which the mechanical stability determines scalability and process reliability. Predictive particle-scale models for such deformable matrix-fluid systems have so far remained limited.
Biopolymer-based hydrogel particles were investigated under uniaxial compression in monotonic, cyclic and stress-relaxation experiments at compression rates between 0.1 and 3.0 millimetres per second. The apparent stiffness increased strongly with the rate and saturated above 0.5 millimetres per second, where the apparent Young's modulus became rate independent. Within the elastic regime, which extends to a strain of about 0.5, the response was reproducible and hysteretic, whereas higher strains induced plastic deformation. Ageing over one year led to additional stiffening, indicating an ongoing structural evolution.
To complement the experiments, a novel discrete element framework based on tetrapod-shaped parcels is introduced. The tetrapods qualitatively represent the three-dimensional polymer network and predominantly carry the mechanical loads, while embedded spheres mimic the aqueous phase. The parameters of the model were calibrated using a full-factorial design and Bayesian optimisation.
The simulations reproduce the force-strain response, the apparent elastic properties and the deformation of the particles, and random packings produce a comparable scatter, while stress relaxation and cyclic loading are reproduced qualitatively. Validation on experiments that were not used for the calibration confirmed the load-bearing tetrapod network and the internal redistribution of fluid. The approach advances the predictive modelling of deformable particles and provides a basis for simulations of solvent exchange and of processes at production scale.
The study is a collaboration between the Institute of Thermal Separation Processes at Hamburg University of Technology together with the United Nations University Hub on Engineering to Face Climate Change (UNU-INWEH), the Institute of Process and Particle Engineering at Graz University of Technology and Aerogel-It GmbH, carried out within the Collaborative Research Centre CRC 1615 (SMART Reactors) and the Research Training Group GRK 2462.
Lara Gibowsky, Lukas Maier, Nanning Jaeschke, Irina Smirnova, Stefan Radl, Pavel Gurikov (2026). Hydrogel particles under uniaxial compression: Tetrapod-based DEM approach and experimental validation. Materials & Design 270, 116860.
https://doi.org/10.1016/j.matdes.2026.116860
