Discrete element simulation of mechanics properties of single edge notched hydrogel-a new material for soft robot and sensor *

Hydrogels have been widely studied in the field of soft robots in recent years due to their good biocompatibility, controllable electrical properties and mechanical properties, and hydrogels are expected to be promising materials for manufacturing soft robots and sensors. Here, we focus on the simulation of the mechanical properties of hydrogels. A novel simulation model based on discrete element method (DEM) is presented to simulate the fracture properties of notched hydrogels. The method used particle model and wall model to simulate the hydrogel and the force applied to it. Elastic module, viscous module and bonding module were applied between each particle to simulate the real microstructure inside hydrogel. Here, we used regular arrangement particles to simulate the homogeneous hydrogel, and staggered arrangement particles to simulate the inhomogeneous hydrogel. A single edge notched tension specimen, as a typical specimen for testing fracture properties is used to simulate the real broken. The morphology of hydrogels during the single edge notched hydrogel was simulated in detail, and the force-displacement curve, stress-strain curve and strain energy was calculated from the method. The results of the simulation show that the fracture properties were quite different while the arrangement of the particle was changed and the irregular arrangement particles had a better fracture property which was consistent to the real experiment that the fracture property of inhomogeneous hydrogel was better than homogeneous hydrogel. The applicability, simplicity and flexibility of the new approach were demonstrated and the results show that the model has potential in study the movement and the mechanical response for the research of soft materials and robotics.