Department of Chemical & Biomolecular Engineering, University of Melbourne, Parkville, Victoria 3010, Australia.
Soft Matter. 2020 Jun 10;16(22):5314-5324. doi: 10.1039/d0sm00191k.
Hydrogels can be formed in a number of different geometries depending upon desired function. However, due to the lack of appropriate models required to interpret experimental data, it remains unclear whether hydrogel microparticles have the same poroelastic properties as hydrogel films made with the same components. We perform numerical simulations to determine the universal force relaxation of a poroelastic hydrogel particle undergoing constant compression by a spherical probe, allowing analysis of experimental measurements of hydrogel particle material properties for the first time. In addition, we perform experimental measurements, using colloidal probe atomic force microscopy, of the force relaxation of polyacrylamide films and particles made with identical monomer and cross-linker concentrations. We fit our universal curve to the experimental data in order to extract material properties including shear modulus, Poisson's ratio and solvent diffusivity. Good agreement is found for the shear modulus and Poisson's ratio between the particles and the films. In contrast, the diffusivity of the polyacrylamide particles was found to be about half that of the films, suggesting that differences in the synthesis and homogeneity of the films and the particles play a role in determining transport and subsequent release of molecules in hydrogel particles.
水凝胶可以根据所需的功能形成多种不同的几何形状。然而，由于缺乏解释实验数据所需的合适模型，仍然不清楚具有相同成分的水凝胶微球是否具有与水凝胶薄膜相同的多孔弹性性质。我们进行数值模拟以确定多孔弹性水凝胶颗粒在球形探针持续压缩下的普遍力松弛，从而首次允许分析水凝胶颗粒材料性质的实验测量。此外，我们使用胶体探针原子力显微镜进行实验测量，以测量具有相同单体和交联剂浓度的聚丙烯酰胺薄膜和颗粒的力松弛。我们将我们的通用曲线拟合到实验数据中，以提取包括剪切模量、泊松比和溶剂扩散率在内的材料性质。发现颗粒和薄膜之间的剪切模量和泊松比吻合良好。相比之下，聚丙烯酰胺颗粒的扩散率约为薄膜的一半，这表明薄膜和颗粒的合成和均一性差异在决定水凝胶颗粒中分子的传输和随后释放方面发挥了作用。
