Md Mezbah Uddin

Hydrogels can be Newtonian non-Newtonian fluids. If the hydrogel is represented as a liquid, then a small ball of water of 100 nm is compressed by an additional internal pressure of 14.6 atm compared to water in a glass. Such calculations can be done using the Laplace-Perrin law. Therefore, small balls will be more rigid than large ones.

The mechanical properties of the alginate gel depend on the concentration of the alginate it is based on. Its mechanical properties are also influenced by the method of producing the hydrogel. What hydrogel is mentioned in the article and how the measurement was performed. Can these results be compared with those from the AFM for small beads?

Although the properties of the materials are dependent on the atomic and molecular interactions, but in my opinion the overall geometry and the dimensions also play a crucial role in determining the ultimate properties in terms of strength etc.

Md Mezbah Uddin

Hi, If we do not consider the droplet to be ideal, droplets with larger volumes will show more volume changes than pressure droplets with smaller volumes. Due to the definition of the bulk modulus in relatively close volumes, this difference in variation can be ignored. But compared to two drops with large volume differences, it can be said that smaller particles show less volume change with pressure changes, so it can be said that smaller particles are harder than larger particles.

Obviously, if the ideal particle is not considered, it is actually closer to reality.

Mirosław Grzesik Thanks for your help. In the paper, they have fabricated hydrogel beads (50 um) and disks (10 mm dia, 2mm thick) of two different concentration (1.0 and 2.0 wt%). In the report it is mentioned that AFM measurements (on beads) are lower than those done by bulk compressive measurement (on disks).

Now it's clearer. Same hydrogel and different geometry. In the case of hydrogel beads, the cross-sectional area varies (increases and then decreases), and in case of disk is constant. So bead is easier to deform by pressing than a disk. If the effect is linear, then the modulus for hydrogel beads must be smaller.