Hollow gel capsules elongated and then buckled after a delay in peer-reviewed laboratory experiments. Researchers linked that sequence to water leaving the capsule and compressing its polymer network. Wall thickness and pipette size affected the response. The capsules recovered when suction stopped; the main experiments used chemically crosslinked artificial gels.
Hollow gel capsules first elongated under suction and then buckled after a delay in one peer-reviewed experimental study. Researchers associated the collapse with water escaping from the capsule and compressing its polymer network. Capsules with thinner walls deformed more readily, and the ratio between wall thickness and pipette radius affected the response. Releasing suction allowed the capsules to recover their starting shapes.[1]
Polyacrylamide, a polymer used to make the artificial gels, was prepared with different densities of chemical crosslinks. A very fine pipette applied controlled suction while microscopy tracked the deformation. Solid particles supplied measurements of elasticity. Tracer particles moving inside the pipette made water flow visible and supported a separate estimate of permeability.[1]
Networks with more crosslinks generally resisted deformation more strongly and allowed less fluid through. Differences in network structure affected the detailed relationship between these properties.[1]
Aggregates of cells grown in the laboratory provided another test of fluid permeability. Fluid flow was more restricted in aggregates that had formed over a longer period. The main gel experiments used permanent chemical crosslinks. Biological gels held together by temporary interactions can relax over time, so the researchers identified observation duration and network relaxation as relevant conditions for applying the method to those systems.[1]
