Mechanical Characterization of APA Microcapsules by Parallel-Plate Compression

Abstract

We produced microcapsules of alginate-poly(L)lysine-alginate (APA)with diameters on the order of 10 µm. To characterize their mechanical properties, we conducted an experiment on the parallel-plate compression of a microcapsule and modeled its deformation. In the modeling task, the microcapsule was assumed to be a spherical liquidfilled elastic membrane with negligible bending stiffness and permeability. The membrane thickness was estimated by applying Reissner's linear elastic theory to the experimental force-displacement relationship during loading in the small displacement region. The initial stretch of the membrane was taken into account; it was mainly caused by the osmotic pressure difference across the membrane. The initial stretch of the microcapsule was determined by fitting the calculated and experimental force-displacement relationships during loading at small to medium displacements. At large displacements, the calculated force was smaller than the experimentally measured force because of fluid permeation across the APA membrane. The calculated and experimentally imaged shapes of the deformed microcapsule were compared. The effects of varying the membrane thickness on the force-displacement and transmural pressuredisplacement curves were shown, and the limitations of applying the present deformation model were examined.

Programmable Electrodeposition of Janus Alginate/Poly‐L‐Lysine/Alginate (APA) Microcapsules for High‐Resolution Cell Patterning and Compartmentalization

“…Yamaguchi group reported that Young's modulus of the APA membrane could be tuned by changing the thickness of APA membrane coating. [51] Sun et al reported that the APA membrane thickness increases with the increase of the concentration of sodium alginate, calcium solution, and PLL, the reaction time with PLL, and the molecular weight of PLL. [52] On the other hand, grafting functional ligands onto APA microcapsules can be employed to manipulate MSC differentiation.…”