Fundamental investigation for developing drug delivery systems and bioprocess with shock waves and bubbles - (Numerical analysis of deformation of cell model and observation of bubble behaviour near the cell-membrane model)

This paper describes the fundamental investigations for developing new technology using shock waves and bubbles, such as drug delivery systems (DDS) and bioprocess for environmental protection. To understand the fundamental phenomena, the coupling oscillation problems between the deformations of the cell including a bubble and the flow when underwater shock waves propagating are analyzed using computational fluid dynamics (CFD) and optical visualization. For this analysis, the cell is modeled as a liquid droplet including a gas bubble. The effects of (1) the differences of acoustic impedance between internal and surrounding fluid and (2) the boundary motion of the cell on the flow field (density) are discussed using ALE (Arbitrary Lagragian-Eulerian) computational method. The result shows that the effects of the differences of the acoustic impedance and the existence of a bubble in a cell are large for the deformation process of the cell itself. For the optical visualization, deformation process of a bubble near the elastic wall is observed as a. model of cell membrane by shock waves to analyze the behavior of the bubble in the cell or microcapsule. From this result, it is suggested that there should be optimized or critical point to have large deformation of the bubble while changing initial position and initial diameter of the bubble in the cell and relative curvature of the wall (cell diameter), which may be enough to have, large deformation to cracking the cell membrane. From these two results, it is found that if the proper parameters are selected, there are possibilities to make the large deformation enough to crack the cell membrane efficiently comparing with that has no bubbles when the shock waves and bubbles are applied to the fields of DDS or bioprocess.