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Aspects of Applicability King - St. Clair Approximation in a Non-Newtonian Fluid Mechanics

100%

Włoch A. , Czyż H. , Jasiński T.

Acta Physica Polonica A

2017

tom 132

nr 1

164-166

This studyis a contribution to research on the biomedical and clinical applications of ultrasound. Our research concerns the procedure for the separation of human blood fractions - erythrocytes. Ultrasonic waves can be used for the separation of cells in human blood. From a physical point of view, the human blood is a suspension of liquids and solids (cell elements), and behaves like a non-Newtonian fluid. Our work is devoted to the problem of the motion of red cells in human blood under the influence of ultrasonic wave. It defines a range of the applicability of approximation consisting in neglecting the nonlinear term in the friction force. It also analyzes the general properties of the equation of motion of the cell in the case of large attenuation constants, corresponding to the values of the drift forces for the cells with radii of a few μm. Finally, it defines the applicability criterion of the so-called King-St Clair approximation consisting in the assumption of equilibrium between the drift and the Stokes viscosity forces, neglecting the term representing inertia. This approximation permits analytical estimation of the time constants for the cell transport to points of stable equilibrium in an ultrasonic standing wave field.

Development of a drug delivery system using microcapsules with ultrasound

75%

Masuda K.

tom Vol. 31, no. 2

23-32

Micrometer-sized microcapsules collapse upon exposure to ultrasound. Use of this pheno-menon for a drug delivery system (DOS), not only for local delivery of medication but also for gene therapy, should be possible. However, enhancing of efficiency of medication is limited because the capsules in suspension diffuse in the human body after injection, since the motion of the capsules in blood flow cannot be controlled. To control behavior of the microcapsules, an acoustic radiation force was introduced. We detected local changes in the microcapsule density by producing of acoustic radiation force in an artificial blood vessel. Furthermore, we theoretically estimated the conditions required for an active path selection of the capsules at a bifurcation point in the artificial blood vessel. We observed the difference in the capsule density at both in the bifurcation point and in alternative paths downstream of the bifurcation point for the different acoustic radiation forces. We also confirmed that the microcapsules are trapped against flow with the condition when the acoustic radiation force is more than the fluid resistance of the capsules. The possibility of controlling of the capsule flow towards a specific point in a blood vessel was demonstrated.