Measuring the mass density of a target blood cell to calculate its dielectrophoretic force

Dielectrophoresis (DEP) is the motion of a matter caused by polarization effects in a non-uniform electric field. We have been studying to measure dielectrophretic force (DEP force) generated on a small particle by equipment which we developed [1][2][3]. For calculating the DEP force, the mass density of the target particle in the DEP device is necessary. In this paper, we propose to measure the mass density of small particles (µm order) with the “terminal velocity”. And the mass density of polystyrene particle or a target leukocytes which were in the thin space of in the DEP device was measured. In θ=90°, we could not obtain the terminal velocity until 360 sec, because it seemed to fall “irregularly”. In order to solve the problems, how to measure the terminal velocity of a particle was proposed by us. This procedure gave us the mass density of polystyrene particle. This error of estimated value of mass density is up to 4%. The larger the particle size, the smaller the error. The average mass densities of the blood cells, HL60 cell, BALL-1 cell, granular leukocyte and B-cell, were measured to be 1.042g/cm³, 1.043 g/cm³, 1.076 g/cm³and 1.052 g/cm³, respectively.