A rheological study of packed red blood cell suspensions with an oscillating ball microrheometer

Rheological properties of concentrated red blood cell suspensions are studied with a magneto acoustic microrheometer in which a ball is suspended in a vertically oriented cylindrical tube. The rheometer uses a conventional falling ball technique to measure steady state viscosity and a vertically oscillating, magnetically driven ball for viscoelastic measurements. The motion of the ball is tracked by ultrasound echo location in which sound waves are transmitted and received by an ultrasound transducer mounted at the base of the tube. The compact size of the rheometer allows rheological studies to be made with microliter quantities of opaque suspensions and permits sudden and accurate changes in temperature. Also, values for the adiabatic compressibility are evaluated from measurements of the speed of sound.