Sensorless Viscosity Measurement in a Magnetically-Levitated Rotary Blood Pump.
Controlling the flow rate in an implantable rotary blood pump based on the physiological demand made by the body is important. Even though various methods to estimate the flow rate without using a flow meter have been proposed, no adequate method for measuring the blood viscosity, which is necessary for an accurate estimate of the flow rate, without using additional sensors or mechanisms in a noninvasive way, has yet been realized. We have developed a sensorless method for measuring viscosity in magnetically levitated rotary blood pumps, which requires no additional sensors or mechanisms. By applying vibrational excitation to the impeller using a magnetic bearing, we measured the viscosity of the working fluid by measuring the phase difference between the current in the magnetic bearing and the displacement of the impeller. The measured viscosity showed a high correlation (R(2)  > 0.992) with respect to a reference viscosity. The mean absolute deviation of the measured viscosity was 0.12 mPa·s for several working fluids with viscosities ranging from 1.18 to 5.12 mPa·s. The proposed sensorless measurement method has the possibility of being utilized for estimating flow rate.
Precision and Intelligence Laboratory, Tokyo Institute of Technology, Yokohama, Japan.
Wataru
W
Hijikata
Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama, Japan.
Jun
J
Rao
Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama, Japan.
Shodai
S
Abe
Division of Research and Development, MedTech Heart Inc., Tokyo, Japan.|Department of Cardiovascular Surgery, Nihon University School of Medicine, Tokyo, Japan.
Setsuo
S
Takatani
Precision and Intelligence Laboratory, Tokyo Institute of Technology, Yokohama, Japan.
Tadahiko
T
Shinshi
D001783:Blood Flow Velocity; D001809:Blood Viscosity; D004867:Equipment Design; D006353:Heart-Assist Devices; D006801:Humans; D008280:Magnetics / Q000295:instrumentation*; D011673:Pulsatile Flow
Flow rate estimation; Magnetically levitated rotary blood pump; Phase difference; Sensorless viscosity measurement; Vibrational excitation