Sensorless Viscosity Measurement in a Magnetically-Levitated Rotary Blood Pump

Area of Science:

• Biomedical Engineering
• Fluid Dynamics
• Medical Devices

Background:

• Accurate flow rate control in implantable rotary blood pumps is crucial for matching physiological demand.
• Existing methods for flow rate estimation often require flow meters or lack precise blood viscosity measurements.
• Noninvasive, sensorless methods for blood viscosity are needed for advanced pump control.

Purpose of the Study:

• To develop and validate a sensorless method for measuring blood viscosity in magnetically levitated rotary blood pumps.
• To enable accurate blood viscosity assessment without additional sensors or mechanical components.
• To explore the potential of this method for improving flow rate estimation in blood pumps.

Main Methods:

• A sensorless viscosity measurement technique was developed for magnetically levitated rotary blood pumps.
• Vibrational excitation was applied to the impeller using magnetic bearings.
• Viscosity was determined by measuring the phase difference between magnetic bearing current and impeller displacement.

Main Results:

• The developed method achieved high correlation (R² > 0.992) with reference viscosity measurements.
• Mean absolute deviation for measured viscosity was 0.12 mPa·s across a range of 1.18 to 5.12 mPa·s.
• The technique demonstrated reliable performance for various working fluids.

Conclusions:

• A novel, sensorless method for measuring blood viscosity in rotary blood pumps has been successfully developed.
• This technique eliminates the need for additional sensors, simplifying pump design and improving reliability.
• The validated method shows significant potential for enhancing the accuracy of flow rate control in implantable blood pumps.