HORIBA Medical, Montpellier, france Damien Isèbe Multiphysics Simulation Story: Optimizing Hematology Analysis: When Physical Prototypes Fail, Simulation Provides the Answers HORIBA Medical, Montpellier, france Damien Isèbe

The Challenge Hematology analysis helps medical professionals make diagnosis and treatment decisions Electrical impedance measurements are used to detect blood cell types Hematology equipment setup includes electrodes and a microaperture leading into a counting chamber Counting chamber design Particle orientation and trajectory near the chamber microaperture can cause inaccurate estimates of particle size Top: schematic of impedance measurement using hematology equipment. Bottom: voltage measurements affected by different particle orientations.

The Solution Use hydrodynamic focusing to reduce analysis errors Sheath flow controls the sample travel rate inside the aperture Direct sample flow along the central axis is possible, avoiding edge trajectories Understand phenomena involved and determine best configuration for improving measurement accuracy with multiphysics simulation COMSOL simulation of hydrodynamic focusing, showing how sheath flow (blue surface) directs the sample (red surface) along the central axis of the aperture.

The Simulation Simulate micro aperture-electrode system using COMSOL Multiphysics® Pressure drop Fluid velocity Heat transfer Electric fields Use results to enhance performances of impedance measurement system Account for variation in particle trajectory and orientation Optimize device configuration Simulation confirmed that hydrodynamic focusing greatly improved measurement accuracy Simulation results showing the electric field inside the aperture; T1 and T2 indicate particle trajectories along the central axis and at the edge, respectively.