Inertio-elastic focusing of particles in microchannels

A system for focusing particles suspended within a moving Newtonian fluid, the system comprising:

• a substrate including a channel having an inlet and an outlet;
• a Newtonian fluid having a dynamic viscosity that varies with shear rate and that carries suspended particles, mixed with a drag-reducing polymer;
• a pump to drive the Newtonian fluid through the channel at a volumetric flow rate that results in the formation of a laminar flow and a localized pathline in the Newtonian fluid at or near a center of the channel, wherein the localized pathline defines a width that is substantially equal to or greater than a hydraulic diameter of the particles;
• and
• a controller configured to control operation of the pump based on dynamic viscosity and volumetric flow rate of the Newtonian fluid, wherein during use the controller is configured to control the pump to drive the Newtonian fluid through the channel at a volumetric flow rate of at least 0.6 ml/minute while maintaining a laminar flow such that the system focuses the particles in the Newtonian fluid into the localized pathline.

A method for focusing particles suspended within a moving viscoelastic Newtonian fluid, the method comprising:

• adding a drag-reducing polymer to the viscoelastic Newtonian fluid;
• providing a substrate including a channel having an inlet and an outlet;
• and
• driving the viscoelastic Newtonian fluid that carries suspended particles through the channel at a volumetric flow rate of at least 0.6 ml/minute that results in the formation of a laminar flow and a localized pathline in the viscoelastic Newtonian fluid at or near a center of the channel, wherein the localized pathline defines a width that is substantially equal to or greater than a hydraulic diameter of the particles,
• wherein the particles in the viscoelastic Newtonian fluid are focused into the localized pathline.