Pier Luca attended the 86th Annual Meeting of the Society of Rheology in Philadelphia (Pennsylvania, USA) giving the talk:”Viscoelastic focusing down to the nanoscale”.
ABSTRACT – We show that nanoparticles suspended in dilute polymer solution in Poiseuille flow can be trapped in the central region of a microtube. The trap force is due to the viscoelasticity of the suspending fluid, and can be modulated by selecting liquids with specific rheology. We propose a simple theoretical argument that supports the experimental evidence, and links the trapping force to a dimensionless parameter that compares normal forces and Brownian forces. Theese arguments distill into a simple equation, which could be used to downscale flow cytometers, or to design microfluidic devices for counting, coding or separating nanoparticles.