Viscoelastic Focusing (VEF) is a physical phenomenon discovered at the Technion Israel Institute of Technology. Fluids with specific rheological properties may cause suspended particles to migrate to the center of flow. When such fluids flow through a micro-channel, particles or cells focus at the center and form a single layer plane or a single file depending on the geometry of the micro-channel.
Once the particles are "in focus", they can be optically detected and analyzed.
VEF can be adjusted to different particles and specific particle distributions by an appropriate choice of fluid components.
VEF replaces the traditional hydrodynamic focusing method which is based on sheath flow. It presents a breakthrough in flow cytometry due to its simplicity, its robustness, and its elimination of the need for sheath fluid.