Scientists at Moscow State University described the mechanism of an inertial lift, that is, a lift that acts on particles of arbitrary size in microchannels filled with liquid. This was reported in a press release.
The behavior of particles in channels several microns thick depends on the Reynolds number, which describes the flow of a viscous fluid. A lifting force can act on them, as a result of which they move across the flow and stay at a certain distance from the channel walls. Thus, accurate calculations of the motion of particles in the channel make it possible to select the conditions under which the sorting of particles occurs.
Image: Moscow State University.
Since several forces act on particles at once, their behavior is difficult to describe theoretically, therefore, in past studies, they resorted to simplifications. For example, the researchers neglected the size of the particles, representing them as dots, or considered those that move near the channel wall.
Scientists have developed a model that predicts the behavior of finite-sized particles in the middle of the channel. In doing so, they managed to take into account the interaction of particles with the wall. It turned out that if the density of a microscopic body differs from the density of a liquid, then it will also be affected by the force of gravity and the force of Archimedes, which can shift the position of equilibrium.
For small values of the Reynolds number, spherical particles can fly over the channel wall, being at a certain "height". The latter depends on the size and density of the particles, so it is possible to efficiently sort the particles in narrow rather than wide channels. This can be used to screen out cancer cells from healthy ones in medical research.
