Fig. 3: Manipulating particle velocity as a function of applied voltage.

a Theoretical and experimental comparisons of the fully developed velocity profile of the microparticles inside the microtube (radial position) due to fluid flow. Note that the spheres on the tube walls (at ±12.5 µm) still have a nonzero velocity as they tend to roll on the inner-wall. b Change in the velocity profile (net increase in particle velocity) due to the external electrostatic force (F_E). c Particle velocity as a function of applied bias. The blue arrow depicts the increasing magnitude of the applied bias and the orange arrow depicts the direction of the electric field inside the microtube. As the voltage is gradually increased, the velocity profile flattens d as evident from the downward trend (hollow black arrow) in the standard deviation of the particle velocity with respect to increasing bias. Moving further away from the center the difference is more noticeable due to edge effects