Figure 6

Detection of colloidal particle immobilization at the aperture (2 µm) by monitoring the streaming current. (a) Schematic illustration of the main steps for the immobilization process of colloids (α−δ). Blue arrows depict fluid flow and white arrows depict the externally applied pressure in the channel. (b) Corresponding optical microscopy images for main steps. The orange circles depict the position of the 4 µm latex bead, while the black arrows depict its movement. (c) Streaming current during manipulation. The difference for an ‘open’ and ‘blocked’ aperture, respectively, at an applied pressure of –500 mbar is indicated. (d,e) Streaming current from independent aspiration experiments for the ‘open’ and ‘blocked’ state in function of aspiration pressure for 0.1 mM and 1 mM ionic strengths, respectively. Dashed lines are only guides to the eye.