To clarify the role of the metallic beads, we evaluated a control, in which PSC beads overlaid the Au planar electrode (PSC/Au device). Figure Figure shows current transients obtained for all three device architectures. Full experimental details are included in the SI. Briefly, the microchannel was filled with 40.0 mM Tris buffer and . Then, a flow rate of 10 nL min -1 was established and allowed to equilibrate for 10 min. Finally, the current was monitored following application of V + = 7.0 V (for results at V + = 5.0 V and 10.0 V, see Figure ). The current transient obtained with the planar Au device (blue line, Figure )