Existing fICP preconcentrators have used thin film electrodes to facilitate electrochemical reactions that generate an IDZ. However, in a tall microchannel or under rapid fluid flow, the IDZ does not extend the full height of the microchannel from the planar electrode, and therefore, a fraction of the analyte escapes, carried over the IDZ by convection (Scheme 1d). This phenomenon decreases the efficiency of enrichment. In prior reports, this challenge has been addressed by decreasing the microchannel height and increasing the applied electric field to augment the IDZ size. However, these approaches sacrifice volumetric throughput and are limited by gas bubble formation, respectively. In a device employed for desalination by ICP, MacDonald and coworkers achieved throughput of up to 20 𝜇L min -1 by using an out-of-plane device, in which a vertical nanoporous membrane was integrated into the wall of a microchannel, thereby increasing the exposed area available for ion transport. Based on this result, we anticipated that a 3D electrode (Scheme 1e) could enhance analyte retention in fICP.