Electromagnetic Micropores: Fabrication and Operation

Abstract

We describe the fabrication and characterization of electromagnetic micropores. These devices consist of a micropore encompassed by a microelectromagnetic trap. Fabrication of the device involves multiple photolithographic steps, combined with deep reactive ion etching and subsequent insulation steps. When immersed in an electrolyte solution, application of a constant potential across the micropore results in an ionic current. Energizing the electromagnetic trap surrounding the micropore produces regions of high magnetic field gradients in the vicinity of the micropore that can direct motion of a ferrofluid onto or off of the micropore. This results in dynamic gating of the ion current through the micropore structure. In this report, we detail fabrication and characterize the electrical and ionic properties of the prepared electromagnetic micropores.

Applications of microelectromagnetic traps

“…The thickness of this layer also provides a method to alter the local magnetic field to direct the motion of magnetic particles. Several reports have shown that the magnetic field and gradient changes as a function of distance (z) above the METs [18,21,28,29]. For a meander MET, for example, the magnetic field generated away from an adjacent pair of wires was partially cancelled by the fields generated by the two wires immediately next to the pair.…”

“…For example, Fig. 3 shows optical micrographs of particles trapped with singlecoil METs of various sizes and insulation thicknesses [29]. Here, a 100 μm OD single-coil MET with a polydimethylsiloxane (PDMS) layer 5 μm thick resulted in particles trapped at the surface of the microwire (Fig.…”

“…Addition of an external magnetic field can generate attractive and repulsive forces that depend on the direction of current flow through the METs. This is extremely useful for manipulation of MPs at multiple locations with a single MET or over long distances with multiple METs [29][30][31][32][33][34][35][36]. Attractive and repulsive forces are created by coupling between magnetic fields of the METs and the external magnet.…”

“…[29]. Copyright (2010) American Chemical Society [29]. Finite element simulations of the magnetic fields showed that two distinct magnetic field distributions were produced, dependent on the direction of the simulated current.…”

“…This showed that two identical DNA molecules tethered between the MPs could be Reversible blockage of ion current Magnetic microvalves have been developed to externally control transport within microfluidic channels [70,71]. A simple method of controlling transport through microscopic structures with METs was developed by Basore et al [29,30]. Single-coil METs with a micropore in the center of the trap were fabricated on silicon and used to reversibly gate ionic transport with a droplet of ferrofluid.…”