Microfluid-Assisted Dielectrophoretic Alignment and Device Characterization of Single ZnO Wires

Individual ZnO wires were deposited on two closely spaced electrodes in a microfluidic channel by using the positive dielectrophoretic (p-DEP) alignment technique. By using the p-DEP technique in the presence of a microfluidic force, efficient and rapid alignment of single wires was achieved; this was a result of spatial confinement, uniform wire orientation in the channel, and the competition between microfluidic and DEP forces. The technique helped achieve a capturing efficiency of up to 86% within a few tens of seconds. In addition, we fabricated an electrochemically gated field-effect transistor (EC-FET) using single ZnO wires. The conductivity of the as-aligned wire was enhanced by carrying out post-treatments such as the deposition of metal layers at both ends of the wire, annealing, and functionalization with dodecanedioic acid. By applying a voltage across the electrolyte, it was confirmed that the fabricated EC-FET had stable n-channel FET characteristics.