Electrodeposition combined with microjet flow: fabrication of metal microtubes

A concept of using electrodeposition and microfluidic flow for the fabrication of metal microtubes on a silicon wafer is presented. Microsized holes (2-100 mum) were first etched on a wafer. After depositing a Ti/Cu seed layer on the wafer, electrodeposition of copper was realized. By the use of a water flow through the holes during deposition, clogging of the holes was prevented. Thus, the holes were copied into the resulting copper layer. A second electrodeposition was then performed using a flow of gold electrolyte through the holes. Gold was thereby deposited on the inner walls of the hole structures. Subsequent selective etching removed the copper layer, leaving free-standing, out-of-plane gold tubes on the wafer surface. This method could be useful in fabricating devices for cell handling and lab-on-a-chip