One-step electroplating 3D template with gradient height to enhance micromixing in microfluidic chips

A cost-effective method that used electroplating to fabricate a 3D polydimethylsiloxane (PDMS) passive micromixer was developed in this work. The mixer fabrication process characteristics were as follows: The chip design was transferred to indium tin oxide (ITO) glass via photolithography; the ITO glass was vertically immersed in a nickel electroplating solution; and the ITO glass was raised up by controlling by the syringe pump, while electroplating was in progress. In this method, the height of the mixing structure could increase gradient from 15 to 30 μm. Compared with a flat structure, this structure could increase mixing efficiency by at least 10 %. The mixing efficiency with this 3D microstructure can reach more than 80 %. This 3D microstructure fabrication method can be easily integrated with other PDMS functional structures for future point-of-care diagnostic applications because of the advantages of this technique.