Fabrication and application of stainless steel stamps for the preparation of microfluidic devices

Abstract

The use of an electrochemical polishing process to manufacture stainless steel stamps often gives rise to problems: there is a significant release of gas bubbles that can cause the photoresist mask to peel off. In this paper, a new procedure for the manufacture of stainless steel stamps is presented based on a combination of UV-lithography, gold electroplating, and electropolishing techniques. First, the pattern of the stamp is transferred to a photoresist layer by UV-lithography. The pattern in the photoresist is then filled in with a thin layer of gold formed by electroplating. The photoresist is then removed and the substrate etched in an electropolishing bath, with the gold layer serving as an etching mask. The steel stamps were repeatedly tested for the hot embossing of the polymethylmethacrylate substrate. The imprints were used for the preparation of functional microchips to test their functionality, the chips consisting of two polymethylmethacrylate plates: a plate with microchannels was embossed with a steel stamp, and a plate with inlet/outlet holes. The plates were joined by the thermal bonding method and the microchannels of the chip were then filled with a fluorescein solution to test whether the plates were properly bonded. The results indicate that this new procedure is suitable for the fabrication of flexible and durable masters for a roll-to-roll imprinting process.