Poly(dimethylsiloxane) microchip: microchannel with integrated open electrospray tip

TLDR

The study presents a polymer microchip featuring an open electrospray tip for mass spectrometry. The chip comprises a groove with parallel walls forming a droplet at the tip, is covered by a lid except at the tip, and is fabricated by casting PDMS into a nickel mould derived from a dry‑etched silicon wafer. Tips of ~50 µm width were easily replicated, the uncovered tip simplified assembly, and the device achieved a 5 % total ion current variation over 300 s for a 1 µM myoglobin solution, demonstrating the robust mould’s utility for PDMS and rigid thermoset electrospray tip fabrication.

Abstract

A polymer microchip with an open tip for electrospray mass spectrometry is presented. The tip consists of a groove with parallel walls where a droplet can form at the end surface. A lid covers the whole chip except at the microchannel tip, which is left open. Poly(dimethylsiloxane) (PDMS) microchips were cast using a nickel mould which in turn was replicated from a dry etched silicon wafer. Tips with microchannel widths of around 50 µm could easily be replicated. Since the tip had no cover, the assembly of microchip and cover was simplified. A total ion current variation of 5% during 300 s was achieved for a 1 µM myoglobin solution. The non-complex design of the cover makes it suitable for versatile tests of chip prototypes. The nickel mould was found to be useful for PDMS microstructure fabrication. Also, such a robust mould allows casting electrospray tips in more rigid thermoset materials.