Miniaturized multichannel electrospray ionization emitters on poly(dimethylsiloxane) microfluidic devices

A multichannel electrospray ionization (ESI) emitter was fabricated as part of a poly(dimethylsiloxane) (PDMS) microfluidic device using a three‐layer photoresist process which also produces a self‐alignment system to make a bonding between the top and bottom PDMS parts. The prototype device (2 cm high×5 cm wide×5 cm long) had 16‐channels (30 νm wide×50 νm deep) with emitters of 1 mm length and 60° point angle. The PDMS emitter tips enabled interfacing the device to ESI‐mass spectrometry; a stable electrospray from the tips was performed with limits of detection under 1 νM for reference peptides (adrenocorticotropic hormone fragment 1–17, angiotensin I and III).