A nanofluidic emitter tip obtained by focused ion beam nanofabrication

We report here the design, fabrication and testing of a novel nanofluidic device which we term a 'nano-nib' due to its resemblance to a nano-fountain pen. The nanofluidic device is an emitter tip which incorporates a nanofluidic capillary slot coupled to a microfluidic capillary slot. The microfluidic capillary slot is fabricated using reactive ion etching (RIE) whilst the nanofluidic capillary slot is fabricated using focused ion beam (FIB) etching. The microfluidic capillary slot has a length of 2 mm and capillary slot dimensions (w x h) of 1 microm x 4 microm, i.e. a volume of a few picolitres (pl). The smallest nanofluidic capillary slot has a length of 3 microm and capillary slot dimensions as small as 21 nm x 300 nm, i.e. a volume of a few attolitres (al). Current-voltage characterization in electrospray mode revealed a current of 1 nA at an applied voltage as low as 40 V. The applications for this nanofluidic device lie in high sensitivity electrospray mass spectrometry, direct nanowriting, ultralow volume sample extraction/spotting and printing.