A polysilicon nanoelectrospray-mass spectrometry source based on a microfluidic capillary slot

A novel micromachining process for the fabrication of miniaturised polysilicon-based nanoelectrospray ionisation-mass spectrometry (nanoESI-MS) sources is developed in this paper. The nanoESI source topology is composed of two highly planar triangular free-standing cantilevers which form a microfluidic capillary slot having a width (omega) and a height (h). A combination of low pressure chemical vapour deposition (LPCVD), pattern-transfer, reactive ion etching (RIE) and sacrificial layer etching is used to fabricate the nanoESI sources which project horizontally beyond the edge of a silicon substrate by a length of 800 mu m. NanoESI sources having two different capillary slot dimensions are tested: w x h = 1.8 mu m x 2 mu m and 2.5 mu m x 5 mu m. The sources have been tested on an ion trap mass spectrometer (MS) using a standard peptide sample (Glu-Fibrinopeptide B) at a concentration of 1 mu M. The resultant mass spectra show that the microfabricated capillary slot-based nanoESI sources presented here demonstrate state-of-the-art performances in terms of electrospray ionisation voltage (0.7 kV) and test solution aqueous concentration (90% H,O). (c) 2004 Elsevier B.V. All rights reserved.