A Microfabricated Nebulizer for Liquid Vaporization in Chemical Analysis

• Published in: Journal of microelectromechanical systems Vol. 15; no. 5; pp. 1251 - 1259
• Main Authors: Franssila, S., Marttila, S., Kolari, K., Ostman, P., Kotiaho, T., Kostiainen, R., Lehtiniemi, R., Fager, C.-M., Manninen, J.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.10.2006; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Analytical chemistry; Anisotropic magnetoresistance; Applied sciences; Channels; Chemical analysis; Chip formation; Chips; Corona; Etching; Exact sciences and technology; Fluidics; Glass; Infrared heating; infrared imaging; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Liquids; Mass spectrometry; Mass spectroscopy; Mechanical engineering. Machine design; Mechanical instruments, equipment and techniques; micromachining; Micromechanical devices and systems; Needles; Physics; Platinum; Precision engineering, watch making; Silicon; Vaporization; Infrared thermography; micromachining; Chemical analysis; Anisotropic etching; Heating element; Chemical etching; Experimental study; Heat resistant glass; Vaporization; Liquid; Reactive ion etching; infrared imaging; Platinum; Needle; Silicon; Mass spectrometer; Nebulizer; Mass spectrometry; Microelectromechanical device; Fluidics
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2006.879671

A miniaturized nebulizer chip for vaporization of liquid samples for mass spectrometry has been designed, fabricated, and characterized for fluidic and thermal performance. Silicon/glass chip has a liquid sample channel placed centrally between symmetric nebulizer gas channels. The liquid sample is nebulized and vaporised by an integrated platinum heater. The vaporized sample exits through an etched nozzle, and is ionized by an external corona needle. The ions are analysed by a mass spectrometer. The chip has been fabricated in both anisotropically wet etched and DRIE versions in silicon, with an anodically bonded Pyrex glass cover plate. Three different fluidic inlet designs are presented, with both through-wafer and edge insert versions. The shape of the erupting gas jet has been visualized by infrared thermography by using a low-diffusivity imaging screen and high heat capacity helium as a test gas. Dimensions of the jet's thermal footprint on the screen show that the jet is very narrow and confined, and this is confirmed in mass spectrometry results. This confined jet supplies the sample to the ionization region near corona tip, enabling efficient use of very small sample amounts and submicroliter flows.1591