The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.

Microfabrication of Heated Nebulizer Chips for Mass Spectrometry

Ville Saarela

Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Electronics, Communications and Automation for public examination and debate in Large Seminar Hall of Micronova at the Aalto University School of Science and Technology (Espoo, Finland) on the 15th of October 2010 at 12 noon.

Overview in PDF format (ISBN 978-952-60-3340-2)   [12779 KB]
Dissertation is also available in print (ISBN 978-952-60-3339-6)


Microfabrication technologies originating from the semiconductor industry were applied to the instrumentation of analytical chemistry. Heated nebulizer (HN) chips made of silicon and glass were developed. The HN chips are used to vaporize a sample prior to detection by a mass spectrometer. The chips can be used with both liquid and gaseous samples and they are compatible with multiple atmospheric pressure ionization techniques, which enables wide applicability with different separation methods and various types of analytes. Better sensitivity, flexibility and operation with a lower sample and nebulizer gas flow rates was achieved by the miniaturization of the heated nebulizer. The chips can operate with 50 nL min−1 to 5 µL min−1 sample flow rates typical of microfluidic separation systems.

Silicon and glass microfabrication methods – etching, wafer bonding and thin film technology – were developed and applied to the fabrication of the HN chips in 40 different layout and process variations. The thermal behaviour of the chips and the shape of the gaseous jet produced by the chips was studied. A method was developed for measuring the temperature distribution of a gaseous jet using a miniature thermocouple attached to a computer controlled xyz stage.

Different methods for making capillary tube and electrical interconnections to the chips were also studied.

Liquid chromatography (LC) column chips were developed resulting in an integrated chip having both an LC column and a heated nebulizer on a single chip. At the end of the LC column there is a high aspect ratio micropillar frit which enables packing the column with particles.

The novel chips developed in this work extend the available ionization methods and the range of suitable analytes compared to the previously presented chips for mass spectrometry.

This thesis consists of an overview and of the following 6 publications:

  1. Ville Saarela, Sami Franssila, Santeri Tuomikoski, Seppo Marttila, Pekka Östman, Tiina Sikanen, Tapio Kotiaho, and Risto Kostiainen. 2006. Re-usable multi-inlet PDMS fluidic connector. Sensors and Actuators B: Chemical, volume 114, number 1, pages 552-557. doi:10.1016/j.snb.2005.06.009.
  2. Ville Saarela, Markus Haapala, Risto Kostiainen, Tapio Kotiaho, and Sami Franssila. 2007. Glass microfabricated nebulizer chip for mass spectrometry. Lab on a Chip, volume 7, number 5, pages 644-646. doi:10.1039/b700101k.
  3. Kai Kolari, Ville Saarela, and Sami Franssila. 2008. Deep plasma etching of glass for fluidic devices with different mask materials. Journal of Micromechanics and Microengineering, volume 18, number 6, 064010, 6 pages. doi:10.1088/0960-1317/18/6/064010.
  4. Ville Saarela, Markus Haapala, Risto Kostiainen, Tapio Kotiaho, and Sami Franssila. 2009. Microfluidic heated gas jet shape analysis by temperature scanning. Journal of Micromechanics and Microengineering, volume 19, number 5, 055001, 10 pages. doi:10.1088/0960-1317/19/5/055001.
  5. Ville Saarela, Markus Haapala, Jaroslav Pól, Nisse Kalkkinen, Marko Hukka, Kai Kolari, Raimo A. Ketola, Risto Kostiainen, Tapio Kotiaho, and Sami Franssila. 2007. On-chip liquid chromatography - atmospheric pressure ionization - mass spectrometry. In: Proceedings of the 11th International Conference on Miniaturized Systems for Chemistry and Life Sciences (µTAS 2007). Paris, France. 7-11 October 2007. Volume 2, pages 1435-1437. ISBN 978-0-9798064-0-7.
  6. Markus Haapala, Ville Saarela, Jaroslav Pól, Kai Kolari, Tapio Kotiaho, Sami Franssila, and Risto Kostiainen. 2010. Integrated liquid chromatography–heated nebulizer microchip for mass spectrometry. Analytica Chimica Acta, volume 662, number 2, pages 163-169. doi:10.1016/j.aca.2010.01.005.

Keywords: chip, heater, liquid chromatography, mass spectrometry, microfabrication, nebulizer

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Last update 2011-05-26