Fabrication and fluidic characterization of silicon micropillar array electrospray ionization chip

Lauri Sainiemi*, Teemu Nissilä, Ville Jokinen, Tiina Sikanen, Tapio Kotiaho, Risto Kostiainen, Raimo A. Ketola, Sami Franssila

*Corresponding author for this work

    Research output: Contribution to journalArticleScientificpeer-review

    42 Citations (Scopus)


    A silicon electrospray ionization (ESI) chip for the mass spectrometric analysis is designed, fabricated, and characterized. The chip has three parts: a liquid sample introduction spot, a flow channel, and a sharp electrospray ionization tip. A regular micropillar array is micromachined inside the whole channel. The chip has no lid, which makes the sample application and chip fabrication easier. A two photomask level fabrication process utilizes nested masks of silicon dioxide and aluminum oxide. A combination of anisotropic and isotropic plasma etching steps allows formation of a truly three-dimensional electrospray ionization tip without double-sided lithography. The filling properties of the lidless micropillar channel are studied. Because of the capillary forces facilitated by the micropillar array, the sample applied onto the sample introduction spot spontaneously fills the whole flow channel including the electrospray ionization tip, without external pumping. Besides reliable self-filling, the chip offers stable electrospraying and high sensitivity chemical analysis when coupled to a mass spectrometer (MS).

    Original languageEnglish
    Pages (from-to)380-387
    Number of pages8
    JournalSensors and Actuators B: Chemical
    Issue number2
    Publication statusPublished - 16 Jun 2008
    MoE publication typeA1 Journal article-refereed


    • Capillary filling
    • Electrospray ionization
    • Mass spectrometry
    • Microfluidics
    • Micropillars
    • Silicon microfabrication


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