A silicon microneedle array atmospheric pressure plasma ionization source for real-time trace gas chemical analysis

Abstract We have engineered, fabricated, and qualified ZAPPI ( Z onal A tmospheric P ressure P lasma I onizer), an array of hollow electrical discharge emitter micro needles for volatile organic compound ionization and detection. The device is optimized for portable applications requiring low power and trace analyte abundance. The 250 µm interelectrode gap requires just 1.1 mW, detecting analytes at $$\dot{m}=23{ng}{s}^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mover> <mml:mrow> <mml:mi>m</mml:mi> </mml:mrow> <mml:mo>̇</mml:mo> </mml:mover> <mml:mo>=</mml:mo> <mml:mn>23</mml:mn> <mml:mi>ng</mml:mi> <mml:msup> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> mass flow rates. We further demonstrate ZAPPI’s efficacy by ionizing several compounds representing different point of detection applications. These compounds include DMMP a simulated chemical warfare nerve agent, 2-butanone a widely studied biomarker in exhaled breath, Methyl salicylate a flavoring agent, and Naphthalene a toxic polycyclic aromatic hydrocarbon by-product in combustion. The wafer level fabrication of the ZAPPI device opens future possibilities for highly integrated trace gas detection lab on chip systems.