High-resolution liquid volume detection in sub-nanoliter reactors

Miniaturized reactors with volumes of 60 and 540 pi with integrated contact-less liquid volume detectors are fabricated on silicon. Aluminum electrodes are fabricated in the bottom of the reactors and covered with silicon nitride for electrical insulation. The reactors are formed in a 6-mu m thick SiO2 layer by dry etching. The liquid volumes in the reactors are determined by using an impedance measurement and compared to the optical fluorescence microscopy measurements for reference. The applicability of the measurement device for different liquid compositions and reactor size is studied. The presented contact-less measuring method can be used to measure sub-nanoliter liquid volumes with a resolution better than 1 pi. The integrated volume measurement method can be employed in miniaturized automated arrays in High Speed Screening (HSS) systems to determine the dispensed liquid volume. (C) 2000 Elsevier Science S.A. All rights reserved.