Fabrication and integration of planar electrodes for contactless conductivity detection on polyester-toner electrophoresis microchips

Authors

  • Wendell Karlos Tomazelli Coltro,

    1. Instituto de Química de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil
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  • José Alberto Fracassi da Silva,

    1. Instituto de Química, Universidade Estadual de Campinas, Campinas, SP, Brazil
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  • Emanuel Carrilho Professor

    Corresponding author
    1. Instituto de Química de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil
    • Instituto de Química de São Carlos, Universidade de São Paulo, Grupo de Bioanalítica, Microfabricação e Separações, Avenida Trabalhador São-carlense 400, P.O. Box 780, 13560-970, São Carlos, SP, Brazil Fax: +55-16-3373-9985
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Abstract

In this report, we describe the microfabrication and integration of planar electrodes for contactless conductivity detection on polyester-toner (PT) electrophoresis microchips using toner masks. Planar electrodes were fabricated by three simple steps: (i) drawing and laser-printing the electrode geometry on polyester films, (ii) sputtering deposition onto substrates, and (iii) removal of toner layer by a lift-off process. The polyester film with anchored electrodes was integrated to PT electrophoresis microchannels by lamination at 120°C in less than 1 min. The electrodes were designed in an antiparallel configuration with 750 μm width and 750 μm gap between them. The best results were recorded with a frequency of 400 kHz and 10 Vpp using a sinusoidal wave. The analytical performance of the proposed microchip was evaluated by electrophoretic separation of potassium, sodium and lithium in 150 µm wide×6 µm deep microchannels. Under an electric field of 250 V/cm the analytes were successfully separated in less than 90 s with efficiencies ranging from 7000 to 13 000 plates. The detection limits (S/N = 3) found for K+, Na+, and Li+ were 3.1, 4.3, and 7.2 μmol/L, respectively. Besides the low-cost and instrumental simplicity, the integrated PT chip eliminates the problem of manual alignment and gluing of the electrodes, permitting more robustness and better reproducibility, therefore, more suitable for mass production of electrophoresis microchips.

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