Electroanalytical cells pencil drawn on PVC supports and their use for the detection in flexible microfluidic devices

A simple, effective and low-cost technique is here presented for assembling flexible and robust electrochemical devices on transparent PVC supports, using ordinary tools, all installed on a commercial desktop digitally controlled plotter/cutter. Small diamond burs were first set up to rough precise and well defined patterns on the surface of smooth and flexible PVC transparent films. Subsequently, reference, counter and working carbon electrodes were drawn onto abraded patterns by using micropencils (4B graphite leads, 0.5 mm in diameter), in their turn installed on the plotter/cutter. The effective active working surface of electrochemical cells was then defined by a thin adhesive strip or by covering the patterned support with a suitably cut adhesive layer, depending upon whether they were intended for use in batch or drop mode. After optimization of fabrication parameters, such as pressure and speed adopted during bur abrasion and pencil drawing, the electrochemical characterization of these cells was performed by using potassium hexacyanoferrate(II) as redox probe. Voltammetric responses displayed a good inter-device reproducibility (5.6%), thus confirming the effectiveness of this easy and fast assembling strategy. These PVC-based pencil-drawn electrochemical cells were then integrated as thin-layer detectors in adhesive-tape based microfluidic channels, cut and prepared in their turn using the digitally controlled plotter/cutter. These detectors offer the advantage given by the impermeability of PVC supports, thus avoiding absorption of the flowing carrier and consequent analyte broadening, instead occurring when electrochemical cells are pencil drawn on hydrophilic materials as paper. After optimization of the complete fabrication process, the effectiveness of these devices was tested by a proof-of-concept direct quantification of ascorbic acid in commonly used drugs.