Figure 1.

Silicon chip with an array of electrodes. (A) Overview of the microfabricated device. Chip dimension was 1 cm square. Light squares along the perimeter are exposed platinum contact electrodes for connections to power supply. Light lines are platinum leads insulated with dielectric, connecting contact electrodes to the exposed platinum electrodes. (B) Electrode array region of the chip. The central 1 × 1 mm test site array region consists of 4 large (160-μm diameter) corner electrodes and 25 central 80-μm electrodes. Pt, exposed Pt test sites; Si₃N₄, dielectric; Si₃N₄ over Pt, Pt insulated by Si₃N₄. (C) Cross section of an electrode test site. Location of section is indicated by lines extending from B. Pt, Si₃N₄, Pt insulated by Si₃N₄; SiO₂, dielectric layer; Si substrate, wafer material; Permeation Layer, agarose layer containing streptavidin; DNA, biotinylated oligonucleotides bound to streptavidin. DNA binding was not limited to the surface.