Microfluidic networks for patterning biomolecules and performing bioassays

Microfluidic networks (µFNs) are passive, self-filling devices which can be used for depositing lines of biomolecules on surfaces at high resolution. We have explored the use of µFNs replica molded in poly(dimethylsiloxane) (PDMS) or micromachined in Si. The density of biomolecules patterned on a substrate can be controlled through the channel geometry and surface chemistry, and through the volume and concentration of injected biomolecules. For instance, hundreds of micrometer long density gradients of adsorbed biomolecules could be formed. Further, we used µFNs to perform bioassays in an array-format with a spot size of 20 × 20 µm2. We present advanced µFNs and a sealing strategy relying on free surface energy. Hard Si µFNs can thus be sealed onto a hard substrate by simply pressing the two surfaces against each other.