Microcantilever-based biosensors are a promising tool to detect biomolecular interactions in a direct way with high accuracy. We show the development of a portable biosensor microsystem able to detect nucleic acid hybridization with high sensitivity. The microsystem comprises an array of 20 micromechanical cantilevers produced in silicon technology, a polymer microfluidic system for delivery of the samples, an array of 20 vertical cavity surface emitting lasers (VCSELs) with collimated beams thanks to an integrated microlens array, an optical coupling element to provide the optical path required, and chips with the photodetectors and the CMOS circuitry for signal acquisition and conditioning, capable of measuring the cantilever deflection with sub-nanometer resolution. Robust immobilization and regeneration procedures have been implemented for the oligonucleotide receptor sequences. In a further innovation, an optical waveguide cantilever transducer has been also developed in order to improve the final performance of the device. This has a number of advantages in terms of a simple optical geometry and improved sensitivity.

Under the Optonanogen project (EU contract IST-2001-37239), a novel biosensor has been developed, which incorporates a disposable acrylic polymethylmethacrylate (PMMA) fluidic header. This header is designed to deliver a sample to a series of chemically primed cantilevers where hybridization of target DNA sequences and resulting deflection of the cantilevers is detected optically. Two different microfluidic headers are described, which are designed to incorporate the cantilever chip and which demonstrate a novel approach to microfluidic header assembly, integration with macroscale fluidics, fluidic handling, and priming strategies. The first header facilitates the delivery of a single fluid sample to all cantilevers, whereas the second permits discrete delivery of samples to isolated cantilevers, despite all cantilevers being contained on a single chip. This second, multi-path header therefore allows simultaneous analysis of multiple samples, or multiple parallel tests on a single sample. This paper describes these headers and for the multi-path device details the design changes incorporated to ensure effective isolation of the sample including a novel valve to improve priming of the microfluidic circuit.