Cantilever-based bio-chemical sensor integrated in a microliquid handling system

The cantilevers have integrated piezoresistive readout which, compared to optical readout, enables simple measurements on even non-transparent liquids, such as blood. First, we introduce a simple theory for using piezoresistive cantilevers as surface stress sensors. Then, the sensor fabrication based on conventional microfabrication is described and the sensor characterization is discussed. During the characterization we found a stress sensitivity of (/spl Delta/R/R)=4.6:10/sup -4/ (N/m)/sup -1/ and a minimum detectable surface stress change of 2.6 mN/m. Aqua regia etch of gold on top of the cantilevers has been monitored, and immobilization of single-stranded thiol modified DNA-oligos has been detected by the sensor. Finally, it is demonstrated that it is possible to analyze two samples simultaneously by utilizing the laminar flow in the microliquid handling system.