Impedimetric Detection for DNA Hybridization Within Microfluidic Biochips

A fully integrated biochip for the performance of microfluidic-based DNA bioassays is presented. A microlithographically fabricated circumferential interdigitated electrode array of 1- to 5-�m critical line and space dimensions, with associated large area counterelectrode (1000 � WE) and reference electrode (Ag/AgCl), has been developed as a four-electrode system for the electrochemical detection of DNA hybridization using any of the techniques of amperometry, voltammetry, potentiometry, and impedimetry. This is presented as an alternative to optical detection with an emphasis on label-free impedimetric detection of hybridization. A micro total analysis system (�TAS) is presented, using fluidic channels to connect integrated reaction domains with downstream electrochemical detection. This is accomplished by bonding a patterned poly(dimethylsiloxane) (PDMS) substrate to the biochip or by adhesive bonding of the chip to channels fabricated within glass and plastic microfluidic cards, adding increased functionality to the device.