Label-free DNA analysis system based on Lab-On-Glass technology

In this paper we present a lab-on-glass system for label free DNA analysis that integrates a polymerase chain reaction (PCR) chamber for DNA amplification, an electrowetting-based droplet-handling system and a hydrogenated amorphous silicon ultraviolet sensor array for DNA detection. The photosensors allow to measure the absorbance of the biomolecules at 254 nm to reveal and quantify the DNA sample. The system is fabricated using thin-film and thick-film technologies on a conventional microscope glass slide and its design has been carried out by taking into account the application requirements as well as the compatibility of the process steps. The PCR chamber incorporates a thin metal film heater optimized for uniform temperature distribution and an amorphous silicon diode for temperature measurement. The diode shows a sensitivity of -3.3 mV/K in the range 30-80degC when biased with a forward current of 10 nA. A successful droplet handling capability was achieved using a hydrophobic Teflon layer deposited over the silicon nitride film used to passivate both the heater and the ultraviolet sensor array. The voltages needed to successfully move a 2 mul water droplet were in the range of 80 Volts. Finally, we demonstrated the sensor ability to distinguish between single- and double-stranded molecules functionalized on a quartz substrate.