Integrated Optoelectronic Device for On-Chip Detection of Fluorescent Molecules

This work presents the development of a compact optoelectronic device for the on-chip detection of fluorescent molecules. The device structure includes two different components integrated on the same glass substrate: thin film photosensors and a long-pass multi-dielectric filter. The compatibility of the technological processes determines the materials and the temporal sequence of the fabrication. In particular, the photosensor is constituted by a p-type/intrinsic/n-type stacked amorphous silicon layers deposited by plasma enhanced chemical vapor deposition at temperatures ranging from 210 to 300 °C, while the interferential filter, constituted by alternating layers of ZnS and MgF2, has been deposited by electron-beam physical vapor deposition at room temperature. The basic structure proposed for the on-chip detection is qualitatively illustrated in Figure. The system, integrated on a glass substrate, includes: a. the radiation source, to excite the fluorescent dye of the labeled molecules; b. the interferential filter, with a cut-off wavelength between the excitation and emission spectra; c. the a-Si:H photosensors, for the on chip molecules detection. The developed device, coupled with a microfluidic network, has been tested in a system for the detection of ruthenium complex, a molecule frequently used as DNA intercalating dye. Results demonstrate the correct operation of the integrated system both in rejecting the excitation radiation and in detecting the fluorescence signal. In particular, concentrations of double-stranded DNA down to 10ng/L has been successful detected, demonstrating the suitability of this optoelectronic platform in practical biomedical applications.