Novel reflectivity-difference biosensor

The traditional immobilized biomolecule detection technique on arrays has been fluorescence, but this has limitations because of its reliance on fluorophores. Alternatively, many label-free detection techniques have been developed such as surface plasmon resonance (SPR), ellipsometry, thin-film interference, diffractometry, and waveguides. These techniques have the advantage of high speed and high sensitivity, but in exchange rely on complicated structures or detailed sensing cells. A novel reflectivity-difference biosensor is introduced in this paper. When the sensor covered with a protein layer, the cells and the land would have opposite changes of the reflectance which lead to intensity shifts at the far-field diffraction plane. Therefore, it is convenient for the operation without intricate sensor structures and multifarious optical systems.