High-speed label-free detection by spinning-disk micro-interferometry.

Spinning-disk interferometers are a new class of analytic sensors to detect immobilized biomolecules with high speed and high sensitivity. The disks are composed of a large number of surface-normal self-referencing interferometers, analogous to an optical CD, but operating on the principle of microdiffraction quadrature that achieves sensitive linear detection of bound molecules. The surface-normal structures have a small footprint of only 20 microm each, allowing potential integration to over a million interferometric elements per disk. We have fabricated interferometric microstructures on silicon and on dielectric mirror disks to demonstrate the basic principles of the BioCD. We have detected the presence of immobilized anti-mouse IgG and the specific binding of 10 femtomol of mouse IgG at a sampling rate of 100 kilo-samples/s, while also demonstrating negligible non-specific binding. This technique provides a label-free method that could potentially screen hundreds to thousands of proteins per disk.