Optolab.IAI, within a joint R&D effort involving Institute of Condensed Matter Physics of EPFL, the Biozentrum of Basle University and the startup company Ninart, has developed and built the prototype of a novel optical tracking interferometry microscope. This may be seen as a variant of photonic force microscope. The current phase of the project is sponsored by the Swiss National Science Fundation.
This type of instrument uses particles subjected to Brownian motion as a reporter of the local environment. With this approach any deviation from the normal diffusive behavior of the particle can be interpreted as a response to the material properties of its complex environment. To measure such behavior, a high spatial resolution down to the nanometer scale is provided by the instrument.
Tracking a single particle in a fluid on time scales sufficiently short to detect hydrodynamic contributions can be realized by Optical Tracking Interferometry (OTI). OTI utilizes a weak optical trap and interferometric particle position detection. The trapping laser provides a light source for the position detection of the particle and at the same time ensures that the particle remains within the detector range.
The essential schematic of the instrument comprises a custom-built inverted light microscope with a 3D sample positioning stage, an infrared laser for trapping, and a quadrant photodiode for high–resolution three-dimensional and time-resolved position detection. However the instrument also includes various other features not shown here.