Fast digital holography microscopy for optically trapped biosensor probes
Begeleider(s): ir. Stijn Vandewiele


In digital holography microscopy a hologram of a test subject is illuminated with a collimated, monochromatic light source. By capturing the light scattering pattern interfering with the original light beam on a digital video camera it is possible to extract phase information of the captured light. This powerful tool allows to reconstruct the electric field along the optical axis and hereby reconstructing a 3D image of the scattering subject. This results in information of the position, orientation and geometry of complex structures.

On the ohter hand, when holographic images are fitted to scattering simulations, extra and more accurate information of the position dependent refractive index of the subject is easily accessible. This allows us to measure nanometer-thick coatings on particles. One of the limiting factors is the slowness of this fitting process, however. Our group has therefore recently bought a fast GPU card enabling to speed up this process considerably.

An interesting application is to combine this tool with an optical tweezer to trap and characterize a biosensor and measure the dynamics of the reaction.


Figure: A biotinylated particle trapped in an optical tweezer. Avidin chemically binds with bioten forming a coating of avidin on the particle. [Image from Toon Brans]


Figure: Schematic of a holographic video microscopy setup where the scattering field of a particle is fitted to a measurement. [H. Shpaisman, , Applied Physics Letters 101, 091102 (2012).]


The goal of this master thesis involves different aspects:

First, you will adapt the current optical tweezer setup to enable digital holographic microscopy. This involves the choice of a good illumination source and an easy alignment method. You will also adapt and create software for the analysis of images and fitting of scattering problems for a graphics card. New algorithms will be investigated and developed to increase speed and/or accuracy. You will then use the setup to track the chemical binding of a biotinylated particle reacting with avidine, by measuring nanometer changes in the size of the particle. This project fits within both the biomedical and photonics clusters of Engineering Physics. 

The staff of the LCP group will provide you with all the necessary help and know-how, but we also encourage you to take the initiative to come up with your own ideas to tackle the project. Where feasible and within the scope of the project, we'll support you to develop these ideas.