Proceedings Article | 9 May 2012
KEYWORDS: Microfluidics, Particles, Digital holography, Microscopes, 3D image processing, Sensors, CCD image sensors, Holography, In vitro testing, Digital imaging
A compact twin-beam interferometer that can be adopted as a flexible diagnostic tool in microfluidic platforms is
presented. The devise has two functionalities, as explained in the follow, and can be easily integrated in microfluidic
chip. The configuration allows 3D tracking of micro-particles and, at same time, furnishes Quantitative Phase-Contrast
maps of tracked micro-objects by interference microscopy. Experimental demonstration of its effectiveness and
compatibility with biological field is given on for in vitro cells in microfluidic environment.
Nowadays, several microfluidic configuration exist and many of them are commercially available, their development is
due to the possibility for manipulating droplets, handling micro and nano-objects, visualize and quantify processes
occurring in small volumes and, clearly, for direct applications on lab-on-a chip devices.
In microfluidic research field, optical/photonics approaches are the more suitable ones because they have various
advantages as to be non-contact, full-field, non-invasive and can be packaged thanks to the development of integrable
optics. Moreover, phase contrast approaches, adapted to a lab-on-a-chip configurations, give the possibility to get
quantitative information with remarkable lateral and vertical resolution directly in situ without the need to dye and/or kill
cells. Furthermore, numerical techniques for tracking of micro-objects needs to be developed for measuring velocity
fields, trajectories patterns, motility of cancer cell and so on.
Here, we present a compact holographic microscope that can ensure, by the same configuration and simultaneously,
accurate 3D tracking and quantitative phase-contrast analysis. The system, simple and solid, is based on twin laser beams
coming from a single laser source. Through a easy conceptual design, we show how these two different functionalities
can be accomplished by the same optical setup. The working principle, the optical setup and the mathematical modeling
for 3D tracking is described. Finally, the experimental proof is presented and discussed for in vitro cells in microfluidic
chamber.
