5 May 2012 Combining digital holographic microscopy and optical tweezers: a new route in microfluidic
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Proceedings Volume 8430, Optical Micro- and Nanometrology IV; 84300W (2012); doi: 10.1117/12.922894
Event: SPIE Photonics Europe, 2012, Brussels, Belgium
Abstract
An optical configuration is realized to obtain quantitative phase-contrast maps able to characterize particles floating in a microfluidic chamber by interference microscopy. The novelty is the possibility to drive the sample and measure it thorough the same light path. That is realized by an optical setup made of two light beams coming from the same laser source. One beam provides the optical forces for driving the particle along the desired path and, at same time, it works as object beam in the digital holographic microscope (DHM). The second one acts as reference beam, allowing recording of an interference fringe pattern (i.e., the digital hologram) in an out-of-focus image plane. This work finds application in the field of micromanipulation as, the devise developed allows to operate in microfluidic chambers driving samples flowing in very small volumes. Recently, the field of optical particle micro-manipulation has had rapid growth, due to Optical Tweezers development. A particle is trapped or moved along certain trajectories according to the intensity and phase distribution of the laser beam used. Here, particles freely floating are driven by optical forces along preferential directions and then analyzed by a DHM to numerically calculate their phase-contrast signature. The improvement is that one laser source is employed for making two jobs: driving and analyze the sample. We use two slightly off-axis laser beams coming from a single laser source. The interference between them gives the possibility to record in real-time a sequence of digital holograms, while one of the beam creates the driving force. By this method, a great amount of particles can be analyzed by a real-time recording of DH movies. This allows one to examine each particle at time and characterize it. The optical configuration and the working method are illustrated. Experimental results are shown for polymeric particles and in-vitro.
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L. Miccio, P. Memmolo, F. Merola, M. Paturzo, A. Finizio, S. Grilli, P. Ferraro, "Combining digital holographic microscopy and optical tweezers: a new route in microfluidic", Proc. SPIE 8430, Optical Micro- and Nanometrology IV, 84300W (5 May 2012); doi: 10.1117/12.922894; https://doi.org/10.1117/12.922894
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KEYWORDS
Particles

Digital holography

Holography

Microfluidics

Holograms

Laser sources

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