From Event: SPIE Nanoscience + Engineering, 2019
In the last three decades, optical trapping techniques were heavily employed for contactless trapping and manipulation of biological samples. Dual-beam laser traps (DBLT) proved their convenience and became widely used as biophysical tool once a simplified experimental setup was proposed. This simplification was achieved by replacing the two objectives with optical fibers to deliver the two counter-propagating laser beams. However, fiber alignment can be inconvenient, time consuming and requires a lot of practice. Here, we present a novel way to overcome these issues by combining reconfigurable diffractive optical elements (DOE) and two photon lithography (2PL), using a single low NA objective. A single laser beam is divided into several beams by displaying a DOE on a spatial light modulator (SLM). This allows us to dynamically reconfigure the number of the beams, their shape, and relative 3D alignment. Furthermore, we use 3D printed micro-mirrors to direct the laser beams against each other and obtain a DBLT. The micro-mirrors were fabricated on top of a coverslip, by means of 2PL. Our preliminary results show the ability to trap dielectric and biological samples and their full 3D manipulation in a DBLT configuration. The ability to use DOEs to set the number of beams and their shape allow this technique to be coupled with novel forms of microscopy.
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Gheorghe Cojoc, Andrea Bertoncini, Paul Müller, Jochen Guck, and Carlo Liberale, "Optical trapping and manipulation with a low NA objective through 3D printed micro-mirrors (Conference Presentation)," Proc. SPIE 11083, Optical Trapping and Optical Micromanipulation XVI, 110830C (Presented at SPIE Nanoscience + Engineering: August 11, 2019; Published: 9 September 2019); https://doi.org/10.1117/12.2529532.6083789092001.