Yasuyuki Tsuboi and Ken-ichi Yuyama (Osaka Metropolitan University) developed a novel technique to control the Förster resonance energy transfer (FRET), a phenomenon seen in photosynthesis and other natural processes where a donor molecule (D) in an excited state transfers energy to an acceptor molecule (A). By focusing a laser beam on an aqueous polymer solution, a single polymer droplet was produced and trapped (optical tweezer). D and A, fluorescent dye molecules, were extracted and condensed into the droplet in the solution. The authors showed that increased dye concentration accelerated the energy transfer, made visible by the polymer changing fluorescence color due to the dyes mixing. Fluorescence could also be controlled just by adjusting the laser intensity without touching the sample, offering a novel non-contact approach. The technique would be applied to optical vortex tweezers. A vortex beam can rotate the droplet, accelerating the extraction process to enhance FRET.
This work has been published in Advanced Optical Materials, on April 30th.

https://onlinelibrary.wiley.com/doi/10.1002/adom.202400302