In-Situ Formation of a Gel Microbead for Laser Micromanipulation of Microorganisms, DNA, and Viruses

We propose in situ formation of gel microbeads made of a thermoreversible hydrogel for indirect laser micromanipulation of microorganisms, DNA and viruses. Irradiation, using a 1064 nm laser, of an aqueous solution mixed with poly-(N-isopropylacrylamide) through a high magnification lens resulted in the formation of a gel microbead at the laser focus due to heating. The gel microbead was trapped by the laser, and was used for indirect laser micromanipulation of microscale and nanoscale samples. Laser tweezers can typically handle a microscale object with size ranging from several tens of nm to several hundreds of mum in a stable manner. However, a nanoscale object with a size of a few nm cannot be stably manipulated, and laser beam heating is a major problem. This paper shows a method of indirect manipulation of microorganisms, DNA and viruses using a gel microbead made from the poly-(N-isopropylacrylamide) aqueous solution. We succeeded in reducing the laser power for gel microbead formation, and in using the laser-trapped gel microbead for the manipulation of microorganisms, DNA and viruses