  We demonstrate a novel technique for creating, manipulating, and combining
femtoliter volume chemical containers. Possible uses include creating
controlled chemical reactions involving small quantities of reagent, and
studying the dynamics of single molecules within the containers by fluorescence
imaging techniques. The containers, which we call hydrosomes, are surfactant
stabilized aqueous droplets in a low index-of-refraction fluorocarbon medium.
The index of refraction mismatch between the container and fluorocarbon is such
that individual hydrosomes can be optically trapped by single focus laser
beams, i.e. optical tweezers. Here we trap and manipulate individual
hydrosomes. We demonstrate a controlled chemical reaction by the fusion of a
hydrosome containing DNA segments approximately 1000 base pairs in length with
a hydrosome containing YOYO-1, a DNA intercalating dye. We furthermore detect
the fluorescence from single dye molecules in a hydrosome, and observe single
pair fluorescence resonance energy transfer (spFRET) from Cy3-Cy5 molecules
attached to a single-stranded 16mer DNA molecule.
