title: Generation and mixing of subfemtoliter aqueous droplets on demand.
abstract: We describe a novel method of generating monodisperse subfemtoliter aqueous droplets on demand by means of piezoelectric injection. Droplets with volumes down to 200 aL are generated by this technique. The droplets are injected into a low refractive index perfluorocarbon so that they can be optically trapped. We demonstrate the use of optical tweezers to manipulate and mix droplets. For example, using optical tweezers we bring two droplets, one containing a calcium sensitive dye and the other calcium chloride, into contact. The droplets coalesce with a resulting reaction time of about 1 ms. The monodispersity, manipulability, repeatability, small size, and fast mixing afforded by this system offer many opportunities for nanochemistry and observation of chemical reactions on a molecule-by-molecule basis.
authors.affiliation: Physics Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: Jianyong
authors.initials: J
authors.lastname: Tang
authors.forename: Ana M
authors.initials: AM
authors.lastname: Jofre
authors.forename: Rani B
authors.initials: RB
authors.lastname: Kishore
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Reiner
authors.forename: Mark E
authors.initials: ME
authors.lastname: Greene
authors.forename: Geoffrey M
authors.initials: GM
authors.lastname: Lowman
authors.forename: John S
authors.initials: JS
authors.lastname: Denker
authors.forename: Christina C C
authors.initials: CC
authors.lastname: Willis
authors.forename: Kristian
authors.initials: K
authors.lastname: Helmerson
authors.forename: Lori S
authors.initials: LS
authors.lastname: Goldner