Confinement and Manipulation of Individual Molecules in Attoliter Volumes

Abstract

We report observation of fluorescence from individual rhodamine 6G molecules in streams of charged 1-μm-diameter water droplets. With this approach, illumination volumes comparable to diffraction-limited fluorescence microscopy techniques (≤500 aL) are achieved, resulting in similarly high contrast between single-molecule fluorescence signals and nonfluorescent background. However, since the fluorescent molecules are confined to electrically charged droplets, in situ electrodynamic manipulation (e.g., focusing, switching, or merging) can be accomplished in a straightforward manner, allowing experimental control over both the delivery of molecules of interest to the observation region and the laser-molecule interaction time. As illustrated by photocount statistics that are independent of molecular diffusion and spatial characteristics of the excitation field, individual rhodamine 6G molecules in 1-μm droplets are reproducibly delivered to a target a few micrometers in diameter at a rate of between 10 and 100 Hz, with laser beam transit times more than 1 order of magnitude longer than diffusion-limited laser-molecule interaction times in equivalent volumes of free solution.

Self‐assembled organic nanotubes: Toward attoliter chemistry

“…To manipulate still ultrasmaller volumes of liquids in such diverse fields as cell biology, microfluidics, capillary chromatography, and nanolithography, one needs a better understanding of fluid behavior confined in attoliter volume. [1][2][3][4][5][6][7] Indeed, water in nanometer-sized restricted geometries, such as micelles and microemulsions, 8,9 nanometer films, 10,11 and nanoporous silica, 12 often shows different and sometimes unexpected features in comparison to bulk water. The trend of miniaturization in conventional microchip devices consisting of poly(dimethylsiloxane), silicone, and glass has thus directed growing attention to new femtoliter (fL ¼ 10 À15 L) or attoliter (aL ¼ 10 À18 L) vessels like carbon 13 and silica nanotubes.…”

Microfluidics for Processing Surfaces and Miniaturizing Biological Assays

“…[49][50][51][52][53][54][55] Secondly, the seminal work by Manz and co-workers on chip-based capillary electrophoresis [56,57] helped many concepts, such as lab-on-a-chip or micro-total analysis systems, [58][59][60][61][62][63][64] micro-flow injection analysis, [65] lab-ona-CD, [66][67][68] and microfluidic processors, [69] to emerge and find applications in analytical chemistry and biochemistry, diagnostics, [70] and research in life sciences. [71][72][73] These concepts come with various exciting flavors, such as parallelism, [74,75] fast time to result, [76][77][78][79][80] portability, [81][82][83] high sensitivity, [84] small volume of sample, [85] high-quality data, [57,86,87] heterogeneous phase reactions with large surface-to-volume ratios, [16] efficient particle/cell sorting, [88][89][90] or reactions done at liquid interphases. [...…”

Dynamic Pattern Formation in a Vesicle-Generating Microfluidic Device

“…Since geometric effects play a significant role in the pattern formation, one should be able to take advantage of the powerful microfabrication technology both to explore the consequences of this observation and to provide stringent tests of theoretical models. This system may also find application as a component in a microfluidic screening chip, since it has been shown that subnanoliter vesicles have significant potential as tools for screening of biological and synthetic compounds [14][15][16].…”