title: Fluid mixing in growing microscale vesicles conjugated by surfactant nanotubes.
abstract: This work addresses novel means for controlled mixing and reaction initiation in biomimetic confined compartments having volume elements in the range of 10(-12) to 10(-15) L. The method is based on mixing fluids using a two-site injection scheme into growing surfactant vesicles. A solid-state injection needle is inserted into a micrometer-sized vesicle (radius 5-25 microm), and by pulling on the needle, we create a nanoscale surfactant channel connecting injection needle and the vesicle. Injection of a solvent A from the needle into the nanotube results in the formation of a growing daughter vesicle at the tip of the needle in which mixing takes place. The growth of the daughter vesicle requires a flow of surfactants in the nanotube that generates a flow of solvent B inside the nanotube which is counterdirectional to the pressure-injected solvent. The volume ratio psi between solvent A and B inside the mixing vesicle was analyzed and found to depend only on geometrical quantities. The majority of fluid injected to the growing daughter vesicle comes from the pressure-based injection, and for a micrometer-sized vesicle it dominates. For the formation of one daughter vesicle (conjugated with a 100-nm radius tube) expanded from 1 to 200 microm in radius, the mixing ratios cover almost 3 orders of magnitude. We show that the system can be expanded to linear strings of nanotube-conjugated vesicles that display exponential dilution. Mixing ratios spanning 6 orders of magnitude were obtained in strings of three nanotube-conjugated micrometer-sized daughter vesicles.
authors.affiliation: Department of Physical Chemistry and Microtechnology Centre, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
authors.forename: Max
authors.initials: M
authors.lastname: Davidson
authors.forename: Paul
authors.initials: P
authors.lastname: Dommersnes
authors.forename: Martin
authors.initials: M
authors.lastname: Markström
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Joanny
authors.forename: Mattias
authors.initials: M
authors.lastname: Karlsson
authors.forename: Owe
authors.initials: O
authors.lastname: Orwar
mesh_terms: D005456:Fluorescent Dyes / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry; D008956:Models, Chemical; D043942:Nanotubes / Q000737:chemistry*; D037121:Plant Lectins / Q000737:chemistry*; D030262:Soybean Proteins / Q000737:chemistry*; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D010835:Phytohemagglutinins
chemical_list: D005456:Fluorescent Dyes; D008081:Liposomes; D037121:Plant Lectins; D030262:Soybean Proteins; D013501:Surface-Active Agents; C028824:soybean lectin; D010835:Phytohemagglutinins