title: Droplet-based microfluidics at the femtolitre scale.
abstract: We have built a toolbox of modules for droplet-based microfluidic operations on femtolitre volume droplets. We have demonstrated monodisperse production, sorting, coalescence, splitting, mixing, off-chip incubation and re-injection at high frequencies (up to 3 kHz). We describe the constraints and limitations under which satisfactory performances are obtained, and discuss the physics that controls each operation. For some operations, such as internal mixing, we obtained outstanding performances: for instance, in 75 fL droplets the mixing time was 45 μs, 35-fold faster than previously reported for a droplet microreactor. In practice, in all cases, a level of control comparable to nanolitre or picolitre droplet manipulation was obtained despite the 3 to 6 order of magnitude reduction in droplet volume. Remarkably, all the operations were performed using devices made using standard soft-lithography techniques and PDMS rapid prototyping. We show that femtolitre droplets can be used as microreactors for molecular biology with volumes one billion times smaller than conventional microtitre plate wells: in particular, the Polymerase Chain Reaction (PCR) was shown to work efficiently in 20 fL droplets.
authors.affiliation: Microfluidics, MEMS and Nanostructures Laboratory (MMN), CNRS UMR 7083, École supérieure de physique et de chimie industrielles de la Ville de Paris (ESPCI ParisTech), 10, rue Vauquelin, 75231 Paris Cedex 05, France. patrick.tabeling@espci.fr marie.leman@espci.fr.
authors.forename: Marie
authors.initials: M
authors.lastname: Leman
authors.forename: Faris
authors.initials: F
authors.lastname: Abouakil
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Griffiths
authors.forename: Patrick
authors.initials: P
authors.lastname: Tabeling
mesh_terms: D046210:Microfluidic Analytical Techniques / Q000295:instrumentation; D010316:Particle Size; D016133:Polymerase Chain Reaction; D013499:Surface Properties; D013816:Thermodynamics