Abstract
We have developed norland optical adhesive (NOA) flow focusing devices, making use of the excellent solvent compatibility and surface properties of NOA to generate micron scale oil-in-water emulsions with polydispersities as low as 5%. While current work on microfluidic oil-in-water emulsification largely concerns the production of droplets with sizes on the order of 10s of micrometres, large enough that Brownian motion is negligible, our NOA devices can produce droplets with radii ranging from 2 μm to 12 μm. To demonstrate the utility of these emulsions as colloidal model systems we produce fluorescently labelled polydimethylsiloxane droplets suitable for particle resolved studies with confocal microscopy. We analyse the structure of the resulting emulsion in 3D using coordinate tracking and the topological cluster classification and reveal a new mono-disperse thermal system.
Highlights
We have developed norland optical adhesive (NOA) flow focusing devices, making use of the excellent solvent compatibility and surface properties of NOA to generate micron scale oil-in-water emulsions with polydispersities as low as 5%
We describe the structural insights obtained from using the topological cluster classification algorithm for probing the structure of an emulsion, and our results are compared to a simulated hard sphere system
NOA channels were made hydrophilic by exposing the device layer to a 100 W oxygen plasma for 60 seconds, and the channel geometry was enclosed by sealing the NOA chip with a thin layer of NOA produced by pressing several droplets of NOA between two clean sheets of PDMS and UV curing for 2 minutes
Summary
We have developed norland optical adhesive (NOA) flow focusing devices, making use of the excellent solvent compatibility and surface properties of NOA to generate micron scale oil-in-water emulsions with polydispersities as low as 5%. Given the considerable amount of interest in emulsions, it should come as no surprise that the formation of emulsions is a well explored field with a huge range of emulsification techniques available These methods include such techniques as mechanical milling, blending, high pressure homogenization, or shear mixing. An alternative to the aforementioned methods is microchannel emulsification, a versatile technique where two or more distinct fluid phases are flowed through a microscale channel and interfacial stresses are induced to generate droplets with very narrow size distributions.[14] Currently microfluidic emulsification techniques remain focussed primarily on the formation of water-in-oil emulsions, usually with the viscosity ratio l below 1. In order to develop the desired colloidal model system we must first consider the behaviour of a droplet in solution using the Peclet number Pe = tB/tsed. It is vital that a microfluidic system for the production of colloidal oil-in-water emulsions is capable of both producing droplets which are suitably small and uniform, and to be solvent-compatible enough to produce emulsions from a range of component materials
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
