Microfluidics with on-line dynamic light scattering for size measurements.
We present a detailed investigation on the feasibility of on-line dynamic light scattering measurements of colloidal sizes in a pressure-driven microfluidic flow. We review some theoretical arguments showing that such experiments are difficult to perform due to the Poiseuille flow that induces interferences of different Doppler shifts. Such a theoretical approach is however very useful to figure out the range of parameters where on-line size measurements are possible. We then build a dynamic light scattering setup around a microfluidic chip that enables us to estimate the size of Brownian scatterers flowing in PDMS-based microchannels, thus validating experimentally the theoretical estimations. We finally present a microfluidic chip that can mix two reactants in approximately 200 ms, and allows size measurements using dynamic light scattering at about 300 ms after complete mixing. Two applications are presented: the continuous monitoring of the viscosity of a two-fluid mixture, and the electrostatic co-assembly of oppositely charged nanoparticles and block copolymers.
LOF, UMR 5258 Rhodia-CNRS-Bordeaux 1, 178 avenue du Docteur Schweitzer, F-33608 Pessac cedex, France. fanny.destremaut-exterieur@eu.rhodia.com
Fanny
F
Destremaut
Jean-Baptiste
JB
Salmon
Ling
L
Qi
Jean-Paul
JP
Chapel
D003102:Colloids / Q000737:chemistry; D056656:Lab-On-A-Chip Devices; D008027:Light; D046208:Microchip Analytical Procedures / Q000379:methods*; D044085:Microfluidics / Q000295:instrumentation / Q000379:methods*; D010316:Particle Size; D012542:Scattering, Radiation
D003102:Colloids