RSC Publishing


Publishing

 

Cover image for Lab on a Chip, select for current issue

Lab on a Chip

Microfluidic & nanofluidic technologies for chemistry, physics, biology, and bioengineering



Subscribers

Non-subscribers

Free access



Paper

Lab Chip, 2009, 9, 3289 - 3296, DOI: 10.1039/b906514h

Microfluidics with on-line dynamic light scattering for size measurements

Fanny Destremaut, Jean-Baptiste Salmon, Ling Qi and Jean-Paul Chapel

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 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.

Graphical abstract image for this article (ID: b906514h)