Microfluidic osmotic compression of a charge-stabilized colloidal dispersion: Equation of state and collective diffusion coefficient

We show, using a model coupling mass transport and liquid theory calculations for a charge-stabilized colloidal dispersion, that diffusion significantly limits measurement times of its equation of state (EOS), osmotic pressure vs composition, using the osmotic compression technique. Following this result, we present a microfluidic chip allowing one to measure the entire EOS of a charged dispersion at the nanoliter scale in a few hours. We also show that time-resolved analyses of relaxation to equilibrium in this microfluidic experiment lead to direct estimates of the collective diffusion coefficient of the dispersion in Donnan equilibrium with a salt reservoir.

Automated summary

This study demonstrates that diffusion significantly limits the measurement times of the equation of state of charge-stabilized colloidal dispersions, and presents a microfluidic chip that can measure the entire equation of state at the nanoliter scale in a few hours. Time-resolved analyses of relaxation to equilibrium in this microfluidic experiment also provide direct estimates of the collective diffusion coefficient of the dispersion in Donnan equilibrium with a salt reservoir.