Liquid and droplet flow and gating effects in polymer brush-coated nanochannels

CLAUDIO PASTORINO; KEVIN SPEYER

Córdoba

Congreso; II Brazil-Argentine Microfluidics Congress - V Congreso de Microfluídica Argentina; 2019

We study liquid flow through polymer brush-covered nannochannels for varying polymer stiffness. We characterize the flow of droplets and a continuous thread of liquid as functions of grafting density, solvent quality, and flow rate. For the case in which solvophobic polymers from opposite walls can interact within each other, we find a very interesting gating phenomenon in which liquid flows with difficulty through the channel (closed gate) until a threshold of liquid driving, beyond which polymers move towards the channel walls, favoring a much higher flow rate (open gate). We performed molecular dynamics simulations with a coarse-grained model for the description of the polymers, accounting for chain connectivity, excluded volume interactions and bending rigidity. We use the dissipative particle dynamics thermostat to account for temperature conservation in steady state flow. We also analyse the flow properties of liquid droplets in coexistence with a vapor phase and the effects of the liquid-brush interactions and flow of droplet in cylindrical nanochannels.