Adaptive coatings based on polyaniline for direct 2D observation of diffusion processes in microfluidic systems

• Published in: Sensors and actuators. B, Chemical Chemical, 2016-08, Vol.231, p.744-751
• Main Authors: Florea, Larisa, Martin-Mayor, Alain, Bou-Ali, M.Mounir, Meagher, Kate, Diamond, Dermot, Tutar, Mustafa, Benito-Lopez, Fernando
• Format: Article
• Language: English
• Subjects: Adaptive coatings; Coatings; Computational fluid dynamics (CFD); Correlation; Devices; Diffusion; Diffusion coatings; Mathematical models; Microfluidics; Mixing process; Navier-Stokes equations; Optical sensor; Polyaniline
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2016.03.085

Polyaniline coated microfluidic channels allow for direct visualisation of diffusion dynamics and complete mixing point of solutions of different pHs. [Display omitted] •Colour-changing polyaniline coatings for direct 2D observation of diffusion in microfluidic systems.•2D optical monitoring of diffusion processes inside microfluidic channels.•Monitoring mixing in a dye free environment. Microfluidic devices are poised to dramatically influence the future of the process industry. Therefore the understanding and proper evaluation of the flow and mixing behaviour at microscale becomes a very important issue. In this study, the diffusion behaviour of two reacting solutions of HCl and NaOH were directly observed in a glass/polydimethylsiloxane microfluidic device using adaptive coatings based on the conductive polymer polyaniline that are covalently attached to the microchannel walls. The two liquid streams were combined at the junction of a Y-shaped microchannel, and allowed to diffuse into each other and react. The results showed excellent correlation between optical observation of the diffusion process and the numerical results. A numerical model which is based on finite volume method (FVM) discretisation of steady Navier-Stokes (fluid flow) equations and mass transport equations without reactions was used to calculate the flow variables at discrete points in the finite volume mesh element. The high correlation between theory and practical data indicates the potential of such coatings to monitor diffusion processes and mixing behaviour inside microfluidic channels in a dye free environment.