Focusing and sorting polystyrene particles and liposomes via diffusiophoresis in flat microchannels Adnan Chakra 1,5 , Naval Singh 2 , Goran Vladisavljević 1 , François Nadal 3 , Cécile Cottin-Bizonne 4 , Christophe Pirat 4 and Guido Bolognesi 1,5 1 Loughborough University, UK, 2 University of Manchester, UK, 3 Commissariat à l'Energie Atomique (CEA), France, 4 Universit´e Claude Bernard Lyon 1, France, 5 University College London, UK We report a novel phenomenon that enables the pre-concentration and sorting of charged polystyrene particles and liposomes dispersed in a continuous flow within a straight flat microchannel. A 3-inlet junction microfluidic device is used to generate a steady-state salt concentration gradient in the direction perpendicular to the flow [1-4]. Particles dispersed in the electrolyte solution accumulate into two symmetric regions of the channel by forming two distinct focusing spots. Our numerical and experimental analysis shows that the observed particle dynamics is driven by an unreported physical mechanism, that combines diffusiophoresis, diffusioosmosis and hydrodynamics. Moreover, we developed a proof-of-concept microfluidic device that exploits this mechanism to enable focusing and filtration of particles based on their zeta potential and size under continuous flow settings. We show that our system can be used for the online characterisation of the aforementioned particle properties as well as the ability to detect the percentage of charged lipid present in the outer leaflet of liposomes. The proposed method offers potential for microfluidic bio-analytical testing applications References 1. Abecassis et al, Nature Materials, 2008, 7. 785-9. 10.1038 2. Singh et al, Phys Rev Lett, 2020, 125, 248002 3. Singh et al,Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2022, 652, 129808. 4. Singh et al,Langmuir, 2022,38(46), 14053-14062.
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