Probing Molecular Transport through Polymer Brushes: A Fluorescence View of Brush Functionalised Microfluidics

• Applicant: László Mérai, Ph.D.
• Subject Area: Polymer Materials ; Synthesis and Properties of Functional Materials ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Preparatory and Physical Chemistry of Polymers
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 557863302

Material transport within thin polymer films and polymer brushes is of high interest in regards of various fundamental aspects and practical applications, including molecular transport in biological systems [1], nanomedicine [2], fouling reduction [3] and selective filtration [4]. As in most of these systems, the polymer brushes are located in flow channels, or at least, their overall behaviour is affected by convective flow of some sort, therefore, understanding the molecular transport-flow relations is of vital importance. While the related literature has mainly been focusing on theoretical and single-molecule tracking approaches, and experimentation on systems with highly specific boundary or no-flow conditions, a real-time, larger-scale spatially-resolved visual approach, that is capable of monitoring the molecular transport within brushes decorating practical microfluidics is still missing. To fill this gap, and to move the field forward, this proposal aims to study material transport phenomena in polymer brushes decorating microfluidic channels by utilising fluorescence coupling between brush-bound and free-moving solute fluorophores. As very recently established, the phenomenon of Förster resonance energy transfer (FRET) in combination with confocal laser scanning microscopy (CLSM) detection can provide high-resolution (~200 nm spatial resolution) visual information on local brush conformation [5] and brush-solute interactions [6,7]: by adapting these measurements to microfluidic devices, my aim is to directly visualise the diffusive and convective transport of different FRET-acceptor solutes parallelly and vertically to the substrate surface through FRET-donor functionalised thermoresponsive poly(N-isopropyl acrylamide)-based polymer brushes. The proposed methodology allows for the investigation of the relations among transport phenomena, brush properties (such as height, density and conformation), solute size, temperature and flow conditions (flow rate, channel architecture). These experiments are prospected to provide new fundamental insight into the operation of polymer brush-decorated microchannels, paving the way towards new fundamental insights and to the development of such practical systems with improved performance. 21)

• DFG Programme: WBP Position