Controllable membrane system for the separation of soft particles

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Separation and sorting of cells in complex fluids remain major challenges in life sciences and in various technical fields. Membranes with switchable pore properties qualify for this task due to the high parallelization potential of filtration and therefore high throughput. The present proposal of the Institute of Solid Mechanics and the Institute of Semiconductors and Microsystems at Technische Universität Dresden follows the concept of cell separation using permeation control in composite membranes. In the proposed system, a PET membrane is used as a backbone and is surface polymerized with a temperature sensitive poly(N-isopropylacrylamide) (PNIPAAm) hydrogel. Pores are inserted into this active structure by laser ablation. When a temperature stimulus is applied, the pores open and close due to hydrogel swelling. Thereby, we realize membranes with reproducibly switchable permeation properties. Preliminary studies have shown that the above described system can be realized. Additionally, we have demonstrated that numerical simulations with the Finite-Element-Method can be used to predict the pore opening behavior. Our model can therefore be used for optimizing the membrane system with respect to particle blocking and fluidic properties. Based on these studies, we aim to investigate at first a membrane system comprising a single switchable pore. Rigid model particles in microfluidic flow will be used to assess both the pore performance and the modeling predictions. According to the findings of envisaged simulative studies, the design of the membrane composite system has to be adapted to occurring effects. These can be particle-interactions and membrane deformation. The new design will then be used for experimental investigations of a multi-pore membrane. In case of successful development of the controllable multi-pore membrane composite system, we aim for extending our investigations to elastic particles. This would pave the way towards the development of a microfluidic cell separation system based on our approach.