Freeform Membranes with Tunable Permeability in Microfluidics

Abstract Microfluidic systems offer a multitude of advantages over classical techniques in the fields of biomedical and chemical research. Unit operations such as sample pre‐treatment, mixing, reactions, and especially separation and purification operations can be realized on microfluidic platforms enabling rapid prototyping and facile parallelization on the laboratory scale. However, the fabrication and integration of porous membranes in microfluidics poses several problems. Material development, membrane geometry, and membrane integration are three main questions to be addressed in this context. Herein, a durable and versatile method to anchor free‐form membranes with tunable microgeometry to surfaces, enabling the fabrication of stable, multi‐material microfluidic systems for different potential applications is shown. In addition, the influence of the macro‐ and microgeometry that is the shape and porosity of a membrane on key performance indicators such as diffusivity and permeation of tracer molecules is investigated. The presented characterization methods will enable a better understanding of microfluidic modules with incorporated membranes.