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.

Direct laser writing-enabled 3D printing strategies for microfluidic applications

“…[111][112][113] Although there are pathways to achieve basic "quasi-2.5D" geometries (e.g., microchannels with hemispherical cross sections, microchannels with different heights) via conventional means, [114][115][116] DLW affords far more expansive geometric versatility in the production of master moulds for microreplication. [117][118][119] Thus, one of the most straightforward routes to harness DLW for microfluidic applications is to use DLW to: (i) produce a master mould with features that would be difficult or infeasible to fabricate through standard microfabrication techniques (Fig. 2a), (ii) use the mould for microchannel replication (e.g., with PDMS) (Fig.…”

3D printed integrated nanoporous membranes for electroextraction of DNA

“…30 Using Fused Deposition Modelling (FDM) 3D printing, a size mobility trap was created using materials with approximately ∼12 and 1 nm pores, showing passage of fluorescein, but not bovine serum albumin (BSA) though the 12 nm pores. 32 As PEGDA-based PIPS materials are prone to swelling, 33 the desired average pore size for membrane 1 was set conservatively at ∼300 nm to ensure transport of DNA. While DNA is a macromolecule, its transport through nanometer sized channels and pores in an electric field has been demonstrated through uncoiling.…”

“…32 When printed between two electrolyte-filled chambers, however, no current was detected upon applying an electric field, suggesting ionic transport was blocked, possibly due to swelling of the PEGDA. 33 As a current was measured using the 50% (v/v), this formulation was selected for printing membrane 2.…”

3D Printing of Aqueous Two‐Phase Systems with Linear and Bottlebrush Polyelectrolytes

“…However, for Cases II (1.6×10 À 12 m 2 s À 1 ), III (3.0×10 À 12 m 2 s À 1 ) and IV (1.1×10 À 12 m 2 s À 1 ) the diffusion coefficient is one order magnitude smaller than the literature membrane diffusion coefficients and about two orders magnitude order smaller than in the bulk solution (Figure 6 and S18, S19, S20 and Table S5). [26,31,32] The data suggests that the L-PEC membrane behaves as a highly permeable structure, as the diffusion coefficient of RB is only slightly slower than the diffusion of L-PEC in bulk solution. On the other hand, the BB1-PEC membranes are less permeable, due to the more crowded complexes and structures formed within the membrane.…”