Debye lunch lecture - Henrik Siegel MSc

Synthesis and formation mechanisms of nanoparticle-stabilized emulsion gels for membrane separations

Climate change and population growth are putting immense pressure on water resources. To produce clean water for daily life, porous separation membranes are needed. However, traditional separation membranes made of polymers are susceptible to fouling and chemical degradation, compromising filtration properties. Recently, bicontinuous interfacially jammed emulsion gels (bijels) have been introduced as robust membrane material with nanoparticle-covered surfaces that enhance stability. However, their formation via liquid/liquid phase separation and nanoparticle self-assembly involves complex interfacial stabilization mechanisms, which need to be controlled to produce bijel separation membranes.

We hypothesize that surface tension and particle wettability are the key drivers in interfacial bijel stabilization. To test our hypothesis, we study the effect of liquid composition on surface tension and particle self-assembly during bijel synthesis via solvent transfer induced phase separation (STrIPS) [1]. Revealing how the liquid composition governs the bijel structure, the fabrication of bijels via roll-to-roll film coating is introduced [2]. As these STrIPS-bijel films are made using surfactant-modified nanoparticles, we detail how the simultaneous presence of surfactants and particles at liquid/liquid interfaces affects the rigidity of colloidal assemblies in bijel stabilization [3]. To refine control over the bijel structure in roll-to-roll coating, we analyze how substrate wetting affects the membrane uniformity [4]. The resulting fundamental insights into the self-assembly and bijel formation kinetics allow us to demonstrate the application of bijels for filtration with controlled selectivity and pH-responsive flux.

Publications

[1] H. Siegel, A. J. Sprockel, M. S. Schwenger, J. M. Steenhoff, I. Achterhuis, W. M. de Vos, M. F. Haase (2022). Synthesis and Polyelectrolyte Functionalization of Hollow Fiber Membranes Formed by Solvent Transfer Induced Phase Separation. ACS Applied Materials & Interfaces 14 (38), 43195 – 43206.

[2] H. Siegel, M. de Ruiter, G. Athanasiou, C. Hesseling, M. F. Haase (2024). Roll-to-Roll Fabrication of Bijels via Solvent Transfer Induced Phase Separation (R2R-STrIPS). Advanced Materials Technologies 9 (3), 2301525.

[3] H. Siegel, M. de Ruiter, T. H. R. Niepa, M. F. Haase (2025). The effect of charge screening for cationic surfactants on the rigidity of interfacial nanoparticle assemblies. Journal of Colloid and Interface Science 678 (Part A), 201 – 208.

[4] H. Siegel, M. F. Haase (2024). Bijel-templated hydrogel membranes for pH-responsive water filtration. Preprint on ChemRxiv, under review.