Surface modification of Microsieves

Modified Silicon nitride surfaces for food applications

Microsieves are a new kind of membranes, which could be used for purification and structuring of bio-materials. They are prepared by means of photo-lithographical techniques, allowing considerable degrees of freedom in the design of the sieve (size, geometry and positioning of pores). Further, they are extremely thin and flat, and as a result have a very low flow resistance. The water fluxes of microsieves are, typically, 100-1000 fold higher than water fluxes of traditional membranes. Typical microsieve structures are shown in Figure 1.
Fig. 1 SEM picture of microsieves with uniform pores (photo courtesy of Aquamarijn B.V.)

Aim of the project
Microsieves still suffer from undesired interactions with components (fouling) and surface properties that change in time. Our goal is to generate and study tailor-made surfaces for microsieves, and implement these in a working processing set-up. To this aim, extensive collaboration between organic surface science and bioprocess engineering is needed.

A first approach is to covalently bind monolayers of organic molecules to the silicon nitride surface of microsieves. In previous work, a very efficient 2-step thermal method has been developed (see figure 2), allowing covalent bonding of 1-alkenes and 1-alkynes on silicon nitride surfaces, through surface etching by dilute HF solution and reaction with the molecule to be grafted. This method resulted in stable modified surfaces.
Fig. 2 Formation and further functionalization of covalently attached monolayers of hydrogen-terminated silicon nitride.

Future research
We have to investigate more about properties of silicon nitride surfaces (composition, roughness, reactivity). Stability of attached monolayers is an important issue for further applications in processes.

  • Covalent Biofunctionalization of Silicon Nitride Surfaces. Ahmed Arafat, Marcel Giesbers, Michel Rosso, Ernst J. R. Sudhölter, Karin Schroën, Richard G. White, Li Yang, Matthew R. Linford, and Han Zuilhof. (2007) Langmuir 23, 6233-6244 Abstract; Full Text (PDF)