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ERC

SuPro Report Summary

Project ID: 340391
Funded under: FP7-IDEAS-ERC
Country: Germany

Mid-Term Report Summary - SUPRO (Superamphiphobic surfaces for chemical processing)

The objective of this proposal is to explore the potential of novel superamphiphobic (water and oil repellent) surfaces for applications in chemical processing. Specific goals are
• to design efficient gas-liquid contactor membranes;
• to make microspheres on demand as an example for green, solvent-free synthesis;
• to achieve reduced hydro¬dynamic drag in micro¬fluidics;
• to fabricate anti-biofouling coatings.
These ambitious goals are based on two enabling objectives:
• a better fundamental understanding of the wetting properties of superamphiphobic layers;
• develop and improve methods to make robust liquid-repellent surfaces.
With respect to all objectives we made significant progress.
Gas membranes. We introduced superamphiphobic membranes for enhanced CO2 absorption (Geyer et al., Adv. Materials 2016, in press). On superamphiphobic membranes the aqueous alkanolamine solution used for CO2 capture stays on the topmost part of the membrane. Wetting of the pores in the membrane is prevented. As it turned out, amine solutions are highly corrosive. Therefore we had to develop a novel concept to fabricate gas membranes. Key was (1) to use polymeric rather than metallic carrier materials, (2) coat surfaces with nano¬fila¬ments and (3) coat the nanofilaments with perfluoro-alkyl¬silanes. The CO2 capture rates of our superamphiphobic membranes were enhanced by more than 20% relative to state-of-the-art commercial membranes with no decay within 50 hours.
Microsphere on demand. We demonstrated a generalized fabrication process for mesoporous supraparticles on superamphiphobic surfaces (Adv. Mater. 2015, 27, 7338). Therefore, we let drops of nanoparticle dispersions evaporate from the superamphiphobic surface. This leads to the formation of spherical mesoporous supraparticles which can be removed easily from the surface. Avoiding solvents prevents the contamination of the continuous phase by side products and organic auxiliaries such as templating surfactants, or stabilizers, starting compounds etc. Also a time-consuming or costly purification of the continuous aqueous phase is not required.
Microchannels. Meanwhile we characterized the effect of surfactants on hydrodynamic drag reduction on superhydrophobic surfaces (Phys. Rev. Lett. 2016, 116, 4501). In contrast to clean water, in which superhydrophobic surfaces reduce hydrodynamic drag, the presence of even trace amounts of surfactants leads to an effective no-slip boundary condition. Reason is a Marangoni effect. After several attempts to coat microcapillaries from the inside with super¬amphi¬phobic surface we now established a procedure.
Antibiofouling. By X-ray photoelectron spectroscopy and time of flight secondary ion mass spectro¬me-try analysis we found that the high blood compatibility and antibiofouling property of soot-tem¬pla¬ted superamphiphobic surfaces is due to extremely low protein adsorption (Biointerphases 2016, 11, 031007); protein adsorption is usually the first step in biofilm formation.
Fundamental understanding of the wetting process. A real breakthrough was our proof that advancing and receding contact angles on superhydrophobic surfaces not merely reflect slight deviations from a thermodynamically stable state. Using confocal microscopy we demonstrated that the processes of an advancing liquid front is fundamentally different than the recession of a liquid front (Phys. Rev. Lett. 2016, 116, 096101, highlighted by Nature Materials 2016, 15, 376). In contrast to common belief, the liquid surface gradually bends down until it touches the top face of the next micropillars. On the receding side, pinning to the top faces of the micropillars determines the apparent receding contact angle. We propose that the apparent receding contact angle should be used for characterizing super liquid-repellent surfaces, rather than the apparent advancing contact angle and hysteresis.

Contact

Zsolt Tóvári, (Head of Staff Unit Managing Director)
Tel.: +49 6131 379411
Fax: +49 6131 379361
E-mail
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