Superamphiphobic membranes for gas exchange and scrubbing

Porous polymer membranes are also used in various gas scrubbing applications. For example, acidic gases such as CO₂, SO₂ and H₂S are extracted from process and waste gases by contacting these gases via a gas-permeable membrane with a liquid medium such as an aqueous  solution of amines which is capable to absorb the acidic gases. The gas-exchange capacity of these membranes tends to be impaired by the insufficient chemical long-term resistance of most of the polymeric membranes commercially available and also by a gradual wetting of the membranes which increases the resistance to mass transfer and may decrease the process efficiency dramatically.

Another important application of polymer membranes is the process of blood oxygenation in heart-lung machines. Unfortunately, all synthetic materials display a more or less pronounced incompatibilty with blood. Contact with the artificial surface can induce hemolysis, protein denaturation and platelet and leukocyte damage and thrombosis. The resulting deposition of fibrin or platelets on the surface of the membrane greatly reduces the gas exchange rate.

Easy-to-fabricate oil- and water-repellent superamphiphobic coatings are made from soot encased in a silica shell ^[1]. The coating is sufficiently oil-repellent to cause the rebound of impacting drops of hexadecane. The coating is transparent and can be applied to a variety of heat-resistant surfaces, such as aluminum, copper, or stainless steel.

Novel gas exchange membranes based on superamphiphobic
coatings applied on metal meshes were created and tested in
different industrial applications.

By using the novel membrans drawbacks of traditional
membranes - like insufficient wetting, plugging and depositions
chemical incompatibility and temperature instability -
can be avoided.

Possible applications of the novel membranes:

• gas scrubbing (e.g. SO₂, SO₃ and H₂S, HCl, HCN, TiCl₄, TEOS etc.)
• CO₂ amine wash
• gas drying

Example:

A very efficient gas exchange through the superamphiphobic membrane could be shown.

For the application of the novel membranes in the blood oxygenation in heart-lung machines, the compatibilty with blood is an important property.

A superamphiphobic modified stainless steel mesh was brought into contact with human whole blood. After a predetermined time the whole blood was removed and the protein adhesion on the surfaces was quantified by the known Pierce Test. The values for coated and uncoated meshes can be compared since coated and uncoated meshes are about equal in mass. A significantly reduced protein adhesion could be observed for the superamphi-phobic mesh.

M. Paven, P. Papadopoulos, S. Schoettler, X. Deng, V. Mailaender, D. Vollmer, H-J Butt: "Super liquid-repellent gas membranes for carbon dioxide capture and heart-lung machines", Nature Communications (2013), 4, 3512, 6 pp
P. Papadopoulos, D. Vollmer, H-J Butt: "Super liquid-repellent layers: The smaller the better", Advances in Colloid and Interface Science, Volume 222, August 2015, Pages 104-109

US9901885 and EP2934728B1 (in DE, FR, GB) granted