The membrane is dripping from the needle – Science – Kommersant

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Scientists from the A.V. Topchiev Institute of Petrochemical Synthesis (TIPS) of the Russian Academy of Sciences applied the principle of operation of 3D printers to quickly obtain test samples of hollow fiber polymer membranes. This made it possible to reduce the consumption of materials and the time for obtaining samples, which reduced the cost of developing new membranes by 30 times. The study was supported by a grant from the Russian Science Foundation and published in the international journal Membranes.

Today, for the separation of liquid and gas mixtures, membranes are used – thin “barriers” that, like a molecular filter, allow only the necessary substances to pass through. They can be either flat or hollow-fiber, in the form of thin, hollow, porous or non-porous capillaries, the diameter of which is sometimes comparable to the thickness of a human hair. The main advantage of hollow fiber membranes is that they can be packaged very tightly in a small module. So, a module with a diameter of only 20 cm and a length of 1 m can contain thousands of fibers, and their total usable area is comparable to the area of ​​two volleyball courts.

Traditionally in industry, such membranes are produced by “immersion deposition”, in which a viscous solution of a membrane-forming polymer in an organic liquid is “pushed” through an annular slot of a special spinneret into a liquid – a precipitator. The solvent passes from the polymer solution to the precipitant, the polymer precipitates and forms a hollow fiber.

Various separation tasks (for example, for water purification or for air separation) often require the development of new membranes with the necessary transport and separation properties. For this, physicochemists thoroughly investigate and select such a combination of polymers, organic solvents, and precipitants, which will make it possible to form a membrane with the required structure and properties. This selection is complicated by the resource-intensive production of test samples of membranes in multifunctional research facilities that require a large consumption of materials. Often, new polymers, solvents, and precipitants are expensive to obtain, which, in turn, significantly affects the cost of developing new membranes.

Images of hollow fiber membrane samples made on the manipulator

Фото: T.Anokhina et al / Membranes

That is why scientists from the TIPS RAS (Moscow) were attracted by the principle of operation of 3D printers, namely the “Cartesian kinematics” of the print head movement, that is, the programmed movement of the head position relative to the printer platform along one or more of the three axes – X, Y, Z. This the principle formed the basis for the creation of a manipulator for obtaining samples of hollow fiber membranes based on a device for 3D printing. The researchers replaced the print head of the 3D printer with a syringe with a needle, and on the working platform they fixed a matrix with containers containing various versions of polymer solutions and precipitants. Setting the algorithm for the movement of the head and platform, the needle was sequentially lowered into the polymer solution, and then into the precipitator, thus obtaining fiber samples 35–75 mm long. This length is already sufficient to determine the transport and separation properties of future membranes.

This approach is so technically simple that in just 29 hours the authors managed to produce a series of representative samples of hollow fiber membranes from 12 polysulfone molding solutions, and the volumes of these solutions did not exceed 1 cubic meter. cm.

“Our method made it possible in the shortest possible time to select the optimal combination of polymer solution-precipitant for obtaining membranes with the required characteristics, which in the traditional version would take three weeks. The developed method makes it possible to significantly reduce the production time of new membranes and reduce the volume of polymer used, which makes this approach promising for the study of expensive or new membrane materials, ”commented the project manager Tatyana Anokhina, PhD in Chemistry, Researcher, Laboratory of Polymeric Membranes, TIPS RAS.

Использованы материалы статьи «Express Method of Preparation of Hollow Fiber Membrane Samples for Spinning Solution Optimization: Polysulfone as Example»; Tatyana Anokhina, Alisa Raeva, Sergey Makaev, Ilya Borisov, Vladimir Vasilevsky, Alexey Volkov; журнал Membranes, май 2021

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