Leonard Kelley holds a bachelor's in physics with a minor in mathematics. He loves the academic world and strives to constantly explore it.
Oftentimes in material sciences we need to filter, isolate, or change objects, and membranes are a great way to accomplish this. Oftentimes challenges arise with them including manufacturing, durability, and achieving the desired results. So let’s take a look at how some of these hurdles have been overcome in the field of membrane technology.
Getting dust, allergens, and the like out of the air is a real challenge, so when scientists from the Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences announced a filter than is made of nylon nanofibers, it got people’s attention. The filters are only 10-20 milligrams per square meter and allow 95% of light to shine through it, and are capable of capturing objects that are greater than 1 micrometer in length. The fibers themselves are so small that they allow more air through than classical aerodynamics calls for because the size was now smaller than the average distance an air particle travels before a collision. This all stems from the manufacturing technique involving a broken down polymer of one charge being sprayed on one side while ethanol is sprayed with the opposite charge on the other. They then merge and form the film upon which the filter is made of (Roizen).
Humans often try to take the properties of nature as a starting point for inspiration. After all, it seems like nature has a lot of complicated systems operating rather smoothly. Researchers from the Department of Energy’s Pacific Northwest National Laboratory found a way to copy one of the most basic features nature has to offer: cell membranes. Often made of lipids, these membranes allow materials in and out of the cell according to their makeups yet retain their shape despite their miniscule size, but making an artificial one is difficult to do. The team was able to overcome these difficulties using a lipid-like material known as a peptoid, which mimics a lipids basic feature of a chain of molecules which has a fatty receptor at one end and a water receptor at the other. When the peptoid chains were out into a liquid, they began to arrange themselves into nanomembranes which have a high durability in many different solutions, temperatures, and acidities. How the membranes exactly form is still a mystery. Potential uses for the synthetic material include lower-energy water filtration as well as selective drug treatments (Beckman).
In a Similar Vein
This prior peptoid membrane isn’t the only new option on the market. Scientists from the University of Minnesota have found a way to use a “crystal growth process for making ultra-thin layers of material with molecular-sized pores,” otherwise known as zeolite nanosheets. Like the peptoids, these can filter on a molecular level with both the size of the object as well as its spatial properties. Because of the crystal nature of zeolites, it encourages a growth around any given seed into a lattice which makes for great applications (Zurn).
One of the world’s best fuel sources is hydrogen, but trying to extract it from the environment is challenging because of its bonding to other elements. Enter MXene, a nanomaterial developed by Drexel University that utilizes a thin gap inside the membrane to separate larger elements while allowing hydrogen to travel through it unimpeded, according to work from South China University of Technology and Drexel’s College of Engineering. The material has its porous nature carved out of it, allowing for selectivity in its channel which can be customized beyond just a physical barrier but also using its chemical properties as well, absorbing elements we don’t want as well (Faulstick).
A frequent dream of science fiction writers is smart wear that reacts to changes with our bodies. An early forefather of one of those suits has been developed by KJUS. Their ski jumpsuit actively pumps out sweat from the skin of the user, allowing them to modulate their temperature better and prevent risk of hypothermic effects. To accomplish this, membranes are located in the back of the suit with “an electrically conductive fabric,” and the membranes themselves have billions of small openings. With a minute electrical impulse, the holes act like pumps and pull the moisture away from the skin. The new suit can operate in extreme temperatures and also doesn’t diminish the breathability of the user. Pretty awesome! (Klose)
A New Way
Normally, small membranes are reinforced with atomic layer deposition, which involves manipulating vapors to condense and create a desired surface. Argonne National Laboratory has created a new method known as sequential infiltration synthesis which overcomes the major hurdle of the past, namely that the coating would restrict the openings present on the membrane because of the stacked layers. With the sequential method, we are changing the membrane itself from within, no longer losing our desired properties for the membrane. With polymer-based membranes, one can infuse it with inorganic substances that increase the rigidness of the material as well as the inertness of the substance (Kunz).
More surprises are to come in the future! Come back soon to see the latest updates to membrane technology.
Beckman, Mary. “Scientists create new thin material that mimics cell membranes.” Innvovations-report.com. innovations report, 20 Jul. 2016. Web. 13 May 2019.
Faulstick, Britt. “’Chemical net’ could be key to capturing pure hydrogen.” Innovations-report.com. innovations report, 30 Jan. 2018. Web. 13 May 2019.
Klose, Rainer. “Get rid of sweat at the push of a button.” Innovations-report.com. innovations report, 19 Nov. 2018. Web. 13 May 2019.
Kunz, Tona. “Barely scratching the surface: A new way to make robust membranes.” Innovations-report.com. innovations report, 13 Dec. 2018. Web. 14 May 2019.
Roizen, Valerii. “Physicists get a perfect material for air filters.” Innovations-report.com. innovations report, 02 Mar. 2016. Web. 10 May 2019.
Zurn, Rhonda. “Researchers develop groundbreaking process for creating ultra-selective desperation membranes.” Innvovations-report.com. innovations report, 20 Jul. 2016. Web. 13 May 2019.
© 2020 Leonard Kelley