Bubble-capturing surface helps get rid of foam — ScienceDaily
In many industrial processes, reminiscent of in bioreactors that produce fuels or prescription drugs, foam can get in the way in which. Frothy bubbles can take up rather a lot of house, limiting the amount obtainable for making the product and typically gumming up pipes and valves or damaging residing cells. Companies spend an estimated $three billion a yr on chemical components referred to as defoamers, however these can have an effect on the purity of the product and should require additional processing steps for his or her removing.
Now, researchers at MIT have provide you with a easy, cheap, and fully passive system for decreasing or eliminating the foam buildup, utilizing bubble-attracting sheets of specifically textured mesh that make bubbles collapse as quick as they type. The new course of is described within the journal Advanced Materials Interfaces, in a paper by current graduate Leonid Rapoport PhD ’18, visiting pupil Theo Emmerich, and professor of mechanical engineering Kripa Varanasi.
The new system makes use of surfaces the researchers name “aerophilic,” which magnetize and shed bubbles of air or fuel in a lot the identical means that hydrophilic (water-attracting) surfaces trigger droplets of water to cling to a surface, unfold out, and fall away, Varanasi explains.
“Foams are everywhere” in industrial processes, he says, together with beer brewing, paper making, oil and fuel manufacturing and processing, biofuel technology, shampoo and cosmetics manufacturing, and chemical processing.
Also, “It’s one of the main challenges in cell culture or in bioreactors,” he provides. To promote cell development, varied gases are sometimes subtle by means of the water or different liquid medium. But this may result in a buildup of foam, and because the tiny bubbles burst they will produce shear forces that may harm or kill the cells, so controlling the foam is crucial.
The regular means of coping with the foam downside is by including chemical compounds reminiscent of glycols or alcohols, which generally then should be filtered out once more. But that provides value and further processing steps, and might have an effect on the chemistry of the product. So, the workforce requested, “How can you get rid of foams without having to add chemicals? That was our challenge,” Varanasi says.
To deal with the issue, they created high-speed video in an effort to research how bubbles react after they strike a surface. They discovered that the bubbles are inclined to bounce away like a rubber ball, bouncing a number of instances earlier than finally sticking in place, simply as droplets of liquid do after they hit a surface, solely the wrong way up. (The bubbles are rising, so that they bounce downward.)
“In order to effectively capture the impacting bubble, we had to understand how the liquid film separating it from the surface drains,” says Rapoport. “And we had to start at square one because there wasn’t even an established metric to measure how good a surface is at capturing impacting bubbles. Ultimately, we were able to understand the physics behind what causes a bubble to bounce away, and that understanding drove the design process.”
The workforce got here up with a flat gadget that has a set of rigorously designed surface textures at a spread of dimension scales. The surface was tuned in order that bubbles would adhere immediately with out bouncing, and shortly unfold out and dissipate to make means for the following bubble as a substitute of accumulating as foam.
“The key to quickly capturing bubbles and controlling foam turned out to be a three-layered system with features of progressively finer sizes,” says Emmerich. These options assist to lure a really skinny layer of air alongside the surface of a fabric. This surface, generally known as a plastron, is analogous to the feel of some feathers on diving birds that assist hold the animals dry underwater. In this case, the plastron helps to make the bubbles stick with the surface and dissipate.
The web impact is to scale back the time it takes for a bubble to stay to the surface by a hundredfold, Varanasi says. In exams, the bouncing time was diminished from a whole bunch of milliseconds to just some milliseconds.
To take a look at the thought within the lab, the workforce constructed a tool containing a bubble-capturing surface and inserted it right into a beaker that had bubbles rising by means of it. They positioned that beaker subsequent to an similar one containing foaming suds with a sheet of the identical dimension, however with out the textured materials. In the beaker with the bubble-capturing surface, the foam shortly dissipated all the way down to nearly nothing, whereas a full layer of foam stayed in place within the different beaker.
Such bubble-capturing surfaces might simply be retrofitted to many industrial processing services that presently depend on defoaming chemical compounds, Varanasi says. He speculated that within the longer run, such a way would possibly even be used as a approach to seize methane seeping from melting permafrost because the world warms. This might each forestall some of that potent greenhouse fuel from making it into the ambiance, and on the similar time present a supply of gasoline. At this level that chance is “pie in the sky,” he says, however in precept it might work.
Unlike many new expertise developments, this method is easy sufficient that it could possibly be readily applied, Varanasi says. “It’s ready to go. … We look forward to working with industry.”
The work was supported by the Bill and Melinda Gates Foundation.