Graphene Dialysis Membranes

One application's material defect is another's path to functionality. This is true of graphene, when taken beyond the realm of electronics and applied within the field of diffusion filtration. A new graphene dialysis membrane, being developed by MIT's Department of Engineering, harnesses the formation of pores in pristine graphene material for selective separation and advanced filtration of nanometer-sized molecules. 

Improving Process Times

"State-of-the-art dialysis membranes comprise a relatively thick polymer layer with tortuous pores, and suffer from low rates of diffusion leading to extremely long process times (often several days) and poor selectivity" (1)

 

Rather than slowly making their way through a 20 nm or thicker complex network of filtering cavities, specific molecules can diffuse through the less than 1 nm thick graphene membrane up to ten times faster. This new graphene technology has the potential to expedite processes for blood purification (hemodialysis), molecule isolation for medical diagnosis, as well as to remove residue from solutions in pharmaceutical production.

Chemical Vapor Disposition

The membrane is created using chemical vapor deposition of the graphene onto a copper foil. The copper is removed by an etching process, and the graphene is then transferred to a perforated polycarbonate substrate that acts as a supporting scaffold. The polycarbonate perforations accommodate the selected molecule size to increase the effectiveness of their passage as they are diffused through the graphene membrane.

“What’s exciting is, what’s not great for the electronics field is actually perfect in this [membrane dialysis] field,” Kidambi says. “In electronics, you want to minimize defects. Here you want to make defects of the right size. It goes to show the end use of the technology dictates what you want in the technology. That’s the key.”

MIT NEWS

The MIT researchers have developed a fine-tuning process in which they take advantage of the elimination reaction between an oxygen radical and carbon which leaves holes in the graphene as the carbon is ejected. By adjusting the length of time that the graphene is exposed to oxygen plasma, they are able to control the size and density of the pores created. This allows for a specific determination of pore size to create a highly customized, ultra-thin, selective-separation membrane. 

“We are incredibly excited to release our new brand Boyd Biomedical. This is an important step for us as we continue our growth in the medical device and life sciences markets. We’re looking forward to many more successful years commercializing breakthrough innovations under our new brand platform.”

KIDAMBI

Filtering Efficiency of Diffusion Membranes

In the research lab, the team tested several membranes with pore sizes ranging from 0.66 to 4 nanometers. They were successful in selectively filtering molecules of potassium chloride, vitamin B12, and lysomzyme. When results were compared to the effectiveness of current commercial diffusion membranes, they found that, though the usable surface area was small, the graphene membrane far outperformed current technology in filtering efficiency.

Graphene & Medical Device Applications

The potential application of graphene, as an innovative material that's tougher than steel while still being flexible and stretchable, is still being explored across all industries. With its superconductive characteristics and ability to convert any wavelength of light into a current, this ultra-thin layer of hexagonally arranged carbon has been assumed to be best suited to the electronics industry. While it has the drawbacks of being a delicate material that is difficult to handle and expensive to make, the researchers at MIT have proven that looking beyond assumption might be the best strategy for putting graphene into practical use. 

Conclusion

With their graphene dialysis membrane showing such excellent performance in comparison to current state-of-the-art selective filtering, the MIT researchers may have just laid the groundwork for the next era of membrane technology.

Given that graphene becomes standardized and the cost of production decreases respectively, this material could have a positive, if unexpected, effect on the medical and pharmaceutical industries. Improving the lives of people who endure lengthy hemodialysis treatments, cleaner and safer pharmaceuticals, and quicker, more accurate diagnosis technology; with advances such as MIT's graphene dialysis membrane, these are things we can look forward to in our future.

REFERENCES

Sources:(1)P. R. Kidambi, D. Jang, J.-C. Idrobo, M. S. H. Boutilier, L. Wang, J. Kong, R. Karnik, Adv. Mater. 2017, 1700277. https://doi.org/10.1002/adma.201700277