Nitrogen-Doped Graphene Face Masks for COVID-19

Parnika Saxena Thomas Jefferson High School for Science and Technology

This article was originally included in the 2021 print publication of the Teknos Science Journal.

More than 500,000 people have lost their lives to COVID-19 in the U.S alone. The media has been flooded with opposing views on how to deal with the virus. Virginia Governor Ralph Northam has mandated the use of masks. Doctors complained about the cumbersome N95 masks. Some people protested that masks stripped them of their identity. Keeping these perspectives in mind, I asked myself, “what if a clear, paper-thin mask existed that was effective enough by the government’s health standards, comfortable enough for healthcare workers, and transparent enough for the public to retain their identity?” By collaborating with professors at Carnegie Mellon University, I aim to develop this mask using graphene. 

Imagine a piece of pencil lead, made of graphite. One atomically thin layer of graphite is called graphene, which is an allotrope of carbon that has a hexagonal lattice structure. Bilayer graphene can have a diamond-like structure if pressure induced [3]. On its own, graphene is impermeable such that a helium atom cannot pass through a sheet of it. However, once graphene undergoes the chemical process of nitrogen doping, some carbon bonds in the graphene break, creating nanoscopic pores on the surface of the graphene. These nanopores are theoretically small enough to block COVID-19 particles yet large enough to let oxygen and carbon dioxide through, allowing nitrogen-doped graphene to serve as a COVID-19 filter through which we can breathe. Given that graphene is transparent and lightweight, masks that utilize this material would have greater public appeal and increase the effectiveness of masks, thus slowing the transmission of the virus and spreading out the number of patients that hospitals must tend to.

Researchers have found laser-induced graphene to be capable of acting as an effective air filter. Graphene also has a high surface area and thermal stability, allowing for it to sustain the high temperatures used to destroy microorganisms on its surface. Researchers at Rice University demonstrated a self-cleaning air filter using laser-induced graphene, a porous conductive graphene foam created using the photothermal conversion of a polyimide film by a CO2 laser cutter. The laser-induced graphene was proven to capture particles and bacteria. Utilizing a repeated Joule-heating mechanism, the filter surpassed 300°C. The high temperature kills the remaining microorganisms along with other molecules that may trigger negative biological reactions [5]. 

Besides air filters, graphene can also be used for water desalination. First, a graphene oxide nanosheet and polymer are created together on a porous ceramic substrate, which then undergo reduction and carbonization [2]. Additionally, being able to control the pore size of the membrane is powerful; in this study by Chen et al., the pores in the graphene membrane were sized to prevent the entry of salt [2]. For my mask, I am looking to create pores that are greater than 1 nanometer to allow for the passing of oxygen and carbon dioxide molecules, and smaller than 70 nanometers, to block the passing of COVID-19 particles. 

A crucial step in the mask production process is the transfer of graphene onto a porous substrate. A research study by Guio et al. found a method for transferring block copolymer thin films onto porous substrates in a precisely controlled manner that avoids the creation of macroscale defect structures such as cracks, tears, and wrinkles in the transfer. A 3D-printed transfer tool and drain chamber system to deposit the block copolymer thin films onto the porous substrate to be used as a water filtration membrane device [4]. Optical inspection and image analysis confirmed the success in avoiding macroscale defect structures using this mechanized process as opposed to the manual process of transferring graphene onto a substrate by hand. Graphene’s strength per unit weight is extremely high; however, at the macroscale, one layer of graphene still rips easily. A thin tissue paper is a fit analogy for understanding graphene’s strength and tendency to tear (S. B. Darling, personal communication, Feb. 2, 2021). Using a 3D-printed transfer tool and drain chamber system in my COVID-19 graphene mask production process gives me an alternative approach to prototyping the mask to ensure that the graphene mask is created without wrinkles and tears.

The research findings from the self-cleaning air filter, which consisted of laser-induced graphene, the graphene oxide membrane for water desalination, and the transferral method of graphene onto a porous substrate, informed how I approach my mask prototyping process. My original idea was to use nitrogen-doped graphene in face masks, but due to limited resources in that area, I decided to prototype the mask using graphene oxide alongside professors from Carnegie Mellon University. Thus far, the process of chemical vapor deposition has been used to transfer the graphene oxide flakes onto porous cellulose fibers. This mask prototype’s filtration efficiency and permeability of graphene oxide on cellulose fibers will be tested using the TSI Automated Mask Tester. Pressure differential is another variable that we will be testing for to ensure that enough oxygen and carbon dioxide can be inhaled and exhaled when wearing masks enhanced by graphene. 

While graphene masks seem to offer a lightweight, transparent, and more effective alternative to the current surgical and N95 masks, further research must be pursued before it can be mass-produced. As researchers, we must draw concepts from previous research to propose novel ideas that address pertinent health issues; my project applies concepts from graphene in air and water filters towards creating an idea for graphene COVID-19 masks. Researchers at MIT have also brought graphene back into the physics research scene after they found that stacking and twisting two sheets of graphene at a certain angle can result in the production of a superconductor, which allows electrons to flow with minimal resistance [1]. The future is bright if more resources can be directed towards social innovation based on promising materials like graphene. 

References

[1] Chang, K. (2019, October 30). A Physics Magic Trick: Take 2 Sheets of Carbon and Twist. The New York Times. https://www.nytimes.com/2019/10/30/science/graphene-physics-superconductor.html

[2] Chen, X., Zhu, Y.-B., Yu, H., Liu, J. Z., Easton, C. D., Wang, Z., Hu, Y., Xie, Z., Wu, H.-A., Zhang, X., Li, D., & Wang, H. (2021). Ultrafast water evaporation through graphene membranes with subnanometer pores for desalination. Journal of Membrane Science, 621, 118934. https://doi.org/10.1016/j.memsci.2020.118934 

[3] Geng, P., & Branicio, P. S. (2021). Atomistic insights on the pressure-induced multi-layer graphene to diamond-like structure transformation. Carbon, 175, 243-253. https://doi.org/10.1016/j.carbon.2021.01.007

[4] Guio, L., Liu, C., Boures, D., Getty, P. T., Waldman, R., Liu, X., & Darling, S. B. (2019). Procedure for the Transfer of Polymer Films Onto Porous Substrates with Minimized Defects. Journal of Visualized Experiments, (148). https://dx.doi.org/10.3791/59554

[5] Stanford, M. G., Li, J. T., Chen, Y., McHugh, E. A., Liopo, A., Xiao, H., & Tour, J. M. (2019). Self-Sterilizing Laser-Induced Graphene Bacterial Air Filter. ACS Nano, 13(10), 11912-11920. https://doi.org/10.1021/acsnano.9b05983