Porous Cellulose Thin Films as Sustainable and Effective Antimicrobial Surface Coatings

Abstract: In the present work, we developed an effective antimicrobial surface film based on sustainable micro-fibrillated cellulose (MFC). The resulting porous cellulose thin film is barely noticeable to human eyes due to its sub-micron thickness, of which the surface coverage, porosity and microstructure can be modulated by the formulations and coating process.

Using goniometers and a quartz crystal microbalance (QCM), we observed a threefold reduction in water contact angles and accelerated water evaporation kinetics on the cellulose film (more than 50% faster than that on a flat glass surface). The porous cellulose film exhibits a rapid inactivation effect against SARS-CoV-2 in 5 minutes, following deposition of virus loaded droplets, and an exceptional ability to reduce contact transfer of liquid, e.g. respiratory droplets, to surfaces such as artificial skin by 90% less than that from a planar glass substrate. It also shows excellent antimicrobial performance in inhibiting the growth of both gram-negative and gram-positive bacteria (E.coli and S.epidermidis) due to the intrinsic porosity and hydrophilicity. Additionally, the cellulose film shows nearly 100% resistance to scraping in dry condition due to its strong affinity to the supporting substrate, whilst good removability once wetted with water, suggesting its practical suitability for daily use.

Importantly, the coating can be formed on solid substrates readily by spraying, which requires solely a simple formulation of a plant-based cellulose material with no chemical additives, rendering it a scalable, affordable, and green solution as antimicrobial surfaces. Implementing such cellulose films could thus play a significant role in controlling future pan- and epidemics, in particularly during the initial phase when suitable medical intervention needs to be developed and deployed.