It is the COVID-19 pandemic that has awakened the consciousness of microbial spreading in public areas, especially workplaces and eateries. It is also anticipated by public health experts that it could take up to two to three years to finally stop COVID-19.
The Movement Control Order (MCO) was introduced to flatten the infection curve and SOPs have also been introduced by the government. Business operators are required to disinfect public areas, especially the touch surfaces (or frequent-contact surfaces), every few hours to prevent the growth of germs and minimise indirect contact spread.
The growth of microbes on these touch areas is facilitated by the uneven surface and pores at microscopic level whereby these microbes can hide inside the pores and nutrients can be gained from external organic agents, i.e. humans, insects, animals, etc.
The virus can also be transmitted when a person touches the contaminated surfaces, other than direct contact. Once the fingers have been in contact with virus particles, they can contaminate up to seven other clean surfaces, according to a group of UK researchers.
Naturally, the main idea to suppress the transmission of diseases and further reduce the chance of subsequent infection by these contaminated touch surfaces is to eliminate microbes on these touch surfaces and suppress them by creating a hostile environment towards microbe growth.
One of the methods to achieve this is to encourage the use of antimicrobial materials. However, the term antimicrobial (against microbes/microorganisms) refers to a general term that can be divided into three subgroups (i) antiviral (against virus i.e. influenza virus), (ii) antibacterial (against bacteria i.e. E. Coli) and (iii) antifungal (against fungi i.e. yeast and mold). An antimicrobial material can be a combination of any or all three functions mentioned above and be made into the following:
(i) Soft materials
Silver and copper are classified as soft materials because they are malleable. Silverware is well known for use as kitchenware and containers due to its antibacterial active agents i.e. the silver ions (Ag+). The silver ions have been shown to kill the bacteria by reacting with thiol groups in enzymes. But the mechanism for the copper ions is uncertain and it could be due to excessive oxidation level towards the cell induced by the copper ions (Cu2+), copper binding to non-copper required protein or copper induced membrane breakdown.
Studies showed the infectivity of Influenza A virus on stainless steel and copper surfaces, respectively, after a certain time of exposure (picture above). The green dot represents the virus that has been highlighted with fluorescence and scientists had successfully shown that Influenza A virus is weakened effectively on a copper surface compared to stainless steel surface which demonstrates the effectiveness of the use of copper surface. On the other hand, these materials are expensive and not suitable for large-scale application.
(ii) Hard materials
The hard materials are normally smooth and have no void for bacteria to permeate. Thus, it is hard for the bacteria to accumulate at these voids and the growth of these bacteria is suppressed.
One example of hard materials is Cristalite. It is harder than granites and has good scratch resistance that further reduces chance of scratch marks on surfaces which are prone to bacteria growth. And the non-porous surface can inhibit bacteria growth without the use of chemicals.
However, these hard materials are heavy and have limited applications i.e. table-top, benches and other large flat surfaces. While Cristalite is considered as ceramic material, copper alloys like brass, bronze, etc. can also be used as antimicrobial surface for table-top finishing.
(iii) Coating and films
Most coating and films are normally polymer incorporated with silver and copper nanoparticles with the aforementioned effects. Other than these two, zinc nanoparticles are also commonly incorporated into the coating for its antifungal properties. Coatings and films with these active ingredients can provide broad spectrum protection including virus, fungi and bacteria.
The major benefits of coating and films include low cost and they can be applied on almost any product surface with any shape. Many research groups have been focusing on the development of these coating and films by not only incorporating the silver and copper nanoparticles into the polymer carrier but also overcoming the weakness of polymer carrier against UV.
To date, the coat can last even up to a few years after thorough research and development. However, such coatings are not 100% scratch-proof and can be peeled off after a certain time, depending on the environment. Therefore, a recoating treatment is required to maintain the integrity of the protection which in turn is another cost.
Each category has its own pros and cons. Therefore, the selection of materials should depend on the purpose and condition of usage. Also, the depth of the pocket of the owner is another concern. However, this does not mean that scheduled cleaning and disinfection can be compromised. But the frequency can be reduced.
The use of antimicrobial materials, especially on touch surface like tables and chairs at the eateries, can help suppress the growth of germs and bacteria during the intervals of cleanings, prevent subsequent contamination and minimise the risk of disease spreading in public areas.
With the emerging need to combat and defeat COVID-19 in a short duration and reduce future COVID-19-like outbreaks, the use of antimicrobial material should be considered as the choice of materials, especially at schools, care facilities, public transport and workplaces, to further strengthen the public health system and multi-level barrier protection should be created at these places with high touch and high traffic surfaces.
Tan Kwee Yong, PhD, is an experienced lecturer at AUSMAT, Sunway College, KL. He is also a material scientist, registered graduate technologist and a member of standards technical panel for a US based certification body.