Consider the multitude of surfaces encountered daily, ranging from kitchen countertops and public transport handrails to workplace desks and personal phone screens.
These common contact points serve as conduits for the facile transmission of a variety of pathogenic viruses and other microorganisms.
The prevalent mechanism of infection typically involves direct contact with a contaminated surface, followed by inadvertent touching of the eyes, nasal passages, or oral cavity.
While chemical disinfectants are conventionally employed for surface sanitization, their efficacy can be transient. Furthermore, these agents may pose environmental risks and contribute to the emergence of antimicrobial resistance, a phenomenon where pathogens develop immunity to therapeutic interventions due to recurrent exposure.
In a recent investigation, detailed in our publication in Advanced Science, my collaborators and I have engineered a novel, thin polymeric film endowed with microscopic topographical features. These nanoscale imprints, measured in billionths of a meter, are designed to emulate the naturally occurring nanotexture of insect wings. This unique surface architecture possesses the inherent capability to physically disrupt viral structures, including the human parainfluenza virus type 3 (hPIV-3).
This innovative material presents an economically viable and readily scalable solution for rendering surfaces, such as those found on mobile devices and medical apparatus, significantly less conducive to disease transmission.
Existing methodologies for mitigating the airborne spread of viruses via contact surfaces primarily rely on physical cleaning to eliminate detritus and disinfection to eradicate unseen pathogens.
For effective germ eradication, disinfectants necessitate a period of sustained contact in a wet state. Achieving this condition can prove challenging in diverse real-world environments.
Moreover, surfaces are subject to rapid recontamination through subsequent human interaction. The application of disinfectants often involves potent chemical agents, which carry the potential to compromise equipment integrity and adversely affect environmental ecosystems.
Researchers have previously explored strategies for imparting antiviral properties to surfaces. These approaches typically involve integrating specific constituents like graphene, tannic acid, or other biologically derived compounds into personal protective equipment, encompassing items such as masks, gloves, eyewear, headgear, and respiratory devices.
While these surface treatments demonstrate considerable efficacy, they may also introduce risks to human well-being. Additionally, concerns exist regarding their environmental impact due to potential chemical leaching, and their effectiveness can diminish over time as the potency of the active agents wanes.
Our trajectory towards developing a surface capable of physically destroying viruses commenced over a decade ago.
Initially, our objective was to fabricate a surface with exceptional smoothness, anticipating that microbes would be unable to adhere and would simply slide off. Counterintuitively, our findings revealed the opposite: bacterial adhesion proved relatively facile on nanoscopically smooth substrates.
Nature provides compelling examples of surfaces that resist bacterial colonization. Consider the hydrophobic wings of cicadas and dragonflies. While these wings exhibit self-cleaning properties, their mechanism of action is less about repellent forces and more akin to functioning as intrinsic antimicrobial agents.
In other words, they possess the capacity to eliminate bacteria.
Intrinsic antimicrobial agents are naturally derived substances capable of eradicating microbes, rather than merely impeding their proliferation.
Experimental investigations conducted by myself and my colleagues, utilizing wings coated with gold, substantiated that this bacterial eradication capability is attributable not to chemical properties of the surface, but rather to its physical topography.
The nanostructural elements present on the surface effectively induce mechanical stress on bacterial cell membranes, leading to their expansion and subsequent rupture.
Prior research from our group demonstrated that silicon substrates patterned with nanoscale spikes could efficiently neutralize viruses upon contact. However, the inherent rigidity of silicon limited its applicability to intricately shaped objects.
In the present study, we addressed this constraint by developing a virus-disrupting material that is both lightweight, cost-effective, and possesses flexible characteristics.
This material comprises a slender acrylic film densely populated with countless ultra-fine pillars. Although these nanotextured elements appear smooth to the touch, the integrated nanopillars are engineered to engage and stretch the outer envelope of a virus until it is compromised. This process results in viral inactivation through the application of physical forces.
In vitro examinations utilizing hPIV 3, a pathogen responsible for respiratory ailments like bronchiolitis and pneumonia, revealed that up to 94% of viral particles were mechanically disintegrated or irreparably damaged within an hour of exposure to this material.
Our findings indicate that the proximity of the nanopillars, rather than their vertical dimension, is the paramount factor influencing efficacy. Optimal performance was observed with densely packed pillars spaced approximately 60 nanometers apart.
The fabrication mold employed in the creation of this material can be readily scaled, paving the way for extensive industrial applications. These span diverse sectors, including food packaging, public transportation infrastructure, healthcare facilities, and office environments.
Nanostructured surfaces are inherently designed for resilience. Nevertheless, they remain susceptible to the same physical, chemical, and environmental degradation factors that affect conventional materials, exhibiting a finite lifespan.
The quest for surfaces that are impervious to microbial contamination continues to yield new insights. However, these nanotextured surfaces represent a significant advancement, offering substantial promise in the global effort to combat viral propagation and providing a compelling alternative to established chemical-based methodologies.
