An antibacterial material mimicking the diamond-like pattern of shark skin may take a bite out of the rising incidence of bacterial infections. The multifunctional surface developed at the University of Massachusetts reduces microbial attachment and inactivates attached microorganisms.
The key is the addition of antibacterial and photocatalytic titanium dioxide nanoparticles to the shark skin material. Researchers printed surfaces with polymer and ceramic composites and then added the nanoparticles. The ceramic shark-skin-patterned surfaces were fabricated on a poly(ethylene terephthalate) substrate and were quickly cured, requiring only 10 seconds of near infrared irradiation.
When titanium dioxide nanoparticles are exposed to ultraviolet (UV) light, chemical reactions with water and hydroxide molecules form reactive hydroxyl radicals and superoxide ions that rupture the outer membranes of bacteria on contact and lead to cell death. The nanoparticles are low-cost, widely available and can be incorporated into transparent coatings, unlike more commonly known antimicrobials such as silver and copper. These advantages make titanium dioxide an attractive candidate for use in high-touch antimicrobial surface coatings.
Tests showed that shark skin surfaces without nanoparticles reduced the attachment of Escherichia coli by 70 percent compared to smooth films. Shark skin surfaces with titanium dioxide nanoparticles exposed to UV light for one hour killed off over 95 percent of E. coli and 80 percent of Staphylococcus aureus.
The surface properties of the nanoimprinted lithography materials can be tuned for different applications and environments, from soft and pliable polymers to extremely hard and wear-resistant ceramics. The fabrication method can be scaled up for mass production of high-performance coatings that repel and inactivate bacteria.