Laser-induced graphene (LIG) is a spongy version of graphene that was developed three years ago in the Rice University lab of chemist James Tour. To create LIG, a sheet of polyimide sheet is burnt partway through with a laser, which turns the surface into a lattice of interconnected graphene sheets.
The researchers have since suggested uses for the material in wearable electronics and fuel cells and for superhydrophobic or superhydrophilic surfaces.
According to their report in the American Chemical Society's ACS Applied Materials and Interfaces, LIG also protects surfaces from biofouling, the buildup of microorganisms, plants or other biological material on wet surfaces.
"This form of graphene is extremely resistant to biofilm formation, which has promise for places like water-treatment plants, oil-drilling operations, hospitals and ocean applications like underwater pipes that are sensitive to fouling," Tour said in a statement. "The antibacterial qualities when electricity is applied is a great additional benefit."
Tests on LIG without the charge confirmed that graphene-based nanoparticles have antibacterial properties. When 1.1 to 2.5 volts were applied, the highly conductive LIG electrodes "greatly enhanced" those properties.
Under the microscope, the researchers watched as fluorescently tagged Pseudomonas aeruginosa bacteria in a solution with LIG electrodes above 1.1 volts were drawn toward the anode. Above 1.5 volts, the cells began to disappear and vanished completely within 30 seconds. At 2.5 volts, bacteria disappeared almost completely from the surface after one second.
The Rice lab partnered with Prof. Christopher Arnusch, a lecturer at the Ben-Gurion University of the Negev’s Zuckerberg Institute for Water Research, who specialises in water purification. Arnusch's lab tested LIG electrodes in a bacteria-laden solution with 10 per cent secondary treated wastewater and found that after nine hours at 2.5 volts, 99.9 per cent of the bacteria were killed and the electrodes strongly resisted biofilm formation.
The researchers suspect bacteria may meet their demise through a combination of contact with the rough surface of LIG, the electrical charge and toxicity from localised production of hydrogen peroxide. LIG's anti-fouling properties keep dead bacteria from accumulating on the surface, Tour said.
"The combination of passive biofouling inhibition and active voltage-induced microbial removal will likely make this a highly sought-after material for inhibiting the growth of troublesome natural fouling that plagues many industries," Tour said.