Measurements made with an ultrafast-laser-generated optical frequency comb are helping to explain for the first time how a new sterilization technique inactivates bacteria without the use of liquid chemicals or high temperatures. What's exciting about the work is that it will "help optimize solutions for the medical clinic where multi-drug-resistant bacteria are a growing problem," according to Marek Golkowski, assistant professor of electrical engineering and bioengineering at the University of Colorado Denver and lead author on a paper describing the work.1
Analysis of the sterilization approach is being done by JILA, an institute operated jointly by the university and by National Institute of Standards and Technology (NIST; Gaithersburg, MD). The sterilization instrument was designed to deliver an air stream of free radicals to quickly kill bacteria up to 3 m away. The researchers used a frequency comb system to measure the concentrations of reactive molecules in the airstream-ozone, hydrogen peroxide, nitrous oxide, and nitrogen dioxide. The comb identifies specific molecules in gases based on which colors of light, or comb "teeth," are absorbed by the gas, and in what amounts.
The comb system's capability to measure hydrogen peroxide is critical, because its presence and concentration is key to effective sterilization. But crucially, the comb technique also captures complex chemical reactions in the sterilization system in real time. According to the researchers, "The multiple and simultaneous reactions make numerical modeling of the chemical dynamics difficult, hence the need for direct measurement of simultaneous concentrations, a capability that the frequency comb spectroscopy uniquely provides."
1. M. Golkowski et al., IEEE Transact. Plasma Sci., PP, 99, 1–8 (2012).
