A technology that scrubs and decontaminates medical instruments using only cold water and ultrasonic bubbles holds potential as a low-cost, eco-friendly cleaning alternative for healthcare providers.

Currently prototyped as a hand-held portable device, StarStream generates a stream of cold water at 2.1 L/min from a 10mm-diameter circular nozzle through which an ultrasonic field is projected. The device creates bubble clouds that clean surfaces without the need for detergents or chemicals.

StarStream's portability opens opportunities to clean items that cannot be decontaminated using ultrasonic cleaning tanks or baths. Image credit: Ultrawave. Invented and patented by Professor Tim Leighton and Dr. Peter Birkin of the University of Southampton, the technology works by propagating ultrasound energy (sound waves) through a low-pressure flow of cold water. The effect causes ripples in the walls of microscopic bubbles in the water. This in turn generates high shearing forces in the liquid close to the bubbles’ wall. This shear causes the bubbles to become abrasive, scouring the surfaces they encounter and cleaning them.

The ultrasonic bubbles are especially effective at getting into hard-to-reach crevices to completely remove soil and bacteria, the developers say. Recent tests found that StarStream is 1,000 times more effective than water alone in decontaminating the microorganism Pseudomonas aeruginosa, a major cause of hospital-acquired infections, they say.

For the healthcare sector, StarStream’s technology has the potential to speed up and improve the current three-stage decontamination process of gross soil removal, disinfection and sterilization.

According to Ultrawave—the company commercializing StarStream—the technology produces up to 97% energy savings compared to commercial cleaning methods. By operating without the use of detergent, run-off pollution of groundwater and streams is negated and the task of turning the used water back into safe drinking water is simplified.

StarStream is also portable, opening possible opportunities to clean items that cannot currently be decontaminated using ultrasonic cleaning tanks or baths.

The technology continues to undergo testing—by the Network for Anti-Microbial Resistance and Infection Prevention (NAMRIP)—founded by Leighton earlier this year in part with an investment from the Engineering and Physical Sciences Research Council and the Medical Research Council. NAMRIP has carried out successful tests of the technology in joint replacements, cleaning bones before transplant, and in cleaning surgical instruments for brain tissue decontamination.