A team of researchers from the College of Agriculture and Life Sciences at Cornell University suggests that using a bubble bath with a constant acoustic sound in the water to wash produce might offer a chemical-free, gentle approach for cleaning agricultural produce, medical instruments and semiconductors.

Currently, agricultural produce is washed with bubblers for greens or soft brushes for root crops for cleaning off sediments. Further, chlorine, ozone and peroxyacetic acid are typically added to the water as sanitizers.

Source: Cornell University

As a chemical free alternative, this new approach has researchers placing vegetables in a bath with a bubbler. Once immersed, the team added a constant acoustic drone at a low frequency using an underwater speaker. According to the team, the sound produces resonance in bubbles, causing them to vibrate. When washed with these resonating bubbles, vegetables were 90% cleaner than vegetables washed with bubbles but without any sound waves or at frequencies that didn't lead to resonance.

"There are few options for cleaning soft surfaces," the researchers noted. "It might be one of the best ways to clean a soft surface without using metal, plastic or solid brushes.”

Such an alternative cleaning method could potentially be refined to help farmers and households avoid harsh chemicals and eliminate surface damage to vegetables and fruits, while simultaneously reducing the high amounts of energy often expended with traditional cleaning.

In addition to using vibrating bubbles to scrub surfaces, the team also discovered that different bubble sizes resonate at specific frequencies, and tuning these frequencies produces a stop-and-go motion that enhances cleaning. In the lab, this approach removed protein-based residue from surfaces.

The team suggests that thanks to its gentle, non-abrasive nature, the approach could also prove promising for delicate objects like semiconductors and medical tools.

An article detailing the approach, “Acoustic‐driven surface cleaning with millimeter‐sized bubbles at translational resonance,” appears in the journal Droplet.