Scientists use sound waves to remove microplastics from waterways

The novel solution – which was presented in March at a meeting of the American Chemical Society – might not be what you’d expect, however.

Using sound, or what they’re referring to as a bulk acoustic wave system, scientists at Shinshu University have been experimenting with a surprisingly basic form of tech to purify water.

Unlike previous ultrasound filtering techniques, this exciting new development can theoretically remove both large and small microplastic particles using a unique two-step process.

First, high-pitched sound waves push them into a central channel.

When applied inside of a confined area, such as a steel tube, the ultrasonic frequency concentrates particles in a certain perimeter.

From there, they can be collected, or filtered out, as microplastic-free water fills the branches of the main central path of the device.

‘Our proposed microfluidic device, which is designed based on a hydraulic-electric analogy, has three 1.5 mm-wide microchannels connected via four serial 0.7-mm-wide trifurcated junctions,’ explains Professor Yoshitake Akiyama of the Department of Mechanical Engineering and Robotics at the Faculty of Textile Science and Technology.

‘The MPs are aligned at the centre of the middle microchannel using a bulk acoustic wave of 500-kHz resonance frequency. As a result, a 3.2-fold enrichment of MPs must occur at each junction, resulting in a 105-fold overall enrichment in the device.’

Akiyama’s hope is that his method will eventually be installed in washing machines, factories, and other sources of microplastics to prevent further discharge of these particles to the planet.