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Scientists use sound waves to remove microplastics from waterways

The surprisingly basic technology was developed by a team of researchers who believe it could offer a novel solution to the ever-increasing environmental and health threat posed by these tiny particles.

Microplastic pollution is a huge problem.

The tiny particles, which are undetectable to the human eye and less than 5 mm in length, have been wreaking havoc on our health and the environment’s for decades now.

Adding insult to injury, the waste they generate is also incredibly difficult to clean.

Yet the gravity of this issue wasn’t recognised until 2004, when a landmark study documented the presence of this type of debris across 17 different beaches.

In the years since, as you likely know, they’ve turned up everywhere: in soil, in the oceans, and even in our bloodstreams – the latter prompting WHO to declare them an area of concern and a potential emergency later down the line.

This is because 30 million metric tonnes of plastic (which takes over 1000 years to degrade) are dumped on land annually, almost 50 million metric tonnes are burned, and another 11 million are washed away by the sea.

The SeaCleaners | Microplastics in human blood and lungs: an urgent case for scientific research.

By 2040, these figures could be 77 million, 133 million, and 29 million respectively. Scary stuff, eh?

Fortunately, scientists have been scrambling to figure out how to rid the Earth of at least some of these minuscule polymer shards for as long as they’ve been making a mess.

Most recently, a team of researchers has made a promising first step towards waterways untainted by the remains of that carrier bag you threw out months ago.

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.