Levitating Water With Sound Improves Contaminate Detection

A journal published in optics letters 2018 has revealed the successful use of ultrasonic waves to levitate a water droplet for decontamination purposes. This will drastically reduce the reaction time necessary to treat pollution related water shortages on the front lines.

A mix of the sounds vibration (wobbling) and the evaporation process itself leads to a gyrating motion where heavy metals begin to aggregate at the center of the droplet.  This makes it easier for scientists to employ a measurement technique called laser induced breakdown spectro-graphy.

A method for transforming heavy metals in to plasma, the fourth state of matter by vaporizing the metal and displacing electrons via the extreme heat of laser Beams. This releases a particular spectra of light in the form of radiation which enables them to identify toxic elements in a fraction of the time for much less cost.

Research team leader Victor Contreras, from Instituto de Ciencias Físicas UNAM, Mexico.

“Despite the large variety of water sensors that offer continual monitoring, detection of multiple heavy metals dissolved in water can only be performed by sending samples off for specialized laboratory analysis,”

“Our new technique is one step toward the development of a simpler analysis approach that could be applied on-site and in real time. This type of water analysis could be used by agricultural, pharmaceutical, water purification and other industries to monitor water for contaminants.”

concentrations of heavy metals. For example, they detected 0.7 milligrams per liter of cadmium and 0.2 milligrams per liter of barium. They also showed that the acoustic levitation technique they used is stable enough for reproducible LIBS analysis.

they want to optimize the mechanical design of the acoustic trap to achieve more stable levitation conditions, which will improve the reproducibility of the LIBS readings. They also want to increase the sensitivity by stably levitating smaller drops, which further concentrates the contaminants. This is a key step toward miniaturizing the device because it will allow the use of less sensitive, but more compact detectors.

“Acoustic levitation is a simple and inexpensive method to preconcentrate the elements of interest while avoiding contamination from the substrate surface,” said Contreras. “Moreover, it does not require the sample to have any type of electric or magnetic response like some other methods used to achieve levitation.”

cover photo Jairo Peralta and Victor Contreras, Instituto de Ciencias Físicas UNAM

Optical Society Journals Optic Letters

can reliably detect very low levels of heavy metals like barium, cadmium and mercury within just a few minutes.

05/03/18 Levitating water droplets with sound waves to improve contaminant detection


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