New Levitation Technique Allows 'Touchless' Chemical Reactions

The levitating droplets technique could help advance the fields of planetary science and medicinal chemistry, amongst others.
Chris Young

When we think of levitation, most of us think of magic tricks and movies. In the lab, however, research is being carried out on methods of levitation that allow droplets of liquid to be suspended in midair, allowing for contact-free experiments without containers or handling that might affect the outcome.

A team has just reported in a paper published, in the American Chemical Society's journal Analytical Chemistry, that they have developed a method that can do just that.


Magic, or science?

Though researchers have long been trying to develop a levitation method for experiments, mixing the droplets and observing their reactions has been challenging. The team that has just revealed the findings of their research, claims to allow researchers to use this potentially groundbreaking method in a laboratory, a press release explains.

Scientists had previously made devices that allowed them to levitate small objects, but most of these methods required the object to be levitated to have certain physical properties, such as electric charge or magnetism.

Acoustic levitation, which uses sound waves to suspend an object in a gas, doesn't rely on such properties. The problem is that existing for acoustic levitation and mixing of single particles or droplets has been prohibitively complex, and it has been difficult to take measurements of reactions using these devices.

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Contactless control of levitated droplets

In order to find a solution, scientists Stephen Brotton and Ralf Kaiser set out to develop a versatile technique for the contactless control of two chemically distinct droplets, using a set of probes to follow the reaction as the droplets merge.

The team created an acoustic levitator and suspended two droplets in it, one above the other. They then made the upper droplet oscillate by varying the amplitude of the sound wave. Using this method, they were able to make the oscillating upper droplet merge with the lower droplet at the same time as monitoring the resulting chemical reaction with infrared, Raman, and ultraviolet-visible spectroscopies.

The researchers tested their technique by combining different droplets. In one of these experiments, they merged an ionic liquid with nitric acid, causing a tiny explosion.

The new levitation method could allow scientists to study many different chemical reactions that weren't previously possible, with wide-ranging implications for fields like medicinal chemistry and planetary science, the researchers say.

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