Sound waves propagate through the air by creating a series of high pressure and low pressure areas. An array of transducers can be used to c...
Sound waves propagate through the air by creating a series of high pressure and low pressure areas. An array of transducers can be used to control the high and low pressure areas, using ultrasonic sound waves, which are beyond the hearing range of humans. However, any bats in the area would be disturbed by the noise. By controlling the alternating high pressure and low pressure areas, objects can be trapped, or levitated. Such devices can be made at home, using cheap components that can be purchased from a hardware store. Using tornadoes of sound to suspend objects is only a recent development, and was first demonstrated in 2018 by researchers from the University of Bristol. As the suspended particles had limited maneuverability, researchers developed a holographic acoustic elements framework, which allowed these bands of high pressure and low pressure areas to be shaped into various types of instruments. Although invisible and inaudible, these are tweezers, twisters and containers made up of pure sound, that can be used to manipulate objects just the same as the more conventional counterparts. Now, the approach is being used for actual science. In a new research paper, Caltech scientist Jack Beauchamp and his colleagues described the use of acoustic levitation to study the chemistry of skin cancer drugs. It was the first study of chemical reactions in a suspended, well less reactor. Beauchamp refers to the approach as “lab-in-a-drop”. A 1 millimeter water droplet was coated with lipids, the molecules that make up cell membranes. When introduced to the suspended water droplet, the lipids rose to the surface to form a thin film, or membrane around the drop, similar to how they would behave in a cell. The drug, known as Temoporfin was then introduced to the suspended droplet. When excited with a red laser light, Temoporfin destroys the molecules it comes in contact with, including the lipids that form the cell membranes. The resulting chemical reactions were studied using a mass spectrometer. In potential skin cancer treatments, a laser light can be shone on the affected areas after introducing the drug, to selectively eliminate the cancerous tissue. “When you're doing this chemistry, you'd like to be able to carry out these reactions under conditions where you don't have any contact of the liquid with surfaces. We achieve this goal by performing chemistry in a levitated droplet,” Beauchamp explains. The technique can be used for other kinds of studies as well, as almost any object of a small size can be suspended using the technique, including living insects. The removal of any containers means that previously complicated apparatus can be simplified. Other potential applications involve production lines where contact with the components is minimised. The approach can theoretically be scaled up to levitate humans or even bigger objects. Acoustic levitation is a low cost technique and can be used in innovative ways in a lab environment. An acoustic levitator similar to the one used by Beauchamp can be created by using off the shelf electronic components and 3D printing, for as little as Rs 5,000.
Source: Caltech
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