Physicists have created a “microphone” that captures the rustle of bacteria

microphone, bacteria
© Rhett S. Miller/UC Regents

Physicists from California have developed an ultra-sensitive pressure sensor that can sense and record the movements of bacteria, the internal beating of heart cells and other inaudible noises of the microcosm, according to an article published in the journal Nature Photonics.

“In fact, we have created a miniature analogue of an atomic force microscope, while having the sensitivity of optical” tongs “. We can not only “hear” these weakest sounds and “feel” these forces, but also accurately measure them. Now we have a tool to observe interactions and changes on scales as small as we’ve ever gotten,” said Donald Sirbuly of the University of California at San Diego, USA.

The device, created by Serbuli and his colleagues, is the thinnest nanowire, consisting of three components – tin oxide nanofibers and two types of gold nanoparticles, “glued” to their surface using electrostatic attraction forces and super-elastic polymer glue.

Nanoparticles and thin strips of certain metals, such as gold or silver, can absorb visible light and transmit it further as other forms of electromagnetic radiation. At this time, so-called plasmons appear on the surface of the metal – collective oscillations of electrons capable of absorbing and emitting energy in the form of light waves.

If a beam of light is passed through such a “sandwich”, then the nanofibers will begin to emit it, and plasmons will introduce a kind of “interference” into it. The way these interferences are arranged strongly depends on the distance between the plasmon source and the light guide. This distance, due to the high elasticity of the adhesive, will change noticeably if waves are passed through the light guide or a force is applied to it.

Thanks to this, the “microphone” of Serbuli and his colleagues can feel record-breaking low forces and acoustic vibrations – such a light guide can pick up sounds that are a thousand times weaker than those that a person can hear, and measure forces of the order of 160 femtonewtons (trillionths of a newton). In general, this gadget is about 10 times more sensitive than an atomic force microscope, and at the same time it is much easier to use.

Using this “nanomicrophone”, the scientists recorded the sounds that bacteria make when moving through a nutrient medium, and also measured the strength of vibrations produced by single muscle cells of the heart.

In the future, Serbuli notes, the brainchild of his group will be able to find single cells in solution and observe their migrations and behavior, as well as the movement of objects inside them. Such measurements, scientists hope, will make it easier to take photographs of individual microbes and to interpret the results of other biological and physical experiments.



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