If microorganisms were having a conversation, we certainly couldn't hear it, until perhaps now. German physicists developed the world's first "nano-ear", which they claim can be used to listen to microorganisms as well as tiny machines.
According to the Institute of Physics website, Physics World, the ear was created by "optically trapping" a gold nanoparticle. What this means is a highly focused laser holds the particle, like a tweezer, in its beam. This technique, Physics World reports, has long been useful for observing small specimens because it doesn't damage them, but it has now exhibited properties that show it is sensitive to sound as well.
According to Physics World, Jochen Feldmann and Andrey Lutich at the Ludwig-Maximilians University in Munich, along with a team of researchers, have seen that the particle can be moved in the beam by vibrations from sound waves -- even the smallest ones. By measuring the movement of the particle, researchers can "listen" to the vibrations being made.
Physics World has more on the methodology:
The team's set-up consisted of two sound sources placed in a water-based medium. The first "loud" source is a tungsten needle glued on a loudspeaker that vibrates at a frequency of 300 Hz. The second, weaker source is made up of bunches of gold nanoparticles that are periodically heated by a second laser to create sound waves at a frequency of 20 Hz. The nano-ear is a 60 [nanometer] nm gold nanoparticle trapped in a 808 nm wavelength laser beam.
When either of the sound sources is turned on, the ensuing vibrations cause the trapped particle to move in the same direction as the propagating sound waves.
[Alexander] Ohlinger and colleagues used a video camera to track the motion of the trapped particle. They then tested how sensitive their nano-ear was by analysing the recorded trajectories of the particle.
The research found that the nano-ear can "hear" sounds at six orders of magnitude lower than that of humans. The team will be using the technology to try and listen to bacteria and viruses. Ohlinger said the technology could emerge as a new type of "acoustic microscopy", giving organisms a new form of identification based on their sound.
[H/T Popular Science]