The amazing biology of insects is a result of millions of years of evolutionary development. One of these structures is the ear of the lesser wax-moth (Achroia grisellaThese moths use ultrasonic mating sounds to attract bats that hunt them. These mating calls can attract bats, which then hunt the moths. This has led to them developing directional hearing so that they can detect not only potential mates, but also bat calling sounds.
What’s most astounding about this is that these moths that only live about a week as an adult can perform auditory feats that we generally require an entire microphone array for, along with a lot of audio processing. These moths’ tympanum, or eardrum is the key to their ability to do these feats. Instead of a flat, taut surface, as in mammals, this moth’s eardrum has intricate 3D structures and pores that appear to do much of their directional processing. This is what researchers, including a group of researchers from the University of Strathclyde have been trying for some time to replicate.
Researchers used a flexible, hydrogel with a piezoelectric substance that converted the acoustic signals into electrical signals. These were then connected to electrical tracks. This is then printed with 3D features, which are mixed with methanol, which forms droplets in the curing resin before being expelled, leaving the desired holes. One limitation is that currently used printers have a limited resolution of about 200 micrometers, which doesn’t cover the full features of the insect’s tympanum.
This could be used to reduce the size of audio processing in everything from cochlear devices to other applications.
(Heading Image: Mapping of displacement of a smaller wax moth (Achroia grimella) tympanum. (Credit: Andrew Reid) )