Researchers are developing tiny 3D printed microphones inspired by insect ears that can accurately determine the direction of a sound. Currently, bulky and energy-intensive equipment is required for sound directionality, but insect ears possess a thin tissue called the tympanum, similar to the human eardrum, which converts sound waves into nerve signals.
Despite their small size, insects can achieve impressive hearing feats that surpass the capabilities of larger devices. For example, the vehicle-mounted Boomerang system from Raytheon, used to determine the direction of a gunshot, relies on a microphone array that is approximately half a meter wide. In contrast, the nocturnal moth Achroia grisella can also detect the direction of sounds, accomplishing this feat with just a tympanum measuring about half a millimeter in width. It is believed that the moth developed this skill to detect predatory bats and ultrasonic mating calls.
By studying insect structures, scientists attempted to replicate them using silicon microelectromechanical systems (MEMS), but these devices lacked the flexibility and 3D structural variations of real insect ears.
To overcome this, researchers from the University of Strathclyde turned to 3D printing to mimic insect ears more accurately. They used flexible hydrogel membranes with piezoelectric materials and made them porous to enhance performance. The microscopic variations in thickness, porosity, density, and pliability allowed the synthetic membranes to function as sensitive and efficient acoustic sensors.
These insect-inspired microphones could have applications in energy-efficient sound detection and cochlear implants, offering faster signal detection and reduced delays. Further research is needed to fully understand how insect ears achieve their remarkable hearing abilities and to optimize the design of these miniature microphones.
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