The eardrum, also called the tympanic membrane or myringa is a thin, cone-shaped membrane that plays a crucial role in sensing sound and transmitting the sound from the air to the ossicles. In the current microphone industry, a rigid diaphragm which consists of metal film or Si membrane is used to fulfill acoustic-electric transition. Although the diaphragm is able to respond to sound, the stiff and brittle configuration may limited its further application in vivo implantation. It is necessary to fabricate a bionic flexible eardrum which can respond and record sound with similar flexible mechanic properties, wide frequency response domain, high sensitivity and ultra-fast response time.
Recently, Professor Ting Zhang and his group from the Suzhou Institute of Nanotech and Nanobionics (SINANO), Chinese Academy of Sciences (CAS), developed an ultra-thin flexible electronic eardrum to detect sound signal by optimizing the chosen materials and micro-structure design of the device.
To realize the thin and elastic property, the polydimethylsiloxane (PDMS) was spin-coated on to the uniformly micro-structured Si mold on which sensing nanomaterials are deposited and co-curing with the ultra-violet treated polyethylene (PE) film. The flexible electronic eardrum (50 μm thick) can detect and record sound with high signal to noise ratio (~ 55 dB), fast response time (76.9 μs), and wide frequency response (20-13000 Hz) even after 150,000 times cycling pressure test. The sensors have a high degree of consistency with the original audio signal and can identify the sound of different people. The result has been published in the latest issue of Nano Research.
a, Image of the flexible electronic eardrum placed in an ear model. The inset figure shows the image of the bended electronic eardrum. b, Schematic configuration of the electronic eardrum. c, The band-pass filtered electronic eardrum signal was compared with original sound wave and iPhone5 signal. d, A picture showing the voice recognition experiment. The electronic eardrum was suspended by clamps in front of the participant to detect his voice and the signal was recorded by oscilloscope.
a, The Double-layer electronic eardrum with/without micro pattern (in red and orange, respectively) and single PE-PDMS film (green) based device were tested under the same sound. b, The frequency response of the electronic eardrum with different side length of pyramid structure 10 (in red), 25 (in blue) and 50 (in green) μm. c and d, The sensitivity of the electronic eardrum changes with different strain states and thickness of the PDMS layers respectivly.
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