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        Flexible device could treat

        hearing loss without batteries

              ome people are born with
              hearing loss, while others
        Sacquire it with age, infections
        or long-term noise exposures. In                                                    An electrically
        many instances, the tiny hairs in                                                   conductive
        the inner ear’s cochlea that allow                                                  membrane
        the brain to recognize electrical                                                   implanted inside
        pulses as sound are damaged. As                                                     a model ear
        a step toward an advanced artificial                                                simulates cochlear
        cochlea, researchers in ACS Nano                                                    hairs by converting
        report a conductive membrane,                                                       sound waves into
        which translated sound waves into                                                   electrical pulses;
        matching electrical signals when                                                    wiring connects
        implanted inside a model ear,                                                       the prototype to a
        without requiring external power.                                                   device that collects
                                                                                            the output current
                                                                                            signal. Credit:
        When the hair cells inside the
        inner ear stop working, there’s                                                     Adapted from
        no way to reverse the damage.                                                       ACS Nano 2021;
        Currently, treatment is limited to                                                  DOI: 10.1021/
        hearing aids or cochlear implants.                                                  acsnano.1c04242
        But these devices require external
        power sources and can have
        difficulty amplifying speech
        correctly so that it’s understood    barium titanate nanoparticles       say their self-powered device is
        by the user. One possible solution   coated with silicon dioxide into a   sensitive to the wide acoustic range
        is to simulate healthy cochlear      conductive polymer, which they      needed to hear most sounds and
        hairs, converting noise into the     dried into a thin, flexible film. Next,   voices.
        electrical signals processed by      they removed the silicon dioxide
        the brain as recognizable sounds.    shells with an alkaline solution.   The authors acknowledge
        To accomplish this, previous         This step left behind a sponge-like   funding from the General
        researchers have tried self-powered   membrane with spaces around        Program of the National
        piezoelectric materials, which       the nanoparticles, allowing them    Natural Science Foundation
        become charged when they’re          to jostle around when hit by sound   of China, the Fundamental
        compressed by the pressure           waves. In tests, the researchers    Research Funds for the Central
        that accompanies sound waves,        showed that contact between         Universities and the Double
        and triboelectric materials,         the nanoparticles and polymer       First-Class-Independent
        which produce friction and static    increased the membrane’s            Innovation-Subject Construction.
        electricity when moved by these      electrical output by 55% compared
        waves. However, the devices          to the pristine polymer. When       Story Source:
        aren’t easy to make and don’t        they sandwiched the membrane        Materials provided by American
        produce enough signal across the     between two thin metal grids, the   Chemical Society. Note: Content
        frequencies involved in human        acoustic sensing device produced    may be edited for style and length.
        speech. So, Yunming Wang and         a maximum electrical signal at 170
        colleagues wanted a simple way to    hertz, a frequency within the range   Journal Reference:
        fabricate a material that used both   of most adult’s voices. Finally, the   1. Jiaqi Zheng, Zhaohan Yu,
        compression and friction for an      researchers implanted the device    Yunming Wang, Yue Fu, Dan
        acoustic sensing device with high    inside a model ear and played       Chen, Huamin Zhou. Acoustic
        efficiency and sensitivity across a   a music file. They recorded the    Core–Shell Resonance Harvester
        broad range of audio frequencies.    electrical output and converted     for Application of Artificial Cochlea
                                             it into a new audio file, which     Based on the Piezo-Triboelectric
        To create a piezo-triboelectric      displayed a strong similarity to the   Effect. ACS Nano, 2021; DOI:
        material, the researchers mixed      original version. The researchers   10.1021/acsnano.1c04242

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