Beams of Light Restore Hearing

A team of researchers affiliated with multiple institutions in Germany has developed a cochlear implant that converts sound waves to light signals instead of electrical signals. In their paper published in the journal Science Translational Medicine, the group describes their new hearing aid and how well it worked in test rats.

Cochlear implants work by converting  into  that are sent to nerve cells in the ear. The idea is to bypass damaged hair cells inside the cochlea to restore hearing. But because the fluid in the ear also conducts electricity, the electrical signals that are generated can cross, leading to a loss of resolution. The result is difficulty hearing in some situations, such as crowded rooms, or when listening to music with a lot of instruments. In this new effort, the researchers sought to replace the electrical signals in such devices with , which would not be muddied by the fluid in the ear, and thereby improve hearing.

In all types of cochlear devices, sound entering the ear is directed to a computer chip that processes the sound it detects. After processing, the chip directs another device to create signals that are sent to the neurons. With the new device, the researchers developed a device that would generate light using LED chips and send it through fiber cable directly to the nerve cells.

In order for such a system to work, the nerve cells inside the ear would have to be modified in some way to allow them to respond to light instead of electricity. For testing purposes, the researchers genetically modified lab rats to grow  in their  that would respond to light. In their device, they used an implant with 10 LED chips. They also trained the rats to respond to different sounds before disabling their hair cells and implanting the cochlear devices. The implants worked as hoped, as the rats were able to respond in similar ways to the same generated sounds.

The researchers suggest that in people, such a device would use 64 LED or other light source channels. They also plan to conduct more research with the device and hope to start clinical trials by 2025.


Acoustic Fabric

Having trouble hearing? Just turn up your shirt. That’s the idea behind a new “acoustic fabric” developed by engineers at MIT and collaborators at Rhode Island School of DesignThe team has designed a fabric that works like a microphone, converting sound first into mechanical vibrations, then into electrical signals, similarly to how our ears hearAll fabrics vibrate in response to audible sounds, though these vibrations are on the scale of nanometers — far too small to ordinarily be sensed. To capture these imperceptible signals, the researchers created a flexible fiber that, when woven into a fabric, bends with the fabric like seaweed on the ocean’s surface.

The fiber is designed from a “piezoelectric” material that produces an electrical signal when bent or mechanically deformed, providing a means for the fabric to convert sound vibrations into electrical signalsThe fabric can capture sounds ranging in decibel from a quiet library to heavy road traffic, and determine the precise direction of sudden sounds like handclaps. When woven into a shirt’s lining, the fabric can detect a wearer’s subtle heartbeat features. The fibers can also be made to generate sound, such as a recording of spoken words, that another fabric can detectA study detailing the team’s design appears in Nature. Lead author Wei Yan, who helped develop the fiber as an MIT postdoc, sees many uses for fabrics that hear.

Wearing an acoustic garment, you might talk through it to answer phone calls and communicate with others,” says Yan, who is now an assistant professor at the Nanyang Technological University in Singapore. “In addition, this fabric can imperceptibly interface with the human skin, enabling wearers to monitor their heart and respiratory condition in a comfortable, continuous, real-time, and long-term manner.”

Yan’s co-authors include Grace Noel, Gabriel Loke, Tural Khudiyev, Juliette Marion, Juliana Cherston, Atharva Sahasrabudhe, Joao Wilbert, Irmandy Wicaksono, and professors John Joannopoulos and Yoel Fink at MIT, along with collaborators from the Rhode Island School of Design (RISD), Lei Zhu from Case Western Reserve University, Chu Ma from the University of Wisconsin at Madison, and Reed Hoyt of the U.S. Army Research Institute of Environmental Medicine.


Flexible device could treat hearing loss without batteries

Some people are born with hearing loss, while others acquire it with age, infections or long-term noise exposures. In many instances, the tiny hairs in the inner ear’s cochlea that allow the brain to recognize electrical pulses as sound are damaged. As a step toward an advanced artificial cochlea, researchers in ACS Nano report a conductive membrane, which translated sound waves into matching electrical signals when implanted inside a model ear, without requiring external power.

An electrically conductive membrane implanted inside a model ear simulates cochlear hairs by converting sound waves into electrical pulses; wiring connects the prototype to a device that collects the output current signal.

When the hair cells inside the inner ear stop working, there’s no way to reverse the damage. Currently, treatment is limited to hearing aids or cochlear implants. But these devices require external power sources and can have difficulty amplifying speech correctly so that it’s understood by the user. One possible solution is to simulate healthy cochlear hairs, converting noise into the electrical signals processed by the brain as recognizable sounds. To accomplish this, previous researchers have tried self-powered piezoelectric materials, which become charged when they’re compressed by the pressure that accompanies sound waves, and triboelectric materials, which produce friction and static electricity when moved by these waves. However, the devices aren’t easy to make and don’t produce enough signal across the frequencies involved in human speech. So, Yunming Wang and colleagues from the University of Wuhan wanted a simple way to fabricate a material that used both compression and friction for an acoustic sensing device with high efficiency and sensitivity across a broad range of audio frequencies.

To create a piezo-triboelectric material, the researchers mixed barium titanate nanoparticles coated with silicon dioxide into a conductive polymer, which they dried into a thin, flexible film. Next, they removed the silicon dioxide shells with an alkaline solution. This step left behind a sponge-like membrane with spaces around the nanoparticles, allowing them to jostle around when hit by sound waves. In tests, the researchers showed that contact between the nanoparticles and polymer increased the membrane’s electrical output by 55% compared to the pristine polymer. When they sandwiched the membrane between two thin metal grids, the acoustic sensing device produced a maximum electrical signal at 170 hertz, a frequency within the range of most adult’s voices. Finally, the researchers implanted the device inside a model ear and played a music file. They recorded the electrical output and converted it into a new audio file, which displayed a strong similarity to the original version. The researchers say their self-powered device is sensitive to the wide acoustic range needed to hear most sounds and voices.


How to Copy and Paste a Brain

Samsung and Harvard University have published new research that suggests it is possible to develop a brain-inspired memory chip.

In a perspective paper published in Nature Electronics, the researchers from the partnering organisations proposed that the brain’s neuronal connection map could be copied using nanoelectrode array. They specified that the nanoelectrode array could be used to record the electrical signals produced by the large number of neurons found in the brain. The recordings could then be used to inform the neuronal map by indicating where neurons connect with one another and how strong the connections are, the researchers claimed.

Once copied, the neuronal map could then be pasted onto a high-density three-dimensional network of solid-state memory, such as commercial flash memory used in solid-state drives or resistive RAM.

Ultimately, the memory chip would contain traits of the brain, such as low power, facile learning, adaption to environment, autonomy, and cognition, the researchers said. The paper also suggests one possible way to speed up pasting the neuronal map is by directly downloading the map onto a memory chip.

The vision we present is highly ambitious,” Samsung Advanced Institute of Technology fellow Donhee Ham. “But working toward such a heroic goal will push the boundaries of machine intelligence, neuroscience, and semiconductor technology.”

Looking ahead, Samsung plans to continue its research into neuromorphic engineering as part of its development of AI semiconductors.