Researchers have made an electronic skin patch that can monitor muscle movement, store the data it collects, and use stored data patterns to decide when to deliver medicine through the skin. The patch could be useful for monitoring and treating Parkinson’s disease and epilepsy, its creators say.

Wearable devices that continuously monitor physiological cues can help doctors understand and treat diseases such as epilepsy, heart failure, and Parkinson’s. A few research groups have been trying to develop discreet health monitoring devices based on flexible, stretchable electronics that can be plastered on the skin, heart or brain.

But the new system is the first that can store data and deliver drugs, says Dae-Hyeong Kim, a chemical and biological engineering professor at Seoul National University and one of the device’s creators. In the "closed-loop feedback system," says Kim, the stored data is used for statistical pattern analysis, which helps to track symptoms and drug response. "For more quantitative tracking of progression of symptoms and responses to medications, wearable healthcare devices that monitor important cues, store recorded data, and deliver feedback therapeutic agents via the human skin in a controlled way are highly required," he says.

Kim and his collaborators at the University of Texas at Austin and wearable health-monitoring device-makerMC10 integrated the sensors, memory, and drug-delivery components, all made of nanomaterials, onto a stretchable polymer substrate that is soft and flexible like human skin. They reported their design in the journal Nature Nanotechnology.

On the topside of the skin-like polymer patch, the research team printed three things: silicon nanomembrane strain sensor arrays; serpentine chromium-and-gold nanowires that act as both heaters and temperature sensors; and drug-loaded porous silica nanoparticles. The strain sensors detect motion such as Parkinson’s tremors. The heater controls the temperature of the polymer, which in turn controls the diffusion of the drugs into the skin (heat degrades the physical bonding between the nanoparticles and the drugs). The temperature sensors monitor skin temperature during drug delivery to prevent burns.

What’s most unique about the new electronic patch is the stretchable memory. Researchers have previously made resistive random access memory, an up-and-coming class of nonvolatile memory, using metal oxide nanomembranes. Those devices were stiff and brittle. Here, the researchers have made stretchable memory devices by sandwiching three layers of gold nanoparticles between ultra-thin titanium oxide nanomembranes printed on aluminum electrodes.

The memory device can be bent and twisted, it works when stretched to 125 percent of its original length, and works well even after 1000 stretching cycles.

As a simple demonstration, the researchers placed the wearable patch on the wrist. The motion sensors measured frequency of simulated tremors by sensing tension and compression of the muscle. The frequency was recorded and fed through a control circuit that recognizes characteristic patterns of Parkinson’s disease. This, in turn, triggered drug release.

Right now, the memory element requires a power supply and a data transmitter. The researchers say that they will need batteries or wireless power transmission and wireless communication in stretchable formats to make a truly wearable and wireless patch.

Photo: Donghee Son and Jongha Lee


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Restoring Hearing With Beams of Light

Gene therapy and optoelectronics could radically upgrade hearing for millions of people

13 min read
A computer graphic shows a gray structure that’s curled like a snail’s shell. A big purple line runs through it. Many clusters of smaller red lines are scattered throughout the curled structure.

Human hearing depends on the cochlea, a snail-shaped structure in the inner ear. A new kind of cochlear implant for people with disabling hearing loss would use beams of light to stimulate the cochlear nerve.

Lakshay Khurana and Daniel Keppeler

There’s a popular misconception that cochlear implants restore natural hearing. In fact, these marvels of engineering give people a new kind of “electric hearing” that they must learn how to use.

Natural hearing results from vibrations hitting tiny structures called hair cells within the cochlea in the inner ear. A cochlear implant bypasses the damaged or dysfunctional parts of the ear and uses electrodes to directly stimulate the cochlear nerve, which sends signals to the brain. When my hearing-impaired patients have their cochlear implants turned on for the first time, they often report that voices sound flat and robotic and that background noises blur together and drown out voices. Although users can have many sessions with technicians to “tune” and adjust their implants’ settings to make sounds more pleasant and helpful, there’s a limit to what can be achieved with today’s technology.

8 channels

64 channels

Since optogenetic therapies are just beginning to be tested in clinical trials, there’s still some uncertainty about how best to make the technique work in humans. We’re still thinking about how to get the viral vector to deliver the necessary genes to the correct neurons in the cochlea. The viral vector we’ve used in experiments thus far, an adeno-associated virus, is a harmless virus that has already been approved for use in several gene therapies, and we’re using some genetic tricks and local administration to target cochlear neurons specifically. We’ve already begun gathering data about the stability of the optogenetically altered cells and whether they’ll need repeated injections of the channelrhodopsin genes to stay responsive to light.

Our roadmap to clinical trials is very ambitious. We’re working now to finalize and freeze the design of the device, and we have ongoing preclinical studies in animals to check for phototoxicity and prove the efficacy of the basic idea. We aim to begin our first-in-human study in 2026, in which we’ll find the safest dose for the gene therapy. We hope to launch a large phase 3 clinical trial in 2028 to collect data that we’ll use in submitting the device for regulatory approval, which we could win in the early 2030s.

We foresee a future in which beams of light can bring rich soundscapes to people with profound hearing loss or deafness. We hope that the optical cochlear implant will enable them to pick out voices in a busy meeting, appreciate the subtleties of their favorite songs, and take in the full spectrum of sound—from trilling birdsongs to booming bass notes. We think this technology has the potential to illuminate their auditory worlds.

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