Researchers exploring the use of ultrasonic sound to power implanted devices

22-04-2022 |   |  By Robin Mitchell

Researchers from Korea are exploring the use of h2sound to power implanted devices inside the human body. What challenges do medical implants present, what did the researchers demonstrate, and is this a viable option for powering implanted devices?


What challenges do medical implants face?


With the many advances in medical science, electronics, and computing technology, one would expect medical implants to be a common thing, yet their use is extremely limited. One typical example of a medical implant is the pacemaker which helps to provide consistent electrical pulses to the heart. Another common implant found in pets is RFID tags which can be used to identify key details, including current owner, address, and telephone number. While RFIDs are rare in people, they are becoming increasingly popular with their ability to act as identifiers for payment processing, security access, and even medical information such as allergies.

When designing an implanted sensor, numerous challenges must be addressed, and the biggest by far is that the resulting device must be biologically inert. A biologically inert device will not trigger a reaction from the immune system when implanted, meaning it will be ignored. A device that is not biologically inert will cause the immune system to form pus around the device, and this can lead to severe consequences, including septicaemia and death.

Another major challenge with implanted devices is finding a source of reliable power. While batteries and clever energy minimisation technologies can be used for long-life operation, only some battery technologies are safe for use inside the human body. When the battery does run out, it requires an operation to remove the device and/or battery. Wireless power can be transmitted through radio waves, but the body is mostly water, which hinders implanted devices' ability to receive practical amounts of energy.


Researchers use h2waves to transfer energy to implanted devices


Recently, researchers from the Korean Institute of Science and Technology have demonstrated a method of wireless energy transfer using h2sound waves and triboelectric generators. Simply put, the researchers attached triboelectric generators that generate electricity when under mechanical vibration to a dummy load (LED array) and then powered the triboelectric generators from a substantial distance of 6cm using an h2generator.

The first experiment reported by the researchers shows the device functioning when submerged in a tank of water with a distance of 6cm between the h2source and the receiving device. This experiment also demonstrated the use of a dummy load of 200 LEDs and a wireless sensor to show sensor readings, all using the power from h2waves. The second experiment then implanted the receiver into pork flesh with multiple layers, including skin, fat, and muscle. Even with a distance of around 6cm, the device could still receive energy and power.

However, the researchers also developed an improvement to the triboelectric generator to improve its ability to absorb incoming h2waves. On its own, the triboelectric generator has an efficiency of around 1%, but the combination of a ferromagnetic layer increases this to more than 4%. The overall energy received by the generator was around 8mW, and while this may not be significantly high, it is enough to drive energy harvesters and small devices.


Is this a viable option for implanted devices?


There is no doubt that h2energy can deliver enough power to an implanted circuit, as the researchers from KIST demonstrated, but is the use of h2waves viable in the human body?

To power devices in the body, a user would have to have an h2energy source mounted onto the surface of their skin. Such a device could be rechargeable which removes the need to change batteries, and the wireless nature of energy delivery to the internal device makes management very simple. But a wearable h2power source could be bulky and extremely inconvenient to wear, which would make such a power option unsuitable for many.

However, there is one area of concern that could see h2energy systems being entirely scrapped: their long-term effect on human tissue and bone. Depending on the amount of energy being delivered by an h2transmitter, h2energy can cause internal tissue to heat up while also causing skin irritation. Furthermore, it is believed that h2energy can potentially cause microfractures in bone, but this may only be an issue for extremely high energies (those involved with cleaning).

So, is the use of h2energy to power implanted devices a viable option? While more research and development is needed, it does seem that this could be a practical method for powering devices inside the body without needing to replace batteries.


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By Robin Mitchell

Robin Mitchell is an electronic engineer who has been involved in electronics since the age of 13. After completing a BEng at the University of Warwick, Robin moved into the field of online content creation developing articles, news pieces, and projects aimed at professionals and makers alike. Currently, Robin runs a small electronics business, MitchElectronics, which produces educational kits and resources.

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