Implanted generator could use ultrasound to charge pacemaker batteries
When a pacemaker's battery gets low, the whole implant typically has to be surgically replaced. Scientists are therefore developing a noninvasive battery recharging system, which utilizes externally applied ultrasound.
First of all, it should be acknowledged that there presently are other methods of wireless energy transfer.
Electromagnetic induction, for instance, is already used to charge the batteries of devices such as smartphones. It only works over a distance of about 1.5 cm (0.6 in), however, plus the heat generated during the charging process limits its use for safely charging devices within the body.
Magnetic resonance is another method, although the magnetic fields it utilizes may be subject to interference from other wireless communication frequencies like Bluetooth and Wi-Fi.
With these and other limitations in mind, a team from the Korea Institute of Science and Technology (KIST) has developed an implantable ultrasound-powered generator that could be integrated into a pacemaker or other implant. It utilizes what is known as the triboelectric effect, in which certain materials become electrically charged when they're rubbed against one another – it's what's responsible for the static charge that occurs when you're combing your hair.
In the case of this device, externally applied ultrasonic waves cause thin layers of triboelectric and ferroelectric materials to vibrate back and forth between two electrode layers. This generates an electrical current, which could be used to charge a battery.
When the setup was tested in the lab, it was possible to generate 8 milliwatts of charging power even when the generator and the emitter were both underwater and located 6 cm (2.4 in) apart – this was enough to simultaneously illuminate 200 LEDs, or transmit a Bluetooth signal underwater. In fact, the system could conceivably also be utilized in undersea technologies.
"This study demonstrated that electronic devices can be driven by wireless power charging via ultrasonic waves," said the lead scientist, Dr. Hyun-Cheol Song. "If the stability and efficiency of the device are further improved in the future, this technology can be applied to supply power wirelessly to implantable sensors or deep-sea sensors, in which replacing batteries is cumbersome."
A paper on the research was recently published in the journal Energy & Environmental Science.
Scientists at Saudi Arabia's King Abdullah University of Science and Technology have been working on an ultrasonic implant-charging system of their own, which incorporates a hydrogel that produces electricity when subjected to ultrasound. Other experimental methods of recharging pacemaker batteries without removing them include the use of light, heartbeats and body movements.