TECHNOLOGY

Wireless power transfer by volume conduction

Wireless power transfer (WPT) methods are frequently used as an alternative to electrochemical batteries to energize electronic implants. However, methods based on inductive coupling or ultrasounds have obtained high miniaturization levels at the expense of link efficiency, penetration depth or functionality.

 

In the last years we have proposed and demonstrated a WPT method that avoids the use of bulky components within the implant, resulting in thin, flexible and elongated devices that can be deployed by injection. The implants are powered and controlled by applying — through external electrodes — high frequency current bursts that flow through the tissues by volume conduction6. The currents are picked-up by the implant’s electrodes (located at the ends of the elongated body) and are rectified for powering and bidirectional communications. This allows the integration of the electronics in an application-specific integrated circuit (ASIC).

Flexible and addressable intramuscular microstimulator developed during the eAXON project (J Neural Eng. 2022 Sep 14;19(5)).
Within the eAXON project, we developed tubular addressable microstimulators for neuroprosthetics. The implants include a hermetic capsule and an integrated circuit7 and resulted in an overall diameter of 0.97 mm. The devices were successfully tested in anesthetized rabbits and sheep.

We have validated in humans that high frequency current bursts complying with safety standards and applied through two textile electrodes strapped around a limb can provide substantial power from pairs of implanted electrodes, and are innocuous and imperceptible8. We have also validated in humans that this WPT method can be used to power and bidirectionally communicate with implantable devices that can perform electrical stimulation and EMG sensing9. 

Injectable device implanted in gastrocnemius muscle of healthy participant.

WPT based on volume conduction for RPM of heart failure patients

While developing our neuroprosthetics technology, we realized that the same novel WPT and communications method could also be used to develop minimally invasive implants capable of sensing relevant biomedical parameters for remote patient monitoring (RPM). Due to their enormous socioeconomic impact, we decided to explore the applicability of our envisioned sensing platform in cardiovascular diseases.

Our technology could revolutionize this field, as the microsensors: 

  • can fit in thinner blood vessels,
  • are easier and safer to implant,
  • can sense measure multiple biomedical parameters,
  • can work in a network of devices for multi-site sensing.

Our microsensing technology is protected by one granted patent (EP21382183.8) and one patent application (EP19382757.3). From its conception, it has been developed according to regulatory guidelines.

References

7 J Neural Eng. 2022 Sep 14;19(5). Link

8 IEEE Trans Biomed Eng. 2023 Feb;70(2):659-670. Link

9 J Neuroeng Rehabil. 2024 Jan 3;21(1):4. Link

This project has received funding from the European Union’s HORIZON-EIC-2023-TRANSITIONOPEN program under grant agreement No 101136633. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union and the Agency. Neither the European Union nor the granting authority can be held responsible for them.