Powering Electronic Implants by High Frequency Volume Conduction: In Human Validation

Minguillón, Jesús; Tudela-Pi, Marc; Becerra-Fajardo, Laura; Perera-Bel, Enric; del-Ama, Antonio J.; Gil-Agudo, Ángel; Megía-García, Álvaro; García-Moreno, Aracelys; Ivorra, Antoni

doi:10.1109/tbme.2022.3200409

Cited by 7 publications

(9 citation statements)

References 68 publications

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“…As previously demonstrated in [30,[41][42][43], volume conduction can be electrically modeled using a twoport impedance network that characterizes coupling between the external system and the implanted device. Here, such modeling approach was tried for further confirmation of its validity.…”

Section: In Vivo Study 221 System Modelingmentioning

confidence: 99%

“…Here, as in [30], the electrode impedances were neglected considering they are low compared to tissue impedances. Tissue impedances were approximated as resistances, which were calculated by imposing voltages and currents across the external and the implant electrodes in simulations.…”

Section: In Vivo Study 221 System Modelingmentioning

confidence: 99%

“…The function generator (AFG 3022B by Tektronix Inc.) uses the signal produced by the digital controller to modulate a 3 MHz sinusoidal voltage carrier performing amplitude-shift keying modulation (on-off keying). The modulated waveform (of the sort displayed in figure 4(b) top) is then amplified using a custom-made high voltage amplifier [30] and delivered across the tissue through two external electrodes. For the in vivo demonstration, the external electrodes consisted of 1.5 cm wide bands made from silver-based stretchable conductive fabric (Shieldex® Technik-tex P130 + B by Statex Produktions und Vertriebs GmbH) strapped around the target limb of the animal.…”

Section: External Generatormentioning

confidence: 99%

“…The SAR indicates the heat dissipated per unit of tissue mass and is calculated averaging over 10 g of mass and 6 min. Previous studies have demonstrated, numerically [54] and in humans [30], that it is possible to transfer powers in the order of milliwatts to implanted devices via volume conduction of HF current bursts that comply with these safety standards.…”

Section: Electrical Safetymentioning

confidence: 99%

“…Compared to other WPT methods, galvanic coupling and capacitive coupling offer the advantage of not integrating bulky parts, such as piezoelectric crystals or coils, within the implant for receiving the energy transferred by the remote transmitter. As demonstrated in [30], the energy can be readily picked up with a pair of thin electrodes separated by a few millimeters or centimeters.…”

Section: Introductionmentioning

confidence: 99%

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Wireless networks of injectable microelectronic stimulators based on rectification of volume conducted high frequency currents

et al. 2022

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Objective. To develop and in vivo demonstrate threadlike wireless implantable neuromuscular microstimulators that are digitally addressable. Approach. These devices perform, through its two electrodes, electronic rectification of innocuous high frequency current bursts delivered by volume conduction via epidermal textile electrodes. By avoiding the need of large components to obtain electrical energy, this approach allows the development of thin devices that can be intramuscularly implanted by minimally invasive procedures such as injection. For compliance with electrical safety standards, this approach requires a minimum distance, in the order of millimeters or a very few centimeters, between the implant electrodes. Additionally, the devices must cause minimal mechanical damage to tissues, avoid dislocation and be adequate for long-term implantation. Considering these requirements, the implants were conceived as tubular and flexible devices with two electrodes at opposite ends and, at the middle section, a hermetic metallic capsule housing the electronics. Main results. The developed implants have a submillimetric diameter (0.97 mm diameter, 35 mm length) and consist of a microcircuit, which contains a single custom-developed integrated circuit, housed within a titanium capsule (0.7 mm diameter, 6.5 mm length), and two platinum-iridium coils that form two electrodes (3 mm length) located at opposite ends of a silicone body. These neuromuscular stimulators are addressable, allowing to establish a network of microstimulators that can be controlled independently. Their operation was demonstrated in an acute study by injecting a few of them in the hind limb of anesthetized rabbits and inducing controlled and independent contractions. Significance. These results show the feasibility of manufacturing threadlike wireless addressable neuromuscular stimulators by using fabrication techniques and materials well established for chronic electronic implants. Although long-term operation still must be demonstrated, the obtained results pave the way to the clinical development of advanced motor neuroprostheses formed by dense networks of such wireless devices.

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Section: In Vivo Study 221 System Modelingmentioning

confidence: 99%

Section: In Vivo Study 221 System Modelingmentioning

confidence: 99%

Section: External Generatormentioning

confidence: 99%

Section: Electrical Safetymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Wireless networks of injectable microelectronic stimulators based on rectification of volume conducted high frequency currents

et al. 2022

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First-in-human demonstration of floating EMG sensors and stimulators wirelessly powered and operated by volume conduction

Becerra-Fajardo,

Minguillon,

Krob

et al. 2023

Preprint

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Background: Very recently we reported the design and evaluation of floating semi-implantable devices that receive power from and bidirectionally communicate with an external system using coupling by volume conduction. The proposed approach, of which the semi-implantable devices are proof-of-concept prototypes, may overcome some of the limitations presented by existing neuroprostheses, especially those related to the size of the implantable devices and the need to perform complex surgical procedures. This is accomplished as the implants do not require rigid and bulky components within them and can be developed as flexible threadlike devices, a form factor that is beneficial for motor neuroprostheses. Here we report the first-in-human demonstration of these semi-implantable devices for both electromyography (EMG) sensing and electrical stimulation in an acute study. Methods: A single floating device, consisting of implantable thin-film electrodes and a non implantable miniature electronic circuit connected to them, was deployed in the upper or lower limb of six healthy participants. Two external textile electrodes were strapped around the limb and were connected to the external system, which delivered high frequency current bursts. Within these bursts, 13 different commands were modulated to communicate with the wireless implant. In one participant, isometric forces were measured while acquiring EMG activity of voluntary muscle contractions using the semi-implantable device. Results: The floating EMG sensors and stimulators were successfully deployed in the biceps brachii and the gastrocnemius medialis muscles, and the external system was able to power them and bidirectionally communicate with them. Both sensing and stimulation parameters were configured externally using the communication protocol developed for the system. In one participant, both electrical stimulation and EMG acquisition assays were successfully performed, demonstrating the feasibility of the approach to power and communicate with the floating devices. Conclusions: This is the first time that floating EMG sensors and electrical stimulators that are powered and communicate by volume conduction are demonstrated in humans. These devices, which can be highly miniaturized using current microelectronic technologies, open the possibility of using coupling by volume conduction in networked neuroprosthetics, obtaining fully implantable wireless devices with sensing and stimulation capabilities.

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Networks of Injectable Microdevices Powered and Digitally Linked by Volume Conduction for Neuroprosthetics: a Proof-of-Concept

Becerra-Fajardo

Minguillón

Comerma-Montells

et al. 2023

2023 11th International IEEE/EMBS Conference on Neural Engineering (NER)

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Wireless power transfer (WPT) methods such as inductive coupling and ultrasounds are used as an alternative to electrochemical batteries to energize active implantable medical devices. However, existing WPT methods require the use of bulky components (e.g., coils) that hinder miniaturization. To avoid this, we proposed the use of volume conduction of high frequency (HF) current bursts to power and bidirectionally communicate with threadlike implants that can be used for electrical stimulation and sensing (e.g., electromyography acquisition). Here, we in vitro demonstrate that several wireless devices can be powered and digitally linked by volume conduction. Eleven devices were randomly placed in a saline medium and were enclosed by two electrodes connected to an external system. The system interrogated the devices, and the waveforms obtained by the external system's demodulator were digitally processed to decode the information sent by the devices through the same HF current bursts. Data was successfully decoded from the devices, independently of the power that each single device obtained. The WPT efficiency of volume conduction boosts when a massive number of devices are powered with a single external system, creating a network of microdevices for neuroprosthetics. This will allow to accomplish closed-loop control for neural interphases using highly miniaturized injectable devices.

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Powering Electronic Implants by High Frequency Volume Conduction: In Human Validation

Cited by 7 publications

References 68 publications

Wireless networks of injectable microelectronic stimulators based on rectification of volume conducted high frequency currents

Wireless networks of injectable microelectronic stimulators based on rectification of volume conducted high frequency currents

First-in-human demonstration of floating EMG sensors and stimulators wirelessly powered and operated by volume conduction

Networks of Injectable Microdevices Powered and Digitally Linked by Volume Conduction for Neuroprosthetics: a Proof-of-Concept

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