Volume conduction energy transfer for implantable devices

Aiming at miniaturization, wireless power transfer (WPT) is frequently used in biomedical electronic implants as an alternative to batteries. However, WPT methods in use still require integrating bulky parts within the receiver, thus hindering the development of devices implantable by minimally invasive procedures, particularly when powers above 1 mW are required in deep locations. In this regard, WPT based on volume conduction of high frequency currents is an advantageous alternative relatively unexplored, and never demonstrated in humans. We describe an experimental study in which ac and dc electric powers in the order of milliwatts are obtained from pairs of needle electrodes (diameter = 0.4 mm, separation = 30 mm) inserted into the arms or lower legs of five healthy participants while innocuous and imperceptible high frequency (6.78 MHz) currents are delivered through two textile electrodes strapped around the considered limb. In addition, we demonstrate a procedure to model WPT based on volume conduction which characterizes coupling between the transmitters and the receivers by means of two-port impedance models which are generated from participants' medical images.

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Power Transfer by Volume Conduction: In Vitro Validated Analytical Models Predict DC Powers Above 1 mW in Injectable Implants

Tudela-Pi

¹

,

Becerra-Fajardo

²

,

García-Moreno

³

et al. 2020

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Galvanic coupling, or more precisely volume conduction, has been recently studied by different research groups as a method for intrabody communications. However, only in a very few occasions its use for powering implants has been proposed and proper analyses of such capability are still lacking. We present the development and the in vitro validation of a set of analytical expressions able to estimate the maximum ac and dc powers attainable in elongated implants powered by volume conduction. In particular, the expressions do not describe the complete power transfer channel but the behavior of the implants when the presence of an electric field is assumed. The expressions and the in vitro models indicate that time-averaged powers above 1 mW can be readily obtained in very thin (diameter < 1 mm) and short (length < 15 mm) implants when ac fields that comply with safety standards are present in the tissues where the implants are located. The expressions and the in vitro models also indicate that the obtained dc power is maximized by delivering the ac field in the form of short bursts rather than continuously. The study results support the use of volume conduction as a safe option to power implants. INDEX TERMS Conducting materials, implantable biomedical devices, implantable electrodes, wireless power transmission. After working as a Research Engineer with the Translational Research and Knowledge Management Team (Research and Development), Otto Bock GmbH, Duderstadt, Germany, she became a Postdoctoral Fellow at UPF. Her research focuses mainly in exploring and designing miniaturized medical devices for sensing and electrical stimulation.

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

Minguillón

¹

,

Tudela-Pi

²

,

Becerra-Fajardo

³

et al. 2023

IEEE Trans. Biomed. Eng.

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Aiming at miniaturization, wireless power transfer (WPT) is frequently used in biomedical electronic implants as an alternative to batteries. However, WPT methods in use still require integrating bulky parts within the receiver, thus hindering the development of devices implantable by minimally invasive procedures, particularly when powers above 1 mW are required in deep locations. In this regard, WPT based on volume conduction of high frequency currents is an advantageous alternative relatively unexplored, and never demonstrated in humans. We describe an experimental study in which ac and dc electric powers in the order of milliwatts are obtained from pairs of needle electrodes (diameter = 0.4 mm, separation = 30 mm) inserted into the arms or lower legs of five healthy participants while innocuous and imperceptible high frequency (6.78 MHz) currents are delivered through two textile electrodes strapped around the considered limb. In addition, we demonstrate a procedure to model WPT based on volume conduction which characterizes coupling between the transmitters and the receivers by means of two-port impedance models which are generated from participants' medical images.

show abstract

Volume conduction energy transfer for implantable devices

Cited by 3 publications

References 15 publications

Powering electronic implants by high frequency volume conduction: in human validation

Powering electronic implants by high frequency volume conduction: in human validation

Power Transfer by Volume Conduction: In Vitro Validated Analytical Models Predict DC Powers Above 1 mW in Injectable Implants

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

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