High-performance wireless powering for peripheral nerve neuromodulation systems

<div><p>Neuromodulation of peripheral nerves with bioelectronic devices is a promising approach for treating a wide range of disorders. Wireless powering could enable long-term operation of these devices, but achieving high performance for miniaturized and deeply placed devices remains a technological challenge. We report the miniaturized integration of a wireless powering system in soft neuromodulation device (15 mm length, 2.7 mm diameter) and demonstrate high performance (about 10%) during <i>in vivo</i> wireless stimulation of the vagus nerve in a porcine animal model. The increased performance is enabled by the generation of a focused and circularly polarized field that enhances efficiency and provides immunity to polarization misalignment. These performance characteristics establish the clinical potential of wireless powering for emerging therapies based on neuromodulation.</p></div

Conformal wireless powering transmitter.

<p>A: Transmitter consisting of concentric metal rings. Adjacent rings are connected and loaded with reactive elements along the <i>x</i> and <i>y</i> axes to generate circularly polarized (CP) field or linearly polarized (LP) field. B: Simulated power transfer efficiency to a 20-mm straight dipole as a function of its orientation. The transmitter is placed above a tissue medium. The dipole is 10 mm deep in tissue. C: Contour plot of the electric field intensity generated by reactive elements along the <i>x</i> axis. D: Photograph of the transmitter. E: Numerically simulated and measured power transfer efficiency to a 20-mm long dipole as a function of its depth in tissue. F: Numerically simulated and measured power transfer efficiency over a curved surface. G: Simulated specific absorption ratio (SAR) using a human voxel model. Measured efficiency is recorded in saline solution. Simulations and measurements are performed at 2.4 GHz.</p

Performance and electrical properties of wireless cuff electrodes.

<p>A—C: Simulated performance of a 20-mm long straight dipole versus a 14-mm meandered dipole as a function of operating frequency. The dipoles are placed 10 mm deep in a tissue medium. D: Efficiency of the integrated circuits in converting radio-frequency power into current across loading impedances of 500 Ω and 1000 Ω (<i>n</i> = 2, minimum, mean, maximum). E: Real and imaginary parts of electrode impedance spectrum recorded in saline solution. F: Electrode impedance at 1 kHz after applying pulse train. Pulse train parameters, 25 Hz, 1 V amplitude, 500 <i>μ</i>s pulse width.</p

Real-time <i>in vivo</i> responses.

<p>First row records ECG waveform from lead III. Second row shows spikes extracted from the ECG waveform. Third row shows heart rate oscillation during 10-s alternating on-off stimulation. Forth row records blood pressure waveform. Fifth and sixth rows show the decrease in systolic and diastolic pressures during the 10-s alternating on-off stimulation.</p

Design of wireless cuff electrodes.

<p>A: Schematic diagram of a wireless cuff. The cuff consists of an array of electrodes, a meandered antenna, integrated circuits, and an inner channel wrapped around a nerve. B: Photos of the wireless cuff, and the embedded integrated circuits and antenna.</p