A 430-MHz Wirelessly Powered Implantable Pulse Generator With Intensity/Rate Control and Sub-1 μA Quiescent Current Consumption

Vagus nerve stimulation using a miniaturized wirelessly powered stimulator in pigs

Neuromodulation of peripheral nerves has been clinically used for a wide range of indications. Wireless and batteryless stimulators offer important capabilities such as no need for reoperation, and extended life compared to their wired counterparts. However, there are challenging trade-offs between the device size and its operating range, which can limit their use. This study aimed to examine the functionality of newly designed wirelessly powered and controlled implants in vagus nerve stimulation for pigs. The implant used near field inductive coupling at 13.56 MHz industrial, scientific, and medical band to harvest power from an external coil. The circular implant had a diameter of 13 mm and weighed 483 mg with cuff electrodes. The efficiency of the inductive link and robustness to distance and misalignment were optimized. As a result, the specific absorption rate was orders of magnitude lower than the safety limit, and the stimulation can be performed using only 0.1 W of external power. For the first time, wireless and batteryless VNS with more than 5 cm operation range was demonstrated in pigs. A total of 84 vagus nerve stimulations (10 s each) have been performed in three adult pigs. In a quantitative comparison of the effectiveness of VNS devices, the efficiency of systems on reducing heart rate was similar in both conventional (75%) and wireless (78.5%) systems. The pulse width and frequency of the stimulation were swept on both systems, and the response for physiological markers was drawn. The results were easily reproducible, and methods used in this study can serve as a basis for future wirelessly powered implants.

Towards a Leadless Wirelessly Controlled Intravenous Cardiac Pacemaker

OBJECTIVE

Traditional lead-based cardiac pacemakers suffer from lead-related complications including lead fracture, lead dislodgement, and venous obstruction. Modern leadless pacemakers mitigate the complications, but since they are implanted inside the heart with a small battery, their limited battery lifetime necessities device replacement within the patient's lifetime. This paper presents a leadless and batteryless, wirelessly powered intravenous cardiac pacemaker that can potentially mitigate both problems.

METHODS

Wireless power is transferred at 13.56 MHz in bursts between the pacemaker modules to achieve sufficient power over the required distance for wireless pacing. The pacemaker stimulation module is designed to fit within the anatomical constraints of a cardiac vein, consume low power, apply greater than 5V stimulation and comply with FCC SAR regulations. The module is primarily implemented in CMOS technology to achieve extreme system miniaturization.

RESULTS

Ex-vivo pacing capability was demonstrated with a system that can apply 5V stimulation, consume 1mW power, and operate up to 2.5cm TX and RX separation. An in-vivo experiment verified the pacemaker functionality by increasing the heartbeat of Yorkshire pig from 64bpm to 100bpm.

CONCLUSION

This work establishes that intravascular cardiac pacing can be achieved that can mitigate lead and battery-related complications.

SIGNIFICANCE

This study has a potential to advance leadless and wirelessly powered pacemaker technology.

A simple method for implanting free-floating microdevices into the nervous tissue

Objective. Free-floating implantable neural interfaces are an emerging powerful paradigm for mapping and modulation of brain activity. Minuscule wirelessly-powered devices have the potential to provide minimally-invasive interactions with neurons in chronic research and medical applications. However, these devices face a seemingly simple problem-how can they be placed into nervous tissue rapidly, efficiently and in an essentially arbitrary location?Approach. We introduce a novel injection tool and describe a controlled injection approach that minimizes damage to the tissue.Main results.To validate the needle injectable tool and the presented delivery approach, we evaluate the spatial precision and rotational alignment of the microdevices injected into agarose, brain, and sciatic nerve with the aid of tissue clearing and MRI imaging. In this research, we limited the number of injections into the brain to four per rat as we are using microdevices that are designed for an adult head size on a rat model. We then present immunohistology data to assess the damage caused by the needle.Significance. By virtue of its simplicity, the proposed injection method can be used to inject microdevices of all sizes and shapes and will do so in a fast, minimally-invasive, and cost-effective manner. As a result, the introduced technique can be broadly used to accelerate the validation of these next-generation types of electrodes in animal models.

A mm-Sized Free-Floating Wireless Implantable Opto-Electro Stimulation Device

Towards a distributed neural interface, consisting of multiple miniaturized implants, for interfacing with large-scale neuronal ensembles over large brain areas, this paper presents a mm-sized free-floating wirelessly-powered implantable opto-electro stimulation (FF-WIOS2) device equipped with 16-ch optical and 4-ch electrical stimulation for reconfigurable neuromodulation. The FF-WIOS2 is wirelessly powered and controlled through a 3-coil inductive link at 60 MHz. The FF-WIOS2 receives stimulation parameters via on-off keying (OOK) while sending its rectified voltage information to an external headstage for closed-loop power control (CLPC) via load-shift-keying (LSK). The FF-WIOS2 system-on-chip (SoC), fabricated in a 0.35-µm standard CMOS process, employs switched-capacitor-based stimulation (SCS) architecture to provide large instantaneous current needed for surpassing the optical stimulation threshold. The SCS charger charges an off-chip capacitor up to 5 V at 37% efficiency. At the onset of stimulation, the capacitor delivers charge with peak current in 1.7–12 mA range to a micro-LED (µLED) array for optical stimulation or 100–700 μA range to a micro-electrode array (MEA) for biphasic electrical stimulation. Active and passive charge balancing circuits are activated in electrical stimulation mode to ensure stimulation safety. In vivo experiments conducted on three anesthetized rats verified the efficacy of the two stimulation mechanisms. The proposed FF-WIOS2 is potentially a reconfigurable tool for performing untethered neuromodulation.

Synchronized Biventricular Heart Pacing in a Closed-chest Porcine Model based on Wirelessly Powered Leadless Pacemakers

About 30% of patients with impaired cardiac function have ventricular dyssynchrony and seek cardiac resynchronization therapy (CRT). In this study, we demonstrate synchronized biventricular (BiV) pacing in a leadless fashion by implementing miniaturized and wirelessly powered pacemakers. With their flexible form factors, two pacemakers were implanted epicardially on the right and left ventricles of a porcine model and were inductively powered at 13.56 MHz and 40.68 MHz industrial, scientific, and medical (ISM) bands, respectively. The power consumption of these pacemakers is reduced to µW-level by a novel integrated circuit design, which considerably extends the maximum operating distance. Leadless BiV pacing is demonstrated for the first time in both open-chest and closed-chest porcine settings. The clinical outcomes associated with different interventricular delays are verified through electrophysiologic and hemodynamic responses. The closed-chest pacing only requires the external source power of 0.3 W and 0.8 W at 13.56 MHz and 40.68 MHz, respectively, which leads to specific absorption rates (SARs) 2–3 orders of magnitude lower than the safety regulation limit. This work serves as a basis for future wirelessly powered leadless pacemakers that address various cardiac resynchronization challenges.

Stretchable Transparent Wireless Charging Coil Fabricated by Negative Transfer Printing

Wearable electronics, such as smartwatches, VR (virtual reality)/AR (augmented reality) smartglasses, and E-textiles, are an emerging technology platform that is reshaping the way people interact with the surrounding world. However, the power source of these devices can be a critical issue, causing short operational/standby times and frequent charging. Here, a stretchable transparent wireless charging coil fabricated by negative adhesive transfer printing (NATP) is demonstrated. The stretchable transparent conductor is based on the silver nanowire (AgNW)-polyurethane acrylate (PUA) composite with high conductivity and robustness under harsh mechanical treatment. A 10.6 ohm/sq thin film has a transmittance of 84% and is still conductive under a mechanical deformation up to 60% tensile strain. A maximum power of 59 mW (power transfer efficiency ∼24%) is transferred wirelessly. A green-light-emitting diode (LED) was wirelessly powered to illustratively demonstrate the functionality of the system. This work provides an alternative power solution which is compatible with the soft and flexible components of wearable devices.