Rangarajan Jegadeesan

Topology Selection and Efficiency Improvement of Inductive Power Links

The problem of choosing the right topology for a wireless power transfer (WPT) application to maximize power transfer efficiency has been presented and addressed in this work. We analyze the series and parallel resonant topologies used in inductively coupled links, derive the efficiency expressions and verify them experimentally using planar inductors built on a PCB. We compare and contrast the two topologies and arrive at the frequency boundary that separates them. The results are verified experimentally and corroborated using simulation results from HFSS. We also address the misconception in the context of resonant tuning both qualitatively and quantitatively. Based on the analysis, we then provide the procedure to obtain the maximum power transfer efficiency for a given pair of coil across all frequencies, loads and topologies by proper selection of load, topology and the frequency of operation. The method is presented using an example pair of coils simulated in HFSS and the results agree well with the theoretical results.

Enabling Wireless Powering and Telemetry for Peripheral Nerve Implants

Wireless power delivery and telemetry have enabled completely implantable neural devices. Current day implants are controlled, monitored, and powered wirelessly, eliminating the need for batteries and prolonging the lifetime. A brief overview of wireless platforms for such implantable devices is presented in this paper alongside an in-depth discussion of wireless platform for peripheral nerve implants covering design requirements, link design, and safety. Initial acute studies on the performance of the wireless power and data links in rodents are also presented.

Inductive wireless power transmission for implantable devices

Inductive coupling is considered as one of the main stream techniques in wireless power transmission for implantable devices. In this paper, we present a generic analysis of the different topologies for wireless power transfer and arrive at boundary frequencies that separate various topologies, thereby allowing users to identify the topology that best suits the application requirements. In the meantime, we present a method of how to characterize and optimize rectangular coils used in inductive links for more general applications. Finally, preliminary results for retinal prosthesis applications are presented.

A study on the inductive power links for implantable biomedical devices

This paper presents a study on the efficiency of wireless power transfer (WPT) via inductive coupling, used in implantable biomedical devices. The expressions for efficiency of four different topologies used for WPT have been derived and a topology has been identified that is best suited for use with biomedical implants. The efficiency derived for the chosen topology is maximized and is compared with simulation results from ADS and they correlate well. A method has been proposed to select the components for SS topology to transfer the required power at maximum efficiency.

Wireless Power Delivery to Flexible Subcutaneous Implants Using Capacitive Coupling

Implantable devices need sustainable wireless powering for safe long-term operations. In this paper, we present a near-field capacitive coupling (NCC)-based wireless powering scheme to transfer power to implants efficiently. By modeling the power link, we identify that the optimal operating frequency of the NCC scheme for subcutaneous power delivery is in the sub-GHz frequency range. The proposed scheme has desirable features, such as flexible and conformal power receiver realizations, and complies well with IEEE C95.1 specific absorption rate safety standards. The NCC link was designed and tested in a nonhuman primate cadaver, and the experimental results showed that it could safely deliver up to 100 mW of power to an implant with a peak operating efficiency of over 50%. A bending deformation study of the transmitter–receiver patches was also performed to demonstrate the reliability of the NCC powering scheme, in realistic postimplantation scenarios. Our studies validate the NCC method as a safe wireless powering scheme, which can be used as an alternative to the near-field resonant inductive coupling method, for chronic use in subcutaneous implants.

Electric near-field coupling for wireless power transfer in biomedical applications

Wireless power transfer for biomedical implants using capacitive coupling (electric near field coupling) has been presented in this work as an attractive alternative to the traditional inductive coupling method with the benefits of simple topology, fewer components on the implant side, better EMI performance and robustness to surrounding metallic elements. The analysis and design of capacitive coupled power link for biomedical implants is presented with emphasis on modeling tissue losses. Design and evaluation of capacitive power link has been presented with experimental results that are verified using the theoretical model developed.

Wireless Power Transfer Strategies for Implantable Bioelectronics: Methodological Review

Neural implants have emerged over the last decade as highly effective solutions for the treatment of dysfunctions and disorders of the nervous system. These implants establish a direct, often bidirectional, interface to the nervous system, both sensing neural signals and providing therapeutic treatments. As a result of the technological progress and successful clinical demonstrations, completely implantable solutions have become a reality and are now commercially available for the treatment of various functional disorders. Central to this development is the wireless power transfer (WPT) that has enabled implantable medical devices (IMDs) to function for extended durations in mobile subjects. In this review, we present the theory, link design, and challenges, along with their probable solutions for the traditional near-field resonant inductively coupled WPT, capacitively coupled short-ranged WPT, and more recently developed ultrasonic, mid-field, and far-field coupled WPT technologies for implantable applications. A comparison of various power transfer methods based on their power budgets and WPT range follows. Power requirements of specific implants like cochlear, retinal, cortical, and peripheral are also considered and currently available IMD solutions are discussed. Patients safety concerns with respect to electrical, biological, physical, electromagnetic interference, and cyber security from an implanted neurotech device are also explored in this review. Finally, we discuss and anticipate future developments that will enhance the capabilities of current-day wirelessly powered implants and make them more efficient and integrable with other electronic components in IMDs.

Overcoming coil misalignment using magnetic fields of induced currents in wireless power transmission

Coil Misalignment in wireless power transfer links that use inductive coupling has limited the wireless power transfer efficiency considerably. Motion artifacts leading to coil misalignments also results in intermittent power outage at the receiving coil. In this paper, we address these issues using the concept of flux sharing between three coils. By using magnetic fields of induced currents in an intermediate coil, the flux linkage between a traditional two coil inductive power links can be improved. We present the analysis of inductive power links with intermediate coils and compare their improved performance with the conventional wireless power links. The mitigation of detrimental effects of motion artifacts is also discussed. All the theoretical results augur well with the measured results.

Synthetic skins with humanlike warmth

Synthetic skins with humanlike characteristics, such as a warm touch, may be able to ease the social stigma associated with the use of prosthetic hands by enabling the user to conceal its usage during social touching situations. Similarly for social robotics, artificial hands with a warm touch have the potential to provide touch that can give comfort and care for humans. With the aim of replicating the warmth of human skin, this paper describes (i) the experiments on obtaining the human skin temperature at the forearm, palm and finger, (ii) embedding and testing a flexible heating element on two types of synthetic skins and (iii) implementing a power control scheme using the pulse-width modulation to overcome the limitations of operating at different voltage levels and sources. Results show that the surface temperature of the human skin can be replicated on the synthetic skins.

In Vivo Testing of Circularly Polarized Implantable Antennas in Rats

Two types of miniaturized circularly polarized (CP) implantable antennas are tested in a rat to investigate the effects of the live tissue on the antenna performance. The two implantable antennas are designed for Industrial, Scientific, and Medical (ISM) (2.4-2.48 GHz) biomedical applications. The first implantable helical antenna is initially designed in a one-layer muscle phantom for ingestible capsule endoscope systems. The second implantable patch antenna is designed in a one-layer skin phantom for wireless implantable devices with a fixed implant position. The footprint of the proposed antennas are π×(5.5)2 ×3.81 mm3 and 10 ×10 ×1.27 mm3, respectively. The two antennas were surgically implanted into the rat at Singapore Institute for Neurotechnology. The measured results in the rat were compared to the simulated ones in the one-layer phantom to evaluate the sensitivity of the antennas.