A novel analytical model of inductively coupled wireless power transfer is presented. For the first time, the effects of coil misalignment and geometry are addressed in a single mathematical expression. In the applications envisaged, such as radio frequency identification (RFID) and biomedical implants, the receiving coil is normally significantly smaller than the transmitting coil. Formulas are derived for the magnetic field at the receiving coil when it is laterally and angularly misaligned from the transmitting coil. Incorporating this magnetic field solution with an equivalent circuit for the inductive link allows us to introduce a power transfer formula that combines coil characteristics and misalignment factors. The coil geometries considered are spiral and short solenoid structures which are currently popular in the RFID and biomedical domains. The novel analytical power transfer efficiency expressions introduced in this study allow the optimization of coil geometry for maximum power transfer and misalignment tolerance. The experimental results show close correlation with the theoretical predictions. This analytic technique can be widely applied to inductive wireless power transfer links without the limitations imposed by numerical methods.

Wireless Power Transfer in Loosely Coupled Links: Coil Misalignment Model

Global hearing health care: new findings and perspectives

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. Patient's 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.

Wireless Power Transfer Strategies for Implantable Bioelectronics

Electrical neuromodulation of lumbar segments improves motor control after spinal cord injury in animal models and humans. However, the physiological principles underlying the effect of this intervention remain poorly understood, which has limited the therapeutic approach to continuous stimulation applied to restricted spinal cord locations. Here we developed stimulation protocols that reproduce the natural dynamics of motoneuron activation during locomotion. For this, we computed the spatiotemporal activation pattern of muscle synergies during locomotion in healthy rats. Computer simulations identified optimal electrode locations to target each synergy through the recruitment of proprioceptive feedback circuits. This framework steered the design of spatially selective spinal implants and real-time control software that modulate extensor and flexor synergies with precise temporal resolution. Spatiotemporal neuromodulation therapies improved gait quality, weight-bearing capacity, endurance and skilled locomotion in several rodent models of spinal cord injury. These new concepts are directly translatable to strategies to improve motor control in humans.

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Spatiotemporal neuromodulation therapies engaging muscle synergies improve motor control after spinal cord injury

From the first pacemaker implant in 1958, numerous engineering and medical activities for implantable medical device development have faced challenges in materials, battery power, functionality, electrical power consumption, size shrinkage, system delivery, and wireless communication. With explosive advances in scientific and engineering technology, many implantable medical devices such as the pacemaker, cochlear implant, and real-time blood pressure sensors have been developed and improved. This trend of progress in medical devices will continue because of the coming super-aged society, which will result in more consumers for the devices. The inner body is a special space filled with electrical, chemical, mechanical, and marine-salted reactions. Therefore, electrical connectivity and communication, corrosion, robustness, and hermeticity are key factors to be considered during the development stage. The main participants in the development stage are the user, the medical staff, and the engineer or technician. Thus, there are three different viewpoints in the development of implantable devices. In this review paper, considerations in the development of implantable medical devices will be presented from the viewpoint of an engineering mind.

/pdf/development-of-implantable-medical-devices-from-an-1ubw5n62jm.pdf

Development of Implantable Medical Devices: From an Engineering Perspective

As the most successful neural prosthesis, cochlear implants have provided partial hearing to more than 120000 persons worldwide; half of which being pediatric users who are able to develop nearly normal language. Biomedical engineers have played a central role in the design, integration and evaluation of the cochlear implant system, but the overall success is a result of collaborative work with physiologists, psychologists, physicians, educators, and entrepreneurs. This review presents broad yet in-depth academic and industrial perspectives on the underlying research and ongoing development of cochlear implants. The introduction accounts for major events and advances in cochlear implants, including dynamic interplays among engineers, scientists, physicians, and policy makers. The review takes a system approach to address critical issues in cochlear implant research and development. First, the cochlear implant system design and specifications are laid out. Second, the design goals, principles, and methods of the subsystem components are identified from the external speech processor and radio frequency transmission link to the internal receiver, stimulator and electrode arrays. Third, system integration and functional evaluation are presented with respect to safety, reliability, and challenges facing the present and future cochlear implant designers and users. Finally, issues beyond cochlear implants are discussed to address treatment options for the entire spectrum of hearing impairment as well as to use the cochlear implant as a model to design and evaluate other similar neural prostheses such as vestibular and retinal implants.

Cochlear Implants: System Design, Integration, and Evaluation

https://escholarship.org/content/qt30w8t1z1/qt30w8t1z1.pdf

Development and evaluation of the Nurotron 26-electrode cochlear implant system

An integrated vestibular-cochlear implant can be rapidly prototyped and clinically tested by modifying an existing modern cochlear implant. The modifications include addition of gyroscope sensors and reallocation of several electrodes that are normally used for auditory nerve stimulation to the semicircular canals, while sharing the external DSP processor and the internal receiver/stimulator. This paper discusses the validation issues related to hardware and software design that arise in integrating electric hearing and balance onto a single device. The device's initially targeted population will be deaf individuals who also have vestibular impairment since there is a strong ethical justification for vestibular implantation along with minimal additional surgical risk. Because of widespread usage of ototoxic drugs and unique genetic mutations, the patient population with both impaired hearing and balance function is especially prevalent in Asian countries such as China and India. Should such an integrated vestibular-cochlear implant be verified, it could be used to restore balance or treat a wide array of vestibular disorders.

An integrated vestibular-cochlear prosthesis for restoring balance and hearing

The invention discloses a totally implanted artificial cochlea system. The system comprises a stimulating electrode, a stimulation processing part connected with the stimulating electrode, a sensing part connected with the stimulation processing part, an antenna part connected with the stimulation processing part, a power source part connected with the stimulation processing part, and an in-vitro charging part. The stimulation processing part comprises a first connection unit, an analog-digital conversion unit, a central management and communication unit, a signal processing device and a stimulator chip. The power source part comprises a second connection unit, a digital-analog conversion unit, a charging micro-control unit and a charging coil. A traditional artificial cochlea system needing an in-vivo part and an in-vitro part can be improved into a totally implanted artificial cochlea system, the in-vitro part is not needed, in the aspect of function, 24-hour sound listening and waterproof and dustproof performance are guaranteed, and in the aspect of user experience, the whole system is completely hidden and the appearance of a user is not different from that of a normal person.

Totally implanted artificial cochlea system

The present invention discloses a totally-implantable hybrid power supply cochlear implant system. The totally-implantable hybrid power supply cochlear implant system comprises a stimulation electrode, a hybrid stimulation chip, a signal processing unit, a central control unit, a decoding and demodulation unit, a sensor and a charging unit; the hybrid stimulation chip is connected with the stimulation electrode; the signal processing unit is connected with the hybrid stimulation chip, the central control unit, the decoding and demodulation unit and the sensor; the central control unit is connected with the signal processing unit and the charging unit; the decoding and demodulation unit is connected with the signal processing unit and the charging unit; and the charging unit is connected with the central control unit and the decoding and demodulation unit. According to the totally-implantable hybrid power supply cochlear implant system of the invention, a traditional cochlear implant system which is composed of two parts in vivo and in vitro respectively is improved to a totally-implantable cochlear implant system, and after the service life of an in-vivo charging battery is expired, the totally-implantable hybrid power supply cochlear implant system can be matched with an in-vitro speech processor so as to continue to work.

Sun Xiao'an

Papers

Cochlear Implants: System Design, Integration, and Evaluation

Development and evaluation of the Nurotron 26-electrode cochlear implant system

An integrated vestibular-cochlear prosthesis for restoring balance and hearing

Totally implanted artificial cochlea system

Totally-implantable hybrid power supply cochlear implant system