Cavity Resonator Wireless Power Transfer System for Freely Moving Animal Experiments.

OBJECTIVE: The goal of this paper is to create a large wireless powering arena for powering small devices implanted in freely behaving rodents. METHODS: We design a cavity resonator based wireless power transfer (WPT) system and utilize our previously developed optimal impedance matching methodology to achieve effective WPT performance for operating sophisticated implantable devices, made with miniature receive coils (<8 mm in diameter), within a large volume (dimensions: 60.96 cm × 60.96 cm × 30 cm). We provide unique cavity design and construction methods which maintains electromagnetic performance of the cavity while promoting its utility as a large animal husbandry environment. In addition, we develop a biaxial receive resonator system to address device orientation insensitivity within the cavity environment. Functionality is demonstrated with chronic experiments involving rats implanted with our custom designed bioelectric recording device. RESULTS: We demonstrate an average powering fidelity of 93.53% over nine recording sessions across nine weeks, indicating nearly continuous device operation for a freely behaving rat within the large cavity resonator space. CONCLUSION: We have developed and demonstrated a cavity resonator based WPT system for long term experiments involving freely behaving small animals. SIGNIFICANCE: This cavity resonator based WPT system offers an effective and simple method for wirelessly powering miniaturized devices implanted in freely moving small animals within the largest space.

Enhancing the versatility of wireless biopotential acquisition for myoelectric prosthetic control.

OBJECTIVE: A significant challenge in rehabilitating upper-limb amputees with sophisticated, electric-powered prostheses is sourcing reliable and independent channels of motor control information sufficient to precisely direct multiple degrees of freedom simultaneously. APPROACH: In response to the expressed needs of clinicians, we have developed a miniature, batteryless recording device that utilizes emerging integrated circuit technology and optimal impedance matching for magnetic resonantly coupled (MRC) wireless power transfer to improve the performance and versatility of wireless electrode interfaces with muscle. MAIN RESULTS: In this work we describe the fabrication and performance of a fully wireless and batteryless EMG recording system and use of this system to direct virtual and electric-powered limbs in real-time. The advantage of using MRC to optimize power transfer to a network of wireless devices is exhibited by EMG collected from an array of eight devices placed circumferentially around a human subject's forearm. SIGNIFICANCE: This is a comprehensive, low-cost, and non-proprietary solution that provides unprecedented versatility of configuration to direct myoelectric prostheses without wired connections to the body. The amenability of MRC to varied coil geometries and arrangements has the potential to improve the efficiency and robustness of wireless power transfer links at all levels of upper-limb amputation. Additionally, the wireless recording device's programmable flash memory and selectable features will grant clinicians the unique ability to adapt and personalize the recording system's functional protocol for patient- or algorithm-specific needs.

Magnetically Inserted Neural Electrodes: Tissue Response and Functional Lifetime.

Neural recording and stimulation have great clinical potential. Long-term neural recording remains a challenge, however, as implantable electrodes eventually fail due to the adverse effects of the host tissue response to the indwelling implant. Astrocytes and microglia attempt to engulf the electrode, increasing the electrical impedance between the electrode and neurons, and possibly pushing neurons away from the recording site. Faster insertion speed, finer tip geometry, smaller size, and lower material stiffness all seem to decrease damage caused by insertion and reduce the intensity of the tissue response. However, electrodes that are too small result in buckling, making insertion impossible. In this paper, we assess the viability of high-speed (27.8 m/s) deployment of 25 µm, ferromagnetic microelectrodes into rat brain. To characterize functionality of magnetically inserted electrodes, 4 Long-Evans rats were implanted for 31 days with impedance measurements and neural recordings taken daily. Performance was compared to 150 µm diameter PlasticsOne electrodes since 25 µm electrodes buckled during "slow speed" insertion. Platinum-iron magnetically inserted electrodes resolved single unit activity throughout the duration of the study in one rat, and saw no significant change (p=0.970) in impedance (4.54% increase) from day 0 (Z0 ≈ 144 kΩ,Z31 ≈ 150 kΩ). These findings provide a proof-of-concept for magnetic insertion as a viable insertion method that enables nonbuckling implantation of small (25 µm) microelectrodes, with potential for neural recording applications.

Current state of craniofacial prosthetic rehabilitation.

PURPOSE: This study aimed to review the current state of the techniques and materials used to rehabilitate maxillofacial defects. MATERIALS AND METHODS: The MEDLINE and EMBASE databases were searched for articles pertinent to maxillofacial prostheses published from January 1990 to July 2011. The main clinical stages were the subject of analysis. RESULTS: A multidisciplinary approach is preferred when rehabilitating maxillofacial defects. Surgical reconstruction can be used for smaller defects, but larger defects require a prosthesis to achieve an esthetic rehabilitation. Implant retained prostheses are preferred over adhesive prostheses. Silicone elastomer is currently the best material available for maxillofacial prostheses; however, longevity and discoloration, which are greatly influenced by ultraviolet radiation, microorganisms, and environmental factors, remain significant problems. In the near future, the widespread availability and cost effectiveness of digital systems may improve the workflow and outcomes of facial prostheses. Patients report high satisfaction with their prostheses despite some areas that still need improvement. CONCLUSIONS: Maxillofacial prostheses are a reliable treatment option to restore maxillofacial defects and improve quality of life. Significant progress has been made in the application of implants for retention and digital technology for designing surgical guides, suprastructures, and craniofacial prostheses. Further improvements are necessary to enhance longevity of prostheses.