John E. Ferguson

Wireless communication with implanted medical devices using the conductive properties of the body.

Many medical devices that are implanted in the body use wires or wireless radiofrequency telemetry to communicate with circuitry outside the body. However, the wires are a common source of surgical complications, including breakage, infection and electrical noise. In addition, radiofrequency telemetry requires large amounts of power and results in low-efficiency transmission through biological tissue. As an alternative, the conductive properties of the body can be used to enable wireless communication with implanted devices. In this article, several methods of intrabody communication are described and compared. In addition to reducing the complications that occur with current implantable medical devices, intrabody communication can enable novel types of miniature devices for research and clinical applications.

IBCOM (intra-brain communication) microsystem: Wireless transmission of neural signals within the brain

We report our preliminary work to explore a new method of signal transmission for bio-implantable microsystems. Intra-brain communication or IBCOM is a wireless signal transmission method that uses the brain itself as a conductive medium to transmit the data and commands between neural implants and data processing systems outside the brain. Two miniaturized IBCOM (µ-IBCOM) CMOS chips were designed and fabricated for an in vivo test bed to transmit two prerecorded neural signals at different binary frequency shift keying (BFSK) carrier frequencies to validate the feasibility of IBCOM concept. The chips were packaged for full implantation in a rat brain except for external power delivery. The original neural signal waveforms were successfully recovered after being transmitted between two platinum electrodes separated by 15 mm with transmission power less than 650 pJ/bit for the CMOS implementation.

Nanowires precisely grown on the ends of microwire electrodes permit the recording of intracellular action potentials within deeper neural structures.

AIMS Nanoelectrodes are an emerging biomedical technology that can be used to record intracellular membrane potentials from neurons while causing minimal damage during membrane penetration. Current nanoelectrode designs, however, have low aspect ratios or large substrates and thus are not suitable for recording from neurons deep within complex natural structures, such as brain slices. MATERIALS & METHODS We describe a novel nanoelectrode design that uses nanowires grown on the ends of microwire recording electrodes similar to those frequently used in vivo. RESULTS & DISCUSSION We demonstrate that these nanowires can record intracellular action potentials in a rat brain slice preparation and in isolated leech ganglia. CONCLUSION Nanoelectrodes have the potential to revolutionize intracellular recording methods in complex neural tissues, to enable new multielectrode array technologies and, ultimately, to be used to record intracellular signals in vivo.

Pilot study of strap-based custom wheelchair seating system in persons with spinal cord injury.

Custom wheelchair seats can be used to help prevent pressure ulcers in individuals with spinal cord injury. In this study, a strap-based system was evaluated in three Veterans with spinal cord injury. Interface pressure distributions were measured after transfers, wheeling, and pressure relief maneuvers and after fittings by three different therapists. We found that pressure distribution measures were not generally affected after transfers and wheeling using the strap-based wheelchair and that pressure relief maneuvers were able to be performed. Additionally, all therapists were able to customize the wheelchair seat to clinically acceptable levels in 4 to 40 min for the three subjects. Future studies can test the long-term effects of using the strap-based wheelchair seat and identifying individuals that would most benefit from a rapidly customizable wheelchair seat.

Improving Automatic Control of an Ankle-Foot Prosthesis Using Machine Learning Algorithms

Most commercially available lower-limb prostheses are designed for walking, not for standing. The Minneapolis VA Health Care System has developed a bimodal prosthetic anklefoot system with distinct modes for walking and standing [1]. With this device, a prosthesis user can select standing or walking mode in order to maximize standing stability or walking functionality, depending on the activity and context. Additionally, the prosthesis was designed to allow for an “automatic mode” to switch between standing and walking modes based on readings from an onboard Inertial Measurement Unit (IMU) without requiring user interaction to manually switch modes. A smartphone app was also developed to facilitate changing between walking, standing and automatic modes. The prosthesis described in [1] was used in a pilot study with 18 Veterans with lower-limb amputations to test static, dynamic, and functional postural stability. As part of the study, 17 Veterans were asked for qualitative feedback on the bimodal ankle-foot system (Table 1).

Bimodal ankle-foot prosthesis for enhanced standing stability

Previous work suggests that to restore postural stability for individuals with lower-limb amputation, ankle-foot prostheses should be designed with a flat effective rocker shape for standing. However, most commercially available ankle-foot prostheses are designed with a curved effective rocker shape for walking. To address the demands of both standing and walking, we designed a novel bimodal ankle-foot prosthesis that can accommodate both functional modes using a rigid foot plate and an ankle that can lock and unlock. The primary objective of this study was to determine if the bimodal ankle-foot system could improve various aspects of standing balance (static, dynamic, and functional) and mobility in a group of Veterans with lower-limb amputation (n = 18). Standing balance was assessed while subjects completed a series of tests on a NeuroCom Clinical Research System (NeuroCom, a Division of Natus, Clackamas, OR), including a Sensory Organization Test, a Limits of Stability Test, and a modified Motor Control Test. Few statistically significant differences were observed between the locked and unlocked ankle conditions while subjects completed these tests. However, in the absence of visual feedback, the locked bimodal ankle appeared to improve static balance in a group of experienced lower-limb prosthesis users whose PLUS-M mobility rating was higher than approximately 73% of the sample population used to develop the PLUS-M survey. Given the statistically significant increase in mean equilibrium scores between the unlocked and locked conditions (p = 0.004), future testing of this system should focus on new amputees and lower mobility users (e.g., Medicare Functional Classification Level K1 and K2 prosthesis users). Furthermore, commercial implementation of the bimodal ankle-foot system should include a robust control system that can automatically switch between modes based on the user’s activity.

Wireless Galvanic Transmission Through Neural Tissue Via Modulation of a Carrier Signal by A Passive Probe

MARCH 2012, Vol. 6 / 017509-1 Wireless Galvanic transmission through neural tissue via modulation of a carrier signal by a passive probe Andrew E. Papale Graduate Program in Neuroscience, Univ. Minnesota Ryan Mork Dept. Electrical & Computer Engineering, U Minnesota Chris Boldt Department of Neuroscience, Univ. Minnesota Jadin C. Jackson Department of Biology, University of St. Thomas John E. Ferguson Medical Devices Center Fellow, Univ. Minnesota A. David Redish Department of Neuroscience University of Minnesota

The Neural Nanoprobe: Physically Decoupling the Neural Recording Site From the Headstage

The ability to record neural ensembles from awake, behaving nimals is one of the most important and successful components f the neuroscience experimental toolbox. However, even the ost advanced modern systems have limitations due to the physial coupling of the recording site with the headstage. These sysems can only record from a limited number of structures at any ne time and have particular difficulty recording large ensembles rom animals with thin skulls e.g., mice, songbirds . Current sysems cannot record from fragile structures spinal cord, peripheral erves and ganglia during behavior because the wire electrodes ould shred the fragile nerves as the animal moves. We propose he concept of a neural nanoprobe that is physically decoupled rom a separately implanted waystation. Because the nanoprobes re not connected to the waystation by physical wires, multiple anoprobes could be placed in multiple neural structures, all trans-

Creating Low-Impedance Coatings for Neural Recording Electrodes Using Electroplating Inhibitors

Temperature and pH-sensitive ABC triblock polymers were preared to form hydrogel membranes capable of changing their tructure in response to environmental stimuli, allowing drug reease, from a micro implantable device, in short and repetitive ulses. We have previously investigated the capacity of hydrogels o sustain open loop oscillatory behavior, with application in hythmic hormone release. This novel oscillator is mediated by eedback instability between swelling/shrinking of the hydrogel nd an enzyme reaction, whose product modifies pH in the hydroel. The objective of this work was to prepare and characterize riblock polymer-based hydrogels, to overcome limitations of conentional hydrogels. Our strategy involves reversible arrangement f A and C thermosensitive domains within a strong network, hereas B block is also pH-sensitive. The triblock was mainly ased on the use of NIPAAm N, isopropylacrylamide and AA acrylic acid monomers. Polymers were synthesized by reversible