Bionode5.0: A miniature, wireless, closed-loop biological implant for neuromodulation

The needs for electrotherapy, using electrical devices, are significantly increasing, due to limitations that pharmaceutical therapies may have, such as unignorable side effects and meager side effects on a multitude of cardiovascular and neurological diseases. To research on electrotherapy using an implantable electronic module, a miniature, wireless, and closed-loop implantable device, called Bionode , has been developed at Center for Implantable Device, directed by Dr. Pedro Irazoqui. Bionode4.1, the most recent version of the Bionode, is a device that consists of three different printed circuit boards(PCB), including a wireless communication system, an inductive power receiving system, and a two-channel recording system with a stimulator that has an ability to output a biphasic constant current stimulation. However, a few issues were brought to the surface during the fabrication process and in-vivo animal tests: 1) Unwanted data loss due to the failure of communication between the device and the Base Station, 2) stimulator\u27s imbalanced output with glitches and noise, 3) structural complexity that made debugging and constructing the device difficult, 4) device configuration, which could not be customized for the specific applications. These limitations found in Bionode 4.1 led to the development of the new version of Bionode, Bionode 5.0 . In order to increase the fidelity of the data transmission, a meandered inverted F trace antenna, which can cover the 2.4 GHz industrial, scientific, and medical (ISM) radio band, was designed and implemented in the wireless communication system of the Bionode 5.0. In order to resolve the stimulation issue, the old stimulator built in Bionode 4.1 was replaced with an upgraded stimulation circuitry that consists of the additional feedback system and the switches for suppressing the imbalanced pulses and controlling the unwanted glitches on the output. Re-optimizing the overall floor plan of the device and utilizing a new type of board-to-board connector solved the issues related to the structure and customizability. As a result, Bionode 5.0 with the smaller volume and the larger utilizable surface area resolved the issues that Binode4.1 had and would potentially allow the users to widely utilize the new version in various applications for the medical research

Development of a Wearable Haptic Feedback Device for Upper Limb Prosthetics through Sensory Substitution

Haptics can enable a direct communication pipeline between the artificial limb and the brain; adding haptic sensory feedback for prosthesis wearers is believed to improve operation without drawing too much of the user\u27s attention. Through neuroplasticity, the brain can become more cognizant of the information delivered through the skin and may eventually interpret it as inherently as other natural senses. In this thesis, a wearable haptic feedback device (WHFD) is developed to communicate prosthesis sensory information. A 14-week, 6-stage, between subjects study was created to investigate the learning trajectory as participants were stimulated with haptic patterns conveying joint proprioception. 37 healthy participants were divided into three groups, with each group assigned a different haptic stimulation method (τ0, τ1 or τ2). 18 participants managed to complete the study within 7{14 sessions, demonstrating that participants were, in fact, learning to interpret the haptic information. Participants in group τ2 had some advantages in interpreting the haptic information over the others; however, each stimulation method has advantages that can be exploited and hybridized for future models of the WHFD. Learning rates within groups were highly variable and deterred significantly with increasing quantities of simultaneous information. A secondary investigation determined strategies to improve the ability of the haptic actuators to transfer information to the user, which will be employed for future prototypes. Overall, the proposed WHFD is an effective device that can promote greater sensory awareness for wearers of prostheses

Neural Interfacing with Dorsal Root Ganglia: Anatomical Characterization and Electrophysiological Recordings with Novel Electrode Arrays

Dorsal root ganglia (DRG), the hubs of neurons conducting sensory information into the spinal cord, are promising targets for clinical and investigative neural interface technologies. DRG stimulation is currently a tertiary therapy for chronic pain patients, which has an estimated prevalence of 11-40% of adults in the United States. In pre-clinical studies, combined neural recording and stimulation at DRG has been used as part of closed-loop systems to drive activity of the limbs and the urinary system. This suggests a role for clinical DRG interfaces to assist, among other patient groups, the nearly 300,000 spinal cord injured patients in the United States. To maximize the utility of DRG interfaces, however, there remains a strong need to improve our understanding of DRG structure. Neural interface technologies for both stimulation and recording rely heavily on the spatial organization of their neural targets. To record high-fidelity neural signals, a microelectrode must be placed within about 200 µm of a neural cell body. Likewise, effective neural stimulation is believed to act on a subset of DRG axons based on their size and target. The spatial organization of DRG, however, has not been previously quantified. In this thesis, I demonstrate a novel algorithm to transform histological cross-sections of DRG to a normalized circular region for quantifying trends across many samples. Using this algorithm on 26 lumbosacral DRG from felines, a common preclinical DRG model, I found that the highest density of neural cell bodies was in the outer 24% radially, primarily at the dorsal aspect. I extended this analysis to a semi-automated cross-DRG analysis in 33 lower lumbar DRG from 10 human donors. I found that the organization of human DRG was similar to felines, with the highest density of cell bodies found in the outer 20-25% of the DRG, depending on spinal level. I also found a trend toward lower small-axon density at the dorsal aspect of L5 DRG, a key region for stimulation applications. To take advantage of this quantitative knowledge of DRG organization, future neural interfaces with DRG will require more advanced technologies. Standard silicon-based electrode arrays, while useful for short-term DRG recordings, ultimately fail in chronic use after several weeks as a result of mechanical mismatch with neural tissue. In this thesis, I demonstrate sensory recording from the surface and interior of sacral DRG during acute surgery using a variety of flexible polyimide microelectrode arrays 4-μm thick and minimum site separation 25 to 40 μm. Using these arrays, I recorded from bladder and somatic afferents with high fidelity. The high density of sites allowed for neural source localization from surface recordings to depths 25 to 107 µm. This finding supports the anatomical analysis suggesting a high density of cell bodies in the dorsal surface region where the surface array was applied. The high site density also allowed for the use of advanced signal processing to decrease analysis time and track neural sources during movement of the array which may occur during future behavioral experiments. This thesis represents significant advances in our understanding of DRG and how to interface with them, particularly related to the way anatomy can inform development of future technologies. Going forward, it will be important to expand the anatomical maps based on organ function and to test the novel flexible arrays in chronic implant experiments.PHDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/153477/1/zsperry_1.pd