354 research outputs found

    Intracortical Neural Probes with Post-Implant Self-Deployed Electrodes for Improved Chronic Stability.

    Full text link
    This thesis presents a new class of implantable intracortical neural probe with small recording electrodes that deploy away from a larger main shank after insertion. This concept is hypothesized to enhance the performance of the electrodes in chronic applications. Today, electrodes that can be implanted into the brain for months or years, are an irreplaceable tool for brain machine interfaces and neuroscience studies. However, these chronically implanted neural probes suffer from continuous loss of signal quality, limiting their utility. Histological studies found a sheath of scar tissue with decreased neural density forming around probe shanks as part of an ongoing chronic inflammation. This was hypothesized to contribute to the deterioration of recorded signals. The neural probes developed in this thesis are designed to deploy electrodes outside this sheath such that they interface with healthier neurons. To achieve this, an actuation mechanism based on starch-hydrogel coated microsprings was integrated into the shank of neural probes. Recording electrodes were positioned at the tip of micrometer fine and flexible needles that were attached to the springs. Before insertion, the hydrogel dehydrates, retracting the springs. After insertion, the gel rehydrates, releasing the springs, which then deploy the electrodes. The actuation mechanism functions in a one-time release fashion, triggered by contact with biological fluids at body temperature. The deployment of the electrodes occurred over the course of two hours and can be divided into three stages: For the first 20 s, the electrodes did not deploy. Within the first three minutes they deployed by roughly 100 µm (0.5 µm/s). Tor the following two hours they deployed an additional 20 µm (0.17 µm/min). The employed design supported six deploying electrodes, each at the end of a 5 µm wide and thick, and 100 µm long needle. These were attached to a shank with 290 µm width, 12 µm thickness and 3 mm length. The shanks could be inserted into the cortex of rats through an opening in the pia without breaking. The acquired waveforms indicate that some of the deployed electrodes were able to record neural action potentials.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/113317/1/egertd_1.pd

    A cardiovascular occlusion method based on the use of a smart hydrogel

    Get PDF
    Smart hydrogels for biomedical applications are highly researched materials. However, integrating them into a device for implantation is difficult. This paper investigates an integrated delivery device designed to deliver an electro-responsive hydrogel to a target location inside a blood vessel with the purpose of creating an occlusion. The paper describes the synthesis and characterization of a Pluronic/methacrylic acid sodium salt electro-responsive hydrogel. Application of an electrical bias decelerates the expansion of the hydrogel. An integrated delivery system was manufactured to deliver the hydrogel to the target location in the body. Ex vivo and in vivo experiments in the carotid artery of sheep were used to validate the concept. The hydrogel was able to completely occlude the blood vessel reducing the blood flow from 245 to 0 ml/min after implantation. Ex vivo experiments showed that the hydrogel was able to withstand physiological blood pressures of > 270 mm·Hg without dislodgement. The results showed that the electro-responsive hydrogel used in this paper can be used to create a long-term occlusion in a blood vessel without any apparent side effects. The delivery system developed is a promising device for the delivery of electro-responsive hydrogels

    Technological challenges in the development of optogenetic closed-loop therapy approaches in epilepsy and related network disorders of the brain

    Get PDF
    Epilepsy is a chronic, neurological disorder affecting millions of people every year. The current available pharmacological and surgical treatments are lacking in overall efficacy and cause side-effects like cognitive impairment, depression, tremor, abnormal liver and kidney function. In recent years, the application of optogenetic implants have shown promise to target aberrant neuronal circuits in epilepsy with the advantage of both high spatial and temporal resolution and high cell-specificity, a feature that could tackle both the efficacy and side-effect problems in epilepsy treatment. Optrodes consist of electrodes to record local field potentials and an optical component to modulate neurons via activation of opsin expressed by these neurons. The goal of optogenetics in epilepsy is to interrupt seizure activity in its earliest state, providing a so-called closed-loop therapeutic intervention. The chronic implantation in vivo poses specific demands for the engineering of therapeutic optrodes. Enzymatic degradation and glial encapsulation of implants may compromise long-term recording and sufficient illumination of the opsin-expressing neural tissue. Engineering efforts for optimal optrode design have to be directed towards limitation of the foreign body reaction by reducing the implant’s elastic modulus and overall size, while still providing stable long-term recording and large-area illumination, and guaranteeing successful intracerebral implantation. This paper presents an overview of the challenges and recent advances in the field of electrode design, neural-tissue illumination, and neural-probe implantation, with the goal of identifying a suitable candidate to be incorporated in a therapeutic approach for long-term treatment of epilepsy patients

    Skin-Integrated wearable systems and implantable biosensors: a comprehensive review

    Get PDF
    Biosensors devices have attracted the attention of many researchers across the world. They have the capability to solve a large number of analytical problems and challenges. They are future ubiquitous devices for disease diagnosis, monitoring, treatment and health management. This review presents an overview of the biosensors field, highlighting the current research and development of bio-integrated and implanted biosensors. These devices are micro- and nano-fabricated, according to numerous techniques that are adapted in order to offer a suitable mechanical match of the biosensor to the surrounding tissue, and therefore decrease the body’s biological response. For this, most of the skin-integrated and implanted biosensors use a polymer layer as a versatile and flexible structural support, combined with a functional/active material, to generate, transmit and process the obtained signal. A few challenging issues of implantable biosensor devices, as well as strategies to overcome them, are also discussed in this review, including biological response, power supply, and data communication.This research was funded by FCT- FUNDAÇÃO PARA A CIÊNCIA E TECNOLOGIA, grant numbers: PTDC/EMD-EMD/31590/2017 and PTDC/BTM-ORG/28168/2017

    Advances in Assistive Electronic Device Solutions for Urology

    Get PDF
    Recent technology advances have led urology to become one of the leading specialities to utilise novel electronic systems to manage urological ailments. Contemporary bladder management strategies such as urinary catheters can provide a solution but leave the user mentally and physically debilitated. The unique properties of modern electronic devices, i.e., flexibility, stretchability, and biocompatibility, have allowed a plethora of new technologies to emerge. Many novel electronic device solutions in urology have been developed for treating impaired bladder disorders. These disorders include overactive bladder (OAB), underactive bladder (UAB) and other-urinary-affecting disorders (OUAD). This paper reviews common causes and conservative treatment strategies for OAB, UAB and OUAD, discussing the challenges and drawbacks of such treatments. Subsequently, this paper gives insight into clinically approved and research-based electronic advances in urology. Advances in this area cover bladder-stimulation and -monitoring devices, robot-assistive surgery, and bladder and sphincter prosthesis. This study aims to introduce the latest advances in electronic solutions for urology, comparing their advantages and disadvantages, and concluding with open problems for future urological device solutions

    Organic electrode coatings for next-generation neural interfaces

    Get PDF
    Traditional neuronal interfaces utilize metallic electrodes which in recent years have reached a plateau in terms of the ability to provide safe stimulation at high resolution or rather with high densities of microelectrodes with improved spatial selectivity. To achieve higher resolution it has become clear that reducing the size of electrodes is required to enable higher electrode counts from the implant device. The limitations of interfacing electrodes including low charge injection limits, mechanical mismatch and foreign body response can be addressed through the use of organic electrode coatings which typically provide a softer, more roughened surface to enable both improved charge transfer and lower mechanical mismatch with neural tissue. Coating electrodes with conductive polymers or carbon nanotubes offers a substantial increase in charge transfer area compared to conventional platinum electrodes. These organic conductors provide safe electrical stimulation of tissue while avoiding undesirable chemical reactions and cell damage. However, the mechanical properties of conductive polymers are not ideal, as they are quite brittle. Hydrogel polymers present a versatile coating option for electrodes as they can be chemically modified to provide a soft and conductive scaffold. However, the in vivo chronic inflammatory response of these conductive hydrogels remains unknown. A more recent approach proposes tissue engineering the electrode interface through the use of encapsulated neurons within hydrogel coatings. This approach may provide a method for activating tissue at the cellular scale, however, several technological challenges must be addressed to demonstrate feasibility of this innovative idea. The review focuses on the various organic coatings which have been investigated to improve neural interface electrodes

    Polysaccharide Layer-by-Layer Coating for Polyimide-Based Neural Interfaces

    Get PDF
    Implantable flexible neural interfaces (IfNIs) are capable of directly modulating signals of the central and peripheral nervous system by stimulating or recording the action potential. Despite outstanding results in acute experiments on animals and humans, their long-term biocompatibility is hampered by the effects of foreign body reactions that worsen electrical performance and cause tissue damage. We report on the fabrication of a polysaccharide nanostructured thin film as a coating of polyimide (PI)-based IfNIs. The layer-by-layer technique was used to coat the PI surface due to its versatility and ease of manufacturing. Two different LbL deposition techniques were tested and compared: dip coating and spin coating. Morphological and physiochemical characterization showed the presence of a very smooth and nanostructured thin film coating on the PI surface that remarkably enhanced surface hydrophilicity with respect to the bare PI surface for both the deposition techniques. However, spin coating offered more control over the fabrication properties, with the possibility to tune the coating’s physiochemical and morphological properties. Overall, the proposed coating strategies allowed the deposition of a biocompatible nanostructured film onto the PI surface and could represent a valid tool to enhance long-term IfNI biocompatibility by improving tissue/electrode integration

    Carbon Fiber Microelectrode Arrays for Neuroprosthetic and Neuroscience Applications.

    Full text link
    The aim of this work is to develop, validate, and characterize the insertion mechanism, tissue response, and recording longevity of a new high-density carbon fiber microelectrode array. This technology was designed to significantly improve the field of penetrating microelectrodes while simultaneously accommodating the variable needs of both neuroscientists and neural engineers. The first study presents the fabrication and insertion dynamics of a high-density carbon fiber electrode array using a dual sided printed circuit board platform. The use of this platform has pushed electrode density to limits not seen in other works. This necessitated the use of an encapsulation method that served to temporarily stiffen the fibers during insertion, but did not enter the brain as many other shuttles do for other probe designs. The initial findings in this work informed the development of an even higher density array using a silicon support structure as a backbone. The second study reports on the tissue reaction of chronically implanted carbon fiber electrode arrays as compared to silicon electrodes. Due to their smaller footprint, the reactive response to carbon fibers should be greatly attenuated, if not non-existent. Results show a scarring response to the implanted silicon electrode with elevated astrocyte and microglia activity coupled to a local decrease in neuronal density. The area implanted with the carbon fiber electrodes showed a varied response, from no detectable increase in astrocytic or microglial activity to an elevated activation of both cell types, but with no detectable scars. Neuronal density in the carbon fiber implant region was unaffected. The data demonstrates that the small carbon fiber profile, even in an array configuration, shows an attenuated reactive response with no visible scaring. The final study reports on the viability of chronically implanted high-density carbon fiber arrays as compared to more traditional silicon planar arrays with comparable site sizes. While most new probe technologies or designs are able to demonstrate proof of concept functionality in acute preparations, very few show the ability to record chronic unit activity. This study aims to provide a comprehensive analysis of electrophysiology data collected over implant durations ranging from 3 – 5 months.PhDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111557/1/parasp_1.pd
    • …
    corecore