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  • 1.
    Asplund, Maria
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Hamedi, Mahiar
    Forchheimer, Robert
    Inganäs, Olle
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Wire electronics and woven logic, as a potential technology for neuroelectronic implantsManuscript (Other (popular science, discussion, etc.))
    Abstract [en]

    New strategies to improve neuron coupling to neuroelectronic implants are needed. In particular, to maintain functional coupling between implant and neurons, foreign body response like encapsulation must me minimized. Apart from modifying materials to mitigate encapsulation it has been shown that with extremely thin structures, encapsulation will be less pronounced. We here utilize wire electrochemical transistors (WECTs) using conducting polymer coated fibers. Monofilaments down to 10 μm can be successfully coated and weaved into complex networks with built in logic functions, so called textile logic. Such systems can control signal patterns at a large number of electrode terminals from a few addressing fibres. Not only is fibre size in the range where less encapsulation is expected but textiles are known to make successful implants because of their soft and flexible mechanical properties. Further, textile fabrication provides versatility and even three dimensional networks are possible. Three possible architectures for neuroelectronic systems are discussed. WECTs are sensitive to dehydration and materials for better durability or improved encapsulation is needed for stable performance in biological environments.

  • 2.
    Asplund, Maria
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Thaning, Elin
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Lundberg, Johan
    Sandberg-Nordqvist, Ann-Christin
    Kostyszyn, Beata
    Inganäs, Olle
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Biocompatibility of PEDOT/biomolecular composites intended for neural communication electrodesManuscript (Other (popular science, discussion, etc.))
    Abstract [en]

    Electrodes of the conjugated polymer poly(3,4-ethylene dioxythiophene) (PEDOT) have been shown to possess very attractive electrochemical properties for functional electrical stimulation (FES) or recording in the nervous system. Biomolecules already present in nervous tissue, added as counter ions in PEDOT electropolymerisation, could be a route to further improve the biomaterial properties of PEDOT, eliminating the need of surfactant counter ions like docedyl benzene sulphonate (DBS) or polystyrene sulphonate (PSS) in the polymerisation process. Such PEDOT/biomolecular composites using heparin, or hyaluronic acid, have been electrochemically investigated in a previous study and have been shown to retain the attractive electrochemical properties already proven for PEDOT:PSS.

     

    The aim of the present study is to evaluate biocompatibility of these PEDOT/biomolecular composites in vitro and also evaluate PEDOT:heparin biocompatibility in cortical tissue in vivo. Hereby, we also aim to identify a suitable test protocol, that can be used in future evaluations when further material developments are made.

     

    Material toxicity was first tested on cell lines, both through a standardised agarose overlay assay on L929 fibroblasts, and through elution tests on human neuroblastoma SH-SY5Y cells. Subsequently, a biocompatibility in vivo test was performed using PEDOT:heparin coated platinum probes implanted in the cerebral cortex of Sprague-Dawley rats. Tissue was collected at three weeks and six weeks of implantation and evaluated by immunohistochemistry.

     

    No cytotoxic response was seen to any of the PEDOT:biomolecular composites tested here. Furthermore, elution tests were found to be a practical and effective way of screening materials for toxicity and had a clear advantage over the agarose overlay assay, which was difficult to apply on other cell types than fibroblasts. Elution tests would therefore be recommendable as a screening method, at all stages of material development. In the in vivo tests, the stiffness of the platinum substrate was a significant problem, and extensive glial scarring was seen in most cases irrespective of implant material. However, quantification of immunological response through distance measurements from implant site to closest neuron, and counting of macrophage densities in proximity to polymer surface, was comparable to those of platinum controls. These results indicate that PEDOT:heparin surfaces were as compatible with cortical tissue as pure platinum controls.

  • 3.
    Thaning, Elin
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Asplund, Maria
    KTH, School of Technology and Health (STH).
    Nyberg, Tobias
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Inganäs, Olle
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Stability of PEDOT materials intended for implantsManuscript (Other (popular science, discussion, etc.))
    Abstract [en]

    This study presents a set of experiments designed to study the stability over time of the conducting polymer poly(3,4-ethylene dioxythiophene) (PEDOT), under simulated physiological conditions. Especially, the influence of switching the counter ion used in electropolymerisation, from surfactant polystyrene sulphonate (PSS) to heparin, was investigated. Electropolymerised PEDOT was exposed to different solutions at 37 °C over a 5-6 weeks study period. Two methods were used to study changes over time, spectroscopy and cyclic voltammetry. Phosphate buffer solution (PBS) and diluted hydrogen peroxide (H2O2) (0.01 M) were used to simulate in vivo environment. Some PEDOT electrodes in PBS were also subject to voltage pulsing to further stress the material.

     

    The vast part of the samples of both types lost both electroactivity and optical absorbance within the study period, when exposed to H2O2. An overall slightly higher stability of PEDOT:PSS compared to PEDOT:heparin could be seen. The time dependence of the decline also differed, with a linear decrease of electroactivity for PEDOT:heparin while for PEDOT:PSS a comparably stable appearance initially, followed by a marked decrease after 8-15 days.

     

    Polymers were relatively stable in PBS throughout the study period, with around 80% of electroactivity remaining after five weeks. Disregarding a slight drop in electroactivity during the first day, voltage pulsing in PBS did not increase degradation (tested over 11 days). Delamination of PEDOT exposed to PBS was however a significant problem, especially for polymer on ITO substrates.

     

    PEDOT is sensitive to oxidising agents, also in the dilute concentrations used here, and counter ion influences the time course of degradation. Even without oxidising agents, some decline in electroactivity can be expected and it is unclear whether this decrease will continue over time, or if the polymer will stabilise. Such stabilisation was however not seen within the five weeks studied here. Delamination of polymer is likely to be a problem on implantation, especially with unwisely chosen substrates, and might be an even more serious threat to long term applications than degradation in biological fluids.

  • 4.
    von Holst, Hans
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Kleiven, Svein
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Protective Material2010Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A protective material/structure is provided that reduces the risk of injury for a person after contact with said material/structure, and is based on a structure where an inner and outer shell can move relative to each other. The shells are separated by spikes or thin beams and the outer shell covers or envelops the spikes. The spikes or beams are constructed so that they permit displacement of the outer shell relative to the inner shell in the event of an oblique impact against the protective material/structure. The spikes or beams are designed to be thin/slim and can be made of flexible polymer materials such as plastics, rubber or fibers. This enables the spikes to give way after a tangential/rotational impact and thereby efficiently reduce the negative effects of such an impact on the brain. The material/structure can be used in e.g. helmets, vehicle interiors, vehicle exteriors, indoor house building material, boxing gloves and the like.

  • 5.
    von Holst, Hans
    et al.
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Kleiven, Sveinsveink
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Ho, Johnson
    KTH, School of Technology and Health (STH), Neuronic Engineering (Closed 20130701).
    Non-invasive brain injury evaluation2009Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    A non-invasive method for measuring intracranial pressure (ICP) is provided. A numerical model such as finite element model is developed in order to calculate the ICP, strain or stress for patients who suffers from hematoma, edema or tumor. The method can further provide local maximum principle strain that can provide information about possible subsequent brain injury, such as diffuse axonal injury, in sensitive region of the brain. Based on computer tomography or magnetic resonance images an individual diagnosis and treatment plan can be formed for each patient.

    (FR)L'invention concerne un procédé non invasif visant à mesurer la pression intracrânienne (ICP). Un modèle numérique tel qu’un modèle par éléments finis est développé afin de calculer l’ICP, la déformation ou la contrainte pour des patients souffrant d’un hématome, d’un œdème ou d’une tumeur. Le procédé peut en outre fournir le maximum local de déformation principale qui peut donner des informations concernant d’éventuelles lésions cérébrales subséquentes, comme des lésions axonales diffuses, dans une région sensible du cerveau. Sur la base d’une tomographie informatisée ou d’images par résonance magnétique, un diagnostic et un plan de traitement individualisés peuvent être formulés pour chaque patient.

  • 6.
    Wikander, Jan
    et al.
    KTH, School of Industrial Engineering and Management (ITM).
    von Holst, Hans
    KTH, School of Technology and Health (STH), Neuronic Engineering.
    Ingvast, Johan
    Kraftförstärkande handske2006Patent (Other (popular science, discussion, etc.))
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