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Wire electronics and woven logic, as a potential technology for neuroelectronic implants
KTH, School of Technology and Health (STH), Neuronic Engineering. (Neuronik)
(Biomolecular and Organic Electronics)
(Image coding)
(Biomolecular and organic electronics)
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(English)Manuscript (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.

Keyword [en]
conducting polymers, functional electrical stimulation, textile electronics
National Category
Other Engineering and Technologies not elsewhere specified
URN: urn:nbn:se:kth:diva-9847OAI: diva2:133571
QC 20100623Available from: 2009-01-12 Created: 2009-01-12 Last updated: 2010-07-19Bibliographically approved
In thesis
1. Conjugated Polymers for Neural Interfaces: Prospects, possibilities and future challenges
Open this publication in new window or tab >>Conjugated Polymers for Neural Interfaces: Prospects, possibilities and future challenges
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Within the field of neuroprosthetics the possibility to use implanted electrodes for communication with the nervous system is explored. Much effort is put into the material aspects of the electrode implant to increase charge injection capacity, suppress foreign body response and build micro sized electrode arrays allowing close contact with neurons. Conducting polymers, in particular poly(3,4-ethylene dioxythiophene) (PEDOT), have been suggested as materials highly interesting for such neural communication electrodes. The possibility to tailor the material both mechanically and biochemically to suit specific applications, is a substantial benefit with polymers when compared to metals. PEDOT also have hybrid charge transfer properties, including both electronic and ionic conduction, which allow for highly efficient charge injection.


Part of this thesis describes a method of tailoring PEDOT through exchanging the counter ion used in electropolymerisation process. Commonly used surfactants can thereby be excluded and instead, different biomolecules can be incorporated into the polymer. The electrochemical characteristics of the polymer film depend on the ion. PEDOT electropolymerised with heparin was here determined to have the most advantageous properties. In vitro methods were applied to confirm non-cytotoxicity of the formed PEDOT:biomolecular composites. In addition, biocompatibility was affirmed for PEDOT:heparin by evaluation of inflammatory response and neuron density when implanted in rodent cortex.


One advantage with PEDOT often stated, is its high stability compared to other conducting polymers. A battery of tests simulating the biological environment was therefore applied to investigate this stability, and especially the influence of the incorporated heparin. These tests showed that there was a decline in the electroactivity of PEDOT over time. This also applied in phosphate buffered saline at body temperature and in the absence of other stressors. The time course of degradation also differed depending on whether the counter ion was the surfactant polystyrene sulphonate or heparin, with a slightly better stability for the former.


One possibility with PEDOT, often overlooked for biological applications, is the use of its semi conducting properties in order to include logic functions in the implant. This thesis presents the concept of using PEDOT electrochemical transistors to construct textile electrode arrays with in-built multiplexing. Using the electrolyte mediated interaction between adjacent PEDOT coated fibres to switch the polymer coat between conducting and non conducting states, then transistor function can be included in the conducting textile. Analogue circuit simulations based on experimentally found transistor characteristics proved the feasibility of these textile arrays. Developments of better polymer coatings, electrolytes and encapsulation techniques for this technology, were also identified to be essential steps in order to make these devices truly useful.


In summary, this work shows the potential of PEDOT to improve neural interfaces in several ways. Some weaknesses of the polymer and the polymer electronics are presented and this, together with the epidemiological data, should point in the direction for future studies within this field.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. vi, 77 p.
Trita-STH : report, ISSN 1653-3836 ; 2009:1
neuroprosthetics, conjugated polymers, conducting polymers, PEDOT, functional electrical stimulation, neural electrodes
National Category
Medical Laboratory and Measurements Technologies Neurosciences Other Materials Engineering
urn:nbn:se:kth:diva-9817 (URN)978-91-7415-213-5 (ISBN)
Public defence
2009-01-30, Sal 3-221, Alfred Nobels Allé 10, Huddinge, 13:00 (English)
QC 20100623Available from: 2009-01-13 Created: 2009-01-09 Last updated: 2010-06-23Bibliographically approved

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Asplund, Mariavon Holst, Hans
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