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B2: Multielectrode arrays with adjustable stiffness

Thomas StieglitzX, Jürgen RüheF, N.N.


X = Biomedical Microtechnology
F = Inst. Microsystems Technology, Chemistry & Physics of Interfaces


Scientific background

Penetrating electrodes to record single unit spiking activity in the central nervous system are realized as metal wires made with precision mechanics or as silicon-based, micromachined devices, used as single shafts or bundled in arrays. Manufacturing technology and mechanical properties limit minimal shaft size due to fragility and electrical resistance. Electrodes can only be inserted into the tissue in parallel to the needle axis. Therefore, a minimum critical stiffness is necessary. These electrodes are not flexible and cannot adapt to curvature of anatomical structures and pulsatile changes of position. Research focusses on different strategies to improve the tissue-material interface: geometrical variations like lattices structures, tubular substrates with resorbable cores, surface modifications, and hydrogel coatings on stiff substrates. However, with these state of the art developments the basic problems in penetrating microelectrodes are not solved. Mechanical mismatch of the brain-material interface (Eprobes ~160 GPa, Ebrain~10-100 kPa) in combination with the micromotions induces extensive scar formation around the electrodes, resulting in low nerve signal recording amplitudes.


Objectives

We will develop novel concepts for penetrating multichannel microelectrodes in which the mechanical stiffness can be adjusted to match the different requirements during insertion and chronic recording in contact with brain tissue. Thin film electrodes and insulated interconnects will be generated on flexible substrates which are surrounded by a stiff carrier material that allows insertion, and that slowly degrades or softens in the tissue, respectively.

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