Design and fabrication of an inflation-activated FPCB MEMS-based electrode for bio-signal recording with an in-canal fixation capability

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Ranjbar, Ehsan
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This research aims to propose a design and fabrication process for a novel miniaturized electrode which can be potentially exploited to record EVestG signals and ear electrical activity from the middle inner parts, including semicircular canals and otolith organs, by an extra-tympanic electrode. This thesis covers EVestG signal recording, its currently used electrode, and the associated current challenges, followed by a review of micro-fabrication techniques, including Micro Electro Mechanical Systems (MEMS) conventional fabrication techniques (sputtering), 3Dprinting micro-fabrication technologies (Stereo-lithography or SLA), and Bio-MEMS electrode fabrication for new electrodes design with their associated technical challenges. It also presents some methodologies to cope with the challenges in our design, studying their feasibility. Then, it adopts one of the presented methodologies, which seem more feasible regarding our accessible facilities and resources. The methodology was chosen for a new needle-electrode design (potentially for EVestG recording) and it was fabricated using various technologies such as air-actuation using medical balloons, Flexible Printed Circuit Board (FPCB), 3D-printing, and MEMS fabrication. The fabrication process, from basic steps to the latest developments, is reported illustratively. Finally, the performance of the designed and fabricated micro-needle electrodes from impedance against pressure variation is investigated via some in-vitro experiments. The experiments demonstrate impedance reduction of the fabricated plastic silver-sputtered SLA-3D-printed micro-needle electrodes as the pressure increases.
FPCB, MEMS, Bioelectrode, Inflation, Pressure - activated, Impedance reduction, In-canal fixation, Miconeedle, Copper/silver ball-tip, Cotton-wool tip, Medical balloon, Additive manufacturing, Sputtering, SLA/FDM 3D-printing, Conductive silver epoxy/glue/paint