High density microelectrode arrays for in vitro retinal studies

[摘要] Neurophysiologists traditionally studied the behaviour of individual neurons by measuring their extracellular signalling on a single electrode. This PhD has involved developing a technology to enable the behaviour of populations of neurons in the retina to be studied. By recording simultaneously from hundreds of neurons a much greater insight into retinal processing and encoding is achievable. To this end, a large area, high density, transparent microelectrode array, of unprecedented dimensions, was manufactured on a glass/indium tin oxide (ITO) substrate. This state-of-the-art device has 519 hexagonally close-packed, 5 mum diameter electrodes spaced by 30 mum. Al-1 channels are electrically well isolated with typical interchannel resistance and capacitance values of ~200 GO and 1 pF respectively. Electrodes are electroplated with platinum to form a low impedance (200 kO at 1 kHz) interface between the electrodes and electrolyte. Fabrication and modelling tests also proved the electrical and physical feasibility of future larger area and higher density arrays. Investigations were carried out to establish an electrode/electrolyte interface capable of delivering enough charge to directly stimulate neurons in the retina. Iridium oxide films formed by an electrochemical activation technique were found to create 5 mum diameter electrodes with 4 mC/cm2 charge capacity and 150 kO (at 1 kHz) impedance which are ideal characteristics for direct electrical stimulation of neurons. The state-of-the-art microelectrode array technology developed in this thesis has allowed amongst the most complete datasets from primate retina to be produced.

[发布机构] University:University of Glasgow

[关键词] Biomedical engineering, Electrical engineering