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Research On Wearable MEMS Electrodes Sensing Technology For Long-term Biopotential Recording

Posted on:2017-02-10Degree:DoctorType:Dissertation
Country:ChinaCandidate:H L PengFull Text:PDF
GTID:1368330590955512Subject:Electronic Science and Technology
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The biopotential is widely used in medicine and scientific researches because it contains a great deal of information about the human body.With the development of electronic and information technology,more and more applications of biopotentials have been researching.Hence,it is important to record biopotentials ubiquitously.Currently,the wet electrode is widely used to record biopotentials.However,there are some disadvantages of the wet electrode,for example: short time of usage,low spatial density of recording biopotentials.Hence,the wet electrode is unsuitable for ubiquitous biopotential recording.Therefore,it is essential to research the technology of MEMS electrodes for long-term wearable biopotentials recording.According to related literatures at home and abroad,this thesis focused on the technology of MEMS electrodes for long-term wearable biopotentials recording.The main work is as follows:1.The electrode-skin contact impedance of electrodes with different materials was investigated.And then equivalent circuit models of the interface between the dry electrode and the skin were studied,and methods of decreasing electrode-skin contact impedances were investigated.Several types of electrodes were fabricated for this study,and they were fabricated by Au,Cu,conductive polymer composites(PDMS/CNTs),respectively.The area of the dry electrode affects its performances greatly.Therefore the relation between the area and the performance of the dry electrode was studied.In this study nine types of dry metal electrodes with difference areas were fabricated to investigate these influences.2.A qusi-dry electrode(Porous Ti electrode)was developed to solve certain disadvantages of wet and dry electrodes.The disadvantages of wet electrodes contain: short time of usage and low spatial resolution of recording biopentials.The electrode-skin contact impedance of the dry electrode is relatively high.The feasibility of our electrode was proven by experiments of electrode-skin contact impedance measurements and biopotentials recording.3.An Ag/Ag Cl flexible dry electrode with thousands of miniaturized Ag/Ag Cl electrode was developed for biopotentials recording.The effects of the total area and radius of Ag Cl pads on the performances of the flexible dry electrode were investigated.The optimal radius of Ag Cl pad was 50 ?m,and the optimal area ratio between Ag Cl pads and Ag was 38.5%.Our fabricated electrode was flexible and 15?m thick,and these made it comfort to users for long-term and wearable biopotential recording.Moreover,the electrode fitted the skin well,and thus stable contact impedance between the electrode and the skin could be provided during biopotentials recording.The experiments indicated the contact impedance of our flexible dry electrode was lower than that of the conventional flexible dry Ag electrode.Biopotentials recording tests also confirmed that biopotential signals could be acquired perfectly with the fabricated electrode.4.A flexible dry electrode based on conductive polymer composite was developed.Firstly,the high conductive polymer composite was fabricated by dispersing Multi-wall carbon nanotubes(MWCNTs)into Polydimethylsiloxane(PDMS)matrix.The optimal ratio between MWCNTs and PDMS of the composite for the flexible dry electrode was investigated.Secondly,the flexible dry electrode with micropillar array was fabricated by MEMS.The electrode-skin contact impedance was measured in time and frequency domain.The testing result showed that the electrode-skin contact impedance was stable in long-term and low due to the micropillar array of the electrode.Finally,ECG signals were recorded by our electrodes with subjects at resting and walking.The testing results showed that good quality signals were recorded by our electrode and it could reduce motion artifacts effectively.5.A set of wearable biopotential recording system was developed.The system was developed based on the ADS1299,which is the professional chip for biopotential recording.The system could record ECG and EEG successfully with our fabricated electrodes.
Keywords/Search Tags:MEMS, biopotentail recording, dry electrode, long-term, flexible
PDF Full Text Request
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