| With the continuous improvement of wearable technology,health monitoring has not only uesed in hospital,but also used at home and outdoors.Wearable technology can provide users with personalized long-term health monitoring.Since wet electrodes are not suitable for long-term contact with skin,which may lead to skin irritation and other allergic reactions.Therefor Holter monitor can only continuously work for three days.On the other hand,most of the dry electrode select metal materials,but metal is easy to be corroded,polarized and susceptible to interference and noise.Fabric electrodes have obvious advantages in solving long-term physiological detection.However,the practical application of flexible sensing research also faces severe theoretical and technical challenges.Detecting ECG(Electrocardiogram,ECG)in people's daily life,body motion may cause the fabric electrode to slide,deform and fall off,that leading to "movement artifacts",and affecting the quality of ECG signal.The factors such as material and processe,structure and thickness,size and shape of electrode affect the quality of ECG signal.In this dissertation,we explored the related technology of wearable fabric ECG electrodes for health monitoring.The main work and innovations as fellow:(1)Suppression of motion artifacts fabric electrode structure,fabric electrodes ECG testing of different materials and processWe analyzed the mechanical,electrical and structural properties of electronic fabrics,and summarized the main factors affecting the sensing performance of flexible fabric electrodes are electrode material and process,structure and thickness,size and shape.According to the characteristics of fabric electrodes,the principle of ECG electrode acquisition and the main source of motion artifact,we proposed an electrode design with stable structure and good performance,which suppress movement artifacts.We summarized the methods of making flexible fabric electrode,and selected three kinds of materials and processes(conductive cloth,conductive foam and graphene coating)to make fabric electrode.The comparison test of ECG signal acquisition was carried out on these electrodes.The feasibility of using fabric electrode for ECG signal acquisition was verified by the results of the test.The fabric electrode material and technology with excellent performance was selected.(2)Electrode-skin interface equivalent circuit modelIn order to further analyze the electrical properties of fabric electrodes,we used the method of establishing electrode-skin interface equivalent models.First,we analyzed the characteristics of several equivalent models for different types of ECG electrodes.Considering physical and chemical properties of fabric electrodes,two fabric electrodeskin interface equivalent models were established.Then,we tested the fabric electrodeskin interface contact impedance.Finally,the validity of the equivalent circuit evaluated by the results of fitting impedance spectrum and equivalent circuit.(3)Fabric electrodes performance testThe electrode-skin interface contact impedance test reflects that the size of the impedance has an important impact on the quality of ECG signal.Increasing the size of the fabric electrodes can reduce the impedance.Reducing the impedance can improve the quality of ECG signal.In our study,we systematically analyzed the fabric electrodes of different sizes,and used BIOPAC MP150 multi-guided physiologic recorder for ECG signal acquisition of six volunteers.We also used impedance analyzer for skin-electrode interface contact impedance testing.Then,compared the results of the test with the standard ECG test results,and analyzed the effect of fabric electrode size on electrodeskin interface contact impedance and ECG signal.Finally,the impedance spectrum of fabric electrodes of different sizes were fitted with electrode-skin interface equivalent circuit.The parameters of the components in the equivalent circuit model were analyzed,and further verified the validity of the equivalent circuit. |
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