Researches On Flexible Electrocardiogram Electrode Prepared By Coating Method And Its Performance

The importance of heart state for human health is self-evident,heart rate and electrocardiogram（ECG）are the most important parameters to evaluate the state of heart health,timely monitoring of heart activity will effectively prevent cardiovascular disease emergencies,so portable heart health monitoring instruments show great commercial value.Traditional ECG machines have the characteristics of large size,complex connection methods,and the rejection of Ag/Ag Cl gel electrodes with the skin,all of which have prompted researchers to conduct extensive research on new flexible ECG electrodes,high-precision ECG signal acquisition circuits,and ECG noise filtering algorithms.In this thesis,a new flexible electrode fabrication method was adopted,the highly conductive electronic Ag ink mixture was directly applied to the surface of the skin to form an ultra-thin electrode pattern.Choosing the method of direct coating with a pen can obtain an electrode film with a uniform thickness of 15 μm,and the 10% tensile test of the coated electrode pattern is performed 300 times,still maintaining a sufficiently high conductivity.Electronic Ag ink material stored at room temperature for 30 days still shows a stable electrical response.Skin-electrode impedance testing shows that the impedance value of the coated electrode in a steady state is 49 kΩ,which is very close to that of commercial gel electrode,and the coated electrode shows good stability in dynamic impedance testing,while the metal Cu electrode manifests great motion interference due to its hard surface.The ECG monitoring system use the ADS1292 R biopotential sensing chip to achieve high-precision ECG signal acquisition,and the common mode rejection ratio（CMRR）under the default condition of the overall system is 112 d B,which realizes the signal differential amplification output.Ambient noise is easy to introduce 50 Hz power frequency noise in the test system,fast fourier transform（FFT）spectrum analyses show that the ECG signal noise range is mainly concentrated in the 0-0.5 Hz and greater than40 Hz frequency ranges.The FIR digital filter based on MATLAB obtains accurate 161-order filter coefficients,and the signal-to-noise ratio（SNR）of the ECG signal preprocessed by the digital filter is 26.77 d B.The performance of the coated flexible electrode was comprehensively tested by using portable ECG monitoring system and digital filter.In the static test,the coated electrode and the single-cycle ECG signal of the Ag/Ag Cl electrode almost coincided,Electrocardiogram obtained with coated electrode has better wave characteristics.Noise interference occur in the ECG test results of four different movement states,the bandpass filtering results of the disturbed signal show a uniform QRS wave,the coating electrode can be used to achieve stable heart rate monitoring.In the continuous monitoring experiment of the coated electrode for 24 hours,the ECG signal did not decay,and the SNR slightly increased.The signal-to-noise ratio of the electrocardiogram obtained by the coated electrode during the test is higher than that of the commercial Ag/Ag Cl electrode.The above results show that the coated electrode can be suitable for ECG monitoring in many occasions.