Towards Improving the Quality of Electrophysiological Signal Recordings by Using Microneedle Electrode Arrays

Objective:
Electrophysiological signals are recorded generally by metal electrodes placed on body surface. For long term use, the signal quality may decay with the change of interface impedance between electrodes and skin due to the conductive hydrogel dehydration. Besides, electrodes may shift during body movements, which causes unstable signal recordings.
Methods:
To improve the quality of electrophysiological signal recordings on human body surface, a type of microneedle electrode array (MEA) with microneedles around 550 μm in length was fabricated with a magnetization-induce self-assembly method.
Results:
Compared with the commonly used dry electrode array, the MEA has lower and more stable interface impedance, especially when the electrode-skin interface is under unstable pressures. For electrophysiological signal recording, the MEA can acquire electromyography (EMG) with significantly lower noise energy, higher signal-to-noise ratio, and higher motion-classification accuracy based on the EMG pattern-recognition method. Additionally, high quality electrocardiography (ECG) can be recorded by using the MEA, where more accurate R-peaks are extracted in different scenarios. Besides, there was no report about any discomfort like bleeding or inflammation by all the subjects.
Conclusion:
This research proved that the microneedles on the MEA can penetrate through the corneum and reach the epidermis of the subjects, which could avoid the influence of corneum and fix the electrode on the body surface for high-quality signal recording especially during body movements. Furthermore, the microneedles would not touch the dermis, enabling a painless signal acquisition.
Significance:
This work is beneficial to the applications of wearable human-machine interface technology.