Abstract
Highly reliable signal recording with low electrode-skin impedance makes the microneedle array electrode (MAE) a promising candidate for biosignal sensing. However, when used in long-term health monitoring for some incidental diseases, flexible microneedles with perfectly skin-tight fit substrates lead to sweat accumulation inside, which will not only affect the signal output but also trigger some skin allergic reactions. In this paper, a flexible MAE on a Miura-ori structured substrate is proposed and fabricated with two-directional in-plane bendability. The results from the comparison tests show enhanced performance in terms of (1) the device reliability by resisting peeling off of the metal layer from the substrate during the operation and (2) air ventilation, achieved from the air-circulating channels, to remove sweat. Bio-signal recordings of electrocardiography (ECG), as well as electromyography (EMG) of the biceps brachii, in both static and dynamic states, are successfully demonstrated with superior accuracy and long-term stability, demonstrating the great potential in health monitoring applications.
Highlights
Stable signal extraction in the long term is an essential part of what makes an electrode suitable for biosignal recording
We describe a novel low-cost and highvolume production compatible fabrication method combining high-precision machining and PDMS mold pressing together to directly form the microlevel needle tips with the macrolevel Miura-ori substrates
To functionalize its electrode conductivity, the sample was coated with 50 nm titanium and 200 nm gold metal layers to ensure its conductivity
Summary
Stable signal extraction in the long term is an essential part of what makes an electrode suitable for biosignal recording. In the early diagnosis of heart disease, ECG is the standard diagnostic method for monitoring ventricular contraction and relaxation. During this test, conventional wet Ag/AgCl electrodes are placed on the patients’ chest. For most cases, the abnormal pulse does not appear on the record sheet during this 1-min test, and it is necessary to have longterm monitoring in home care In this case, wet Ag/AgCl electrodes are no longer suitable since the electrolytic gel on top of the electrodes will increase the electrode-skin interface impedance (EII) as it gradually becomes dry and block sweat evaporation and affect signal acquisition[1]. Some substitutes have been proposed by researchers, such as dry electrodes (DEs) or
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