Abstract
BackgroundConventional ways of making bio-electrodes are generally complicated, expensive and unconformable. Here we describe for the first time the method of applying Ga-based liquid metal ink as drawable electrocardiogram (ECG) electrodes. Such material owns unique merits in both liquid phase conformability and high electrical conductivity, which provides flexible ways for making electrical circuits on skin surface and a prospective substitution of conventional rigid printed circuit boards (PCBs).MethodsFundamental measurements of impedance and polarization voltage of the liquid metal ink were carried out to evaluate its basic electrical properties. Conceptual experiments were performed to draw the alloy as bio-electrodes to acquire ECG signals from both rabbit and human via a wireless module developed on the mobile phone. Further, a typical electrical circuit was drawn in the palm with the ink to demonstrate its potential of implementing more sophisticated skin circuits.ResultsWith an oxide concentration of 0.34%, the resistivity of the liquid metal ink was measured as 44.1 µΩ·cm with quite low reactance in the form of straight line. Its peak polarization voltage with the physiological saline was detected as −0.73 V. The quality of ECG wave detected from the liquid metal electrodes was found as good as that of conventional electrodes, from both rabbit and human experiments. In addition, the circuit drawn with the liquid metal ink in the palm also runs efficiently. When the loop was switched on, all the light emitting diodes (LEDs) were lit and emitted colorful lights.ConclusionsThe liquid metal ink promises unique printable electrical properties as both bio-electrodes and electrical wires. The implemented ECG measurement on biological surface and the successfully run skin circuit demonstrated the conformability and attachment of the liquid metal. The present method is expected to innovate future physiological measurement and biological circuit manufacturing technique in a large extent.
Highlights
Electrocardiogram (ECG) reflects the electrical activity of the heart, which is an essential physiological parameter for both clinical diagnostics and health monitoring
The disposable button electrodes are mainly used in portable ECG monitor devices with electrolytic gel for conduction enhancement and Ag/AgCl as electrode material to pursue better performance [1]
The liquid metal ink was filled in a 40 cm long plastic tube, which has an inner diameter of 1 mm
Summary
Electrocardiogram (ECG) reflects the electrical activity of the heart, which is an essential physiological parameter for both clinical diagnostics and health monitoring. The flat metal electrodes are rigid plates that clamp the limbs and the suction electrodes are small evacuated cups that suck tightly to the skin Both kinds of electrodes are commonly used on the ECG instruments in clinics and hospitals. They usually have poor coupling performance with the skin and high signal noise that has to be overcome with electrolytic gel. We describe for the first time the method of applying Ga-based liquid metal ink as drawable electrocardiogram (ECG) electrodes Such material owns unique merits in both liquid phase conformability and high electrical conductivity, which provides flexible ways for making electrical circuits on skin surface and a prospective substitution of conventional rigid printed circuit boards (PCBs)
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