Recently, a type of silver/silver chloride sintered coating is newly developed by us, it mixes nano-grade silver/silver chloride powder with adhesives and diluents in proper proportion. It could attach to the surface as a new coating layer. Provided with a highly dispersed electrochemical interface, this coating can quickly reach potential equilibrium within 2 minutes, resistance around 0.1KΩ. And the potential drift shows as low as 15uV within 1 minute. It fully meets the requirements of conventional bioelectricity measurement. It is perfectly suitable for the increasing demand for disposable sensor requirements.
Why do electrodes of different materials have different electrical performances?
To put it frankly, the ability of different materials to process electrical signals is different. The electrical signal includes two parts: the balance between the electrode and the solution, and the processing of external signals.
An electrical signal (such as epilepsy, stroke signal) comes from the solution, and the electrode needs to convert the ion signal in the solution to an electronic signal that can be received by the end device. There is an interface between ions and electrons.
If a large current signal suddenly comes, or there are too many accumulated signals to be processed, which are over the processing capacity of the electrode, the electrical signals will accumulate in the interface, which is what we commonly call polarization.
The processing capacity of different materials is different, some are fast and some are slow. Among them, sintered silver/silver chloride is the best material.
Tallgrena, S. Vanhataloa,b, K. Kailua, J. Voipioa,*Clinical Neurophysiology 116 (2005) 799–806 Evaluation of commercially available electrodes and gels for the recording of slow EEG potentials.
Then, When the electrode first contacts the solution, it needs to reach the ionization balance of the electrode-solution interface. Generally speaking, it takes abt 30 minutes for this process to stabilize.
We can use an activation method to help the electrode reach the balance in advance so that the electrode-solution interface balance time can be speeded up during use. However, the electrode will slowly return to its original state during the storage period, and it will still take time to reach the best ionization balance after contacting the solution (It can be noted that almost all the methods for measuring the performance of the electrode on the market are placed twenty or thirty minutes later).
The sintered AgCl electrode is a microporous structure under SEM images, which greatly increases the processing capacity of electrical signals, not just the silver chloride-coating surface.
(Microstructure under the electron microscope of silver/silver chloride powder sintered electrode)
Theoretically, the sintered AgCl electrode also needs to reach electrode-solution balance, even if it is unbalanced, it is more than enough when processing routine electrical signals, and it will be better after balance. It is generally used for high-quality requirement scientific research, where the signal quality requirements are particularly high.
In summary, the sintered AgCl coating electrodes and old coated AgCl electrodes have fundamental changes in terms of electrode materials. It is suitable for the high-quality requirement disposable sensor requirement, which needs equal signal quality as-sintered AgCl but has limited control of material cost.