Dry electrode solution

Category: Brain-computer interface

Time：2024-12-21

With the rapid advancement of technologies such as neuroscience, artificial intelligence, chips, and algorithms, non-invasive brain-computer interfaces (BCIs) have also made significant progress in recent years. Thanks to their advantages of real-time interaction and high accuracy, BCIs have demonstrated unique application value in a variety of fields, including medical rehabilitation, sleep monitoring, driving assistance, and brain-controlled typing.

Non-invasive brain-computer interface electrodes are generally categorized into two major types: wet electrodes and dry electrodes. Traditional wet-electrode technology requires the use of a syringe equipped with a needle to inject gel onto the subject, thereby reducing the contact impedance between the electrode and the scalp. The wearing process is cumbersome and time-consuming, and as the conductive gel evaporates, the signal quality deteriorates, making it impossible to achieve stable data acquisition over extended periods.

Dry electrode technology does not rely on conductive pastes, making it convenient to use and enabling long-term continuous signal acquisition. Common types of dry electrodes include skin-patch dry electrodes, microneedle dry electrodes, and metal-pillar dry electrodes. Although innovations in materials and manufacturing processes have significantly improved the performance of skin-patch and microneedle dry electrodes, they still face certain limitations in application scenarios due to their inability to overcome hair obstruction. On the other hand, metal-pillar dry electrodes, with their relatively rigid texture, tend to cause greater pressure and discomfort during use. As a result, they often require sophisticated mechanical designs—such as helmets or spring-loaded clips—to balance both user comfort and stable electrode contact.

Greentek dry electrodes are designed to enhance wearing comfort. The electrodes are made from a soft, conductive elastomer material that deforms slightly when pressed firmly against the scalp, thereby reducing pressure and discomfort on the scalp. The contact claw-shaped tip area is coated with silver/silver chloride material. Thanks to the inherent low polarization and low-noise characteristics of silver chloride, these electrodes maximize the signal-to-noise ratio of the recorded signals. Additionally, the electrodes feature three different claw lengths, allowing them to better penetrate hair and conform to various head shapes.

Figure 1: The potential difference between a pair of electrodes in the electrolyte for dry electrodes.

Figure 2. AC impedance spectra of a pair of dry-electrode contacts in an electrolyte (10 mV perturbation, 1–10 kHz bandwidth)

Table 3: Performance Parameters of Dry Electrodes

Testing has shown that the BP amplifier (V-amp 16-channel) can essentially meet the functional requirements for EEG signal acquisition. The dry electrodes, paired with blue triangular caps, achieve an electrode-skin impedance greater than 100 kΩ. The acquired EEG waveforms are stable and of high quality, and distinct characteristic waveforms can be observed even during blinking or when the eyes are closed. The electrodes also offer excellent comfort. These dry electrodes are made from a flexible material with moderate hardness, providing good comfort; after wearing them for 1 hour, no significant discomfort was reported.

It should be noted that although dry electrodes can currently acquire EEG signals within a certain range to some extent, since they involve direct contact between an electronic conductor and the skin—with no ion-conducting interface such as conductive gel or saline—they still exhibit very high contact impedance compared to wet electrodes. This high contact impedance tends to introduce greater noise during EEG signal acquisition, thereby degrading the quality of the EEG signals. Typically, it is necessary to employ active electrode technology or advanced algorithms to mitigate the issues of high noise and signal interference inherent in dry-electrode recording.

The previous one

None

Semi-dry EEG electrode solution