# Experimental Demonstration of Single-Channel EEG Signal Using 32 x 32 Pixel OLED Screen and Camera
## 2 Related Works
### Current EEG Procedure in Hospitals and RF-Based EEG Products  
The current EEG procedure in hospitals involved deployed wet electrodes, thus resulting in long preparation time, which was not only tedious and time consuming but also resulted in discomfort to patients [23]. In context, to overcome the problem of wet electrodes, several researchers moved to dry electrodes for EEG brain monitoring. The authors in [24] mentioned that, in comparison to traditional EEG brain monitoring, existing EEG wireless devices deploy dry electrodes; however, a direct link between the scalp and electrodes is prevented by hair, thus resulting the path being obstructed in EEG signal measurement. Usually, the conventional silver-silver chloride electrodes with conductive gels were used to record EEG; however, conductive gels can dry and become hard over long-term EEG monitoring. Therefore, the EEG signal captured is not accurate due to there being no proper contact between the scalp and the electrode [25]. In [26], the authors proposed a comb-shaped electrode, whereby the hair could be easily moved, hence the electrode could easily reach the scalp, thus providing accurate EEG monitoring. However, it was only deployed in brain computer applications. The authors in [27] employed metal pogo probes for brain monitoring; despite high precision the dry sensors caused discomfort to users after several hours. The single-channel EEG monitoring was proposed by authors in [28], using Bluetooth technology to transmit data wireless whereby the single cylindrically-shaped electrode was used for brain monitoring. However, RF technology using systems like Bluetooth and Zigbee for wireless transmission affect system performance in RF sensitive areas, such as hospitals, aircrafts, etc., due to electromagnetic interference. The authors in [29] deployed in-ear sensors for brain monitoring; however, despite of the low-input impedance of the sensors, were unable to provide a comprehensive study of the brain. The pathway between a computer device and the brain is known as the brain-computer interface (BCI) [30; 31]. Neurosky is most commonly used in BCI and is based on one channel measurement using dry electrodes. It is used to study a specific section or part of the brain [32]. Another most commonly-used EEG product is Emotiv, which provides 12 h continuous wireless transmission through a radio. However, the continuous monitoring for 12 h using RF technology might have adverse effects on patients' health due to electromagnetic interference [33]. The EEG product designed by authors in [34] is G.Nautilus, and is a lightweight device that is preferred for the comprehensive study of the brain due to EEG recordings from several channels. Mindo-4 is another BCI EEG product mainly deployed in gaming applications and to measure sleep disorders, and it has a weight of 250 g and a battery life of 10 h. The dry sensors are preferred in EEG, in comparison to wet sensors, due to the long preparation time of wet sensors and them being uncomfortable for patients [35]. In order to measure the mood in people, Cognonics or Quick 20 is widely used, operating wirelessly at a frequency ranging from 0-131 Hz at 500 samples/s with 64 channels, and at a frequency ranging from 0-262 Hz at 1000 samples/s with 32 channels [36]. Enobio, another EEG wearable system, is preferred for the recording of EEG, which is best for applications such as sleep studies [37]. The applications of EEG devices vary, and the selection of EEG products depends upon the requirement of individual applications with consideration of following key parameters such as sampling rate, resolution, battery life and number of electrodes. For example, for brain monitoring, if the number of channels required is 1, and a bandwidth ranging between 3-100 Hz at a sampling rate of 512 Hz and battery life of 8 h is needed, Neurosky is the best choice [32].