**1. Introduction**

In-home physiological monitoring, also known as remote patient monitoring, enables long-term tracking of patients' health from the comfort of their homes without the need to visit a clinic. It has the potential to facilitate a healthcare transformation from reactive to proactive preventive care. In-home physiological monitoring of biopotential (voltage) signals such as an Electroencephalogram (EEG), Electrocardiogram (ECG), and Electromyogram (EMG) enables tracking daily changes in a patient's health [1]. The current state of the art for in-home monitoring is inclined

towards non-invasive technologies such as wearable mobile devices and patch-based sensors (**Figure 1**). In both technologies a biopotential electrode picks up voltage signals from the surface of the body and acts as an interface between the tissue and the electronics.

This chapter is focused on the mechanism of *dry electrodes*, but we include here a brief description of the most common type of biopotential electrode, the *wet electrode*. A wet electrode is an electrochemical electrode and consists of two major parts: the metal plate and the electrolyte. An example of a wet electrode is an ECG disposable electrode commonly used in clinical settings. It consists of an electrochemically active gel (this acts as an electrolyte and contains conductive ions), which is in direct contact with both the skin and the metallic part of the electrode, the inside of which is coated with Ag/AgCl and the outside is connected to a metal snap. The whole assembly is mounted on a flexible foam pad and contains adhesive for ease of attachment to the body. Due to the adhesive, wet electrodes stay in contact with the skin while the person is moving and can compensate for the motion artifacts. However, there are certain drawbacks of using the wet electrodes: the skin needs to be prepared by a skilled person; the gel dries over time, leading to signal degradation; and the removal of the gel electrodes is often painful or leads to skin irritation.

To overcome the limitations of wet electrodes, dry electrodes are being integrated into wearable devices such as watches and hand-held monitoring devices thus making them user-friendly. The mechanistic principle involved in the functioning of dry electrodes is important to understand and is different from that of wet electrodes, and is discussed in Section 2. Based upon this mechanistic principle, this chapter provides a brief overview of different types of dry electrodes that exist in the literature. Factors such as the electrode area, material, applied pressure, and skin hydration that affect the electrode performance are presented in Section 3. This is followed by a discussion of the existing methods for testing the performance of these electrodes in Section 4. Finally, the chapter summarizes the key findings about the factors that affect electrode performance along with suggestions for future directions to aid wearable electrode development.

#### **Figure 1.**

*Biopotential signals acquisition such as electroencephalogram (EEG), electrocardiogram (ECG), and electromyogram (EMG) using wearable electrodes on the skin.*

*Factors Affecting Wearable Electrode Performance and Development of Biomimetic Skin… DOI: http://dx.doi.org/10.5772/intechopen.111429*
