Advancements in Electrodes for Wearable Skin Devices

By Muhammad OsamaReviewed by Susha Cheriyedath, M.Sc.Apr 20 2024

In a recent review article published in the journal Communications Material, researchers from the Republic of Korea explored the various properties and design strategies of electrodes for wearable skin devices, which are extensively utilized for their ability to provide safe health monitoring.

They discussed the electrical, mechanical, and biocompatible factors affecting the performance of the device electrodes and the current approaches to optimize them. Additionally, they highlighted the potential applications of wearable skin devices in artificial intelligence (AI) and hybrid systems.

Background

Wearable skin devices represent an innovative field in bioelectronics, aiming to seamlessly integrate electronic systems with the human skin for various applications, including vital sign monitoring, biomarker sensing, and enhancing human-machine interfaces. A critical aspect of these devices’ performance is the quality of the electrodes, which interface with the skin to capture or deliver electrical signals. These electrodes serve diverse functions, ranging from providing haptic feedback to electrical muscle or neural stimulation.

Depending on the specific sensor type or application electrodes can take various forms. However, designing electrodes for wearable skin devices presents various challenges due to the skin's elasticity, low modulus, sweat secretion, electrical resistance, and microstructures. Therefore, thorough investigation and optimization of electrode conditions are important to ensure the efficacy and reliability of wearable skin devices.

About the Research

In this review, the authors comprehensively explored how to make high-quality electrodes for wearable skin devices. They discussed the essential characteristics that electrodes should possess, including mechanical properties tied to skin elasticity, electrical properties crucial for device efficacy/performance, and biocompatibility requisites essential for seamless skin-electrode interaction. They emphasized the importance of flexibility to match the skin's movement, conductivity for optimal device performance, and safety to prevent any harm to the skin are foundational features these electrodes must possess.

Next, the study presented different methods to achieve these desired characteristics. This included changing the structure of the electrodes, creating new types of electrodes that are soft and can bend easily, and combining different materials to make hybrid versions. Incorporating AI and multiple functions into these devices was also suggested to make them smarter and more versatile.

Additionally, the researchers provided insight into possible future applications of wearable skin devices. They highlighted applications like monitoring health conditions, diagnosing illnesses, providing treatments, and improving interactions between humans and machines. By exploring these possibilities, the significance of enhancing electrode design was emphasized to optimize the performance of wearable skin devices and pave the way for innovative advancements in healthcare and technology integration.

Research Findings

The paper effectively summarized the current state-of-the-art materials and structures used for wearable skin device electrodes, along with their advantages and limitations. It highlighted the following key outcomes:

Mechanical properties: The electrodes need to exhibit high flexibility, adhesion, and conformability to the skin, achievable through using low-modulus materials, microstructures, or hybrid structures. These properties could enable electrodes to adapt to the skin’s shape and movement, maintaining stable contact and signal quality.

Electrical properties: The electrodes need to have low impedance and high signal-to-noise ratio, attainable with conductive materials, surface coatings, or hydrogels. These properties could facilitate efficient current transfer and high-quality signal acquisition or stimulation.

Biocompatibility: The electrodes must be compatible with the skin and avoid causing irritation, inflammation, or infection. This could be achieved with biologically inert metals, biocompatible polymers, or capacitive electrodes, ensuring safe and long-term skin application.

Additional properties: The electrodes may also require additional properties, such as breathability, transparency, size, and density, depending on the purpose and location of the device. These properties would offer the electrodes the ability to provide comfort, durability, and functionality to the wearer.

Applications

The authors highlighted some potential applications of wearable skin devices that can benefit from advancements in electrode materials and structures:

Health monitoring: These devices can monitor vital signs such as heart rate, blood pressure, temperature, and oxygen saturation, as well as biomarkers like glucose, lactate, and cortisol in body fluids. They provide real-time and continuous feedback to the wearer or medical staff, alerting them to any abnormal conditions or risks.

Diagnosis: They can diagnose various diseases or disorders such as cardiovascular diseases, neurological disorders, skin cancers, and infections by analyzing electrophysiological or biochemical signals from the skin. This capability offers accurate and non-invasive diagnosis, reducing the need for invasive procedures or laboratory tests.

Therapy: These devices can deliver various forms of therapy, including electrical stimulation, drug delivery, wound healing, or gene therapy, to the skin or underlying tissues. They provide personalized and controlled therapy, enhancing treatment efficacy and safety.

Human-machine interfaces: They can create interactive interfaces between humans and machines, such as virtual reality, augmented reality, gaming, or prosthetics. These devices offer sensory feedback like touch, temperature, or pain to the wearer, enabling intuitive and immersive communication with the machine.

Conclusion

The research summarized that wearable skin devices are rapidly evolving and offer great potential for improving human health and well-being. Moving forward, the researchers suggested that further work is needed to overcome the existing challenges and limitations, such as device durability, reliability, scalability, and integration. They proposed that the future of wearable skin devices lies in the combination of AI and hybrid functionalities, which can enable smart devices that can sense, process, and respond to the wearer’s needs. They also anticipate that wearable skin devices will open up new possibilities for human-machine interaction and create novel applications that can enhance the quality of life of the wearer.