Recent Advances in Stretchable and Permeable Electrodes for Epidermal Electronics

Abstract

Epidermal electronics is an emerging wearable platform that involves attaching deformable forms of devices to the skin. Epidermal electrodes represent a vital component of this technology, as they provide a direct electronic interface with the skin for sensing and stimulation. However, most of the current electrodes are built on non‐permeable elastomer substrates, which can limit their long‐term, continuous operations in a non‐invasive manner. Fortunately, recent advancements in conductive materials and fabrication techniques have enabled high‐performance epidermal electrodes that are comfortable to wear. In order to track the latest progress, this review article first introduces the designs of permeable structures and the preparation of conductive electrodes. The subsequent discussion elaborates on effective strategies to achieve desirable properties, such as high conductivity, stretchability, skin adhesion, and biocompatibility. The emerging applications of permeable epidermal electrodes are also summarized. Finally, this review concludes with the current challenges and future directions of breathable epidermal electrodes.

Stretchable and Breathable Electroluminescent Displays Based on Ultrathin Nanocomposite Designs

“…Stretchable electronic devices are mostly built on elastomer substrates. Although elastomers are generally nonideal barriers for gas molecules, the commonly used sub-millimeter substrates are thick enough to block gas diffusion. , However, the human body continually evaporates water from the skin, even when at rest, which is a crucial physiological process for maintaining thermoregulation. , Covering the skin with impermeable devices may disrupt this process and lead to unpleasant sensations. , Furthermore, prolonged skin attachment with these devices produces adverse effects such as rashes and irritations within a few hours to days. , To address this issue, recent studies have made significant progress in developing highly breathable forms of skin-attached sensors. − On the other hand, textiles are currently the only permeable design for electroluminescent devices involving complex, multilayer structures. , Although the porous textiles naturally provide excellent permeability and improved wearing comfort, their woven fiber architecture leads to the discrete distribution of emissive elements . In spite of the capability to convey visual information, breathable textile displays often have drastically different visual appearances and operating mechanisms from regular displays built on rigid wafers.…”