All-Organic, Solution-Processed, Extremely Conformal, Mechanically Biocompatible, and Breathable Epidermal Electrodes

Abstract

Conformal integration of an epidermal device with the skin, as well as sweat and air permeability, are crucial to reduce stress on biological tissues. Nanofiber-based porous mesh structures (breathable devices) are commonly utilized to prevent skin problems. Noble metals are normally deposited on nanomesh substrates to form breathable electrodes. However, these are expensive and require high-vacuum processes involving time-consuming multistep procedures. Organic materials are suitable alternatives that can be simply processed in solution. We report a simple, cost-effective, mechanically biocompatible, and breathable organic epidermal electrode for biometric devices. Poly­(3,4-ethylenedioxythiophene):poly­(styrene sulfonate) (PEDOT:PSS) is sprayed on a nanofiber-mesh structure, treated using only heat and water to enhance its biocompatibility and conductivity, and used as the electrode. The treatment is accomplished using an autoclave, simultaneously reducing the electrical resistance and sterilizing the electrode for practical use. This research can lead to affordable and biocompatible epidermal electrodes with improved suitability for various biomedical applications.

Mass and Charge Transport Kinetics in an Organic Mixed Ionic–Electronic Conductor

“…20 The material is readily processable into different geometries for various applications, such as thin films, 13,21 fibers, 22 and free-standing electrodes. 23,24 Acid-treated PEDOT/PSS is a promising model system for OMIEC studies, not only because of its high OECT performance but also for the compositional/ structural simplicity. There is no requirement for extra additives, such as ethylene glycol, dimethyl sulfoxide, ionic liquids, surfactants, and cross-linkers.…”

“…28,29 For acid-treated PEDOT/PSS, the electronic properties have been characterized by thin films and fibers by measuring stain-dependent electronic conductivity and μC*, 22,30 showing both improved electronic mobility and volumetric capacitance after acid treatment. 22 Electron microscopy and atomic force microscopy have revealed well-crystallized nanofibers, 18,21,23,24 and ex situ Xray diffraction (XRD) provides molecular spacings and orientation of these crystallites. 19,22 In addition, both X-ray photoelectron spectroscopy (XPS) and optical absorption spectroscopy confirm the removal of PSS with acid treatment.…”

Highly Conformal Polymers for Ambulatory Electrophysiological Sensing

“…As is well-known, natural biopolymers are chain-like polymeric materials with different repetitive units, including amino acids, glucose, and their derivatives. [79,80] They are famed for natural abundance, low cost, excellent mechanical performance, superior biocompatibility, as well as favorable renewability. Additionally, their diverse chemical compositions and reactive groups realize easy processability and desirable tunability for structures and functionalities.…”

Permeable Conductors for Wearable and On‐Skin Electronics

“…f–h) Reproduced with permission. [ 74 ] Copyright 2021, American Chemical Society. i) Schematic illustration showing the fabrication process of Ag NPs‐coated SBS fiber mat through precursor reduction.…”

“…The e‐tattoos could be conformably attached to the irregular dermal surface and preserve their functions when mechanical stresses deform the skin, demonstrating their application possibilities for on‐skin diagnostics and therapeutics [67d] . Jeong et al [ 74 ] fabricated the breathable, flexible, and biocompatible PEDOT:PSS‐based epidermal electrodes for ECG monitoring by spraying the PEDOT:PSS aqueous solution onto the PU electrospun mats (Figure 6g–j). The as‐made electrode could exhibit stretchability with a maximum elongation of 30%, high conductivity at 125.4 S m −1 , and moisture permeability with a WVTR of about 12 g m −2 h −1 (288 g m −2 day −1 ) (Figure 6k).…”