Soft Bioelectronic Stickers: Selection and Evaluation of Skin‐Interfacing Electrodes

Surface biopotentials collected from the human epidermis contain important information about human physiology, such as muscular, heart, and brain activities. However, commercially available wearable biomonitoring devices are generally composed of rigid hardware incompatible with the mechanical compl...

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Bibliographic Details
Published in:Advanced healthcare materials 2019-08, Vol.8 (15), p.e1900234-n/a
Main Authors: Lopes, Pedro Alhais, Vaz Gomes, Davide, Green Marques, Daniel, Faia, Pedro, Góis, Joana, Patrício, Tatiana F., Coelho, Jorge, Serra, Arménio, de Almeida, Aníbal T., Majidi, Carmel, Tavakoli, Mahmoud
Format: Article
Language:English
Subjects:
Alcohols
Bioelectricity
bioelectronic stickers
Biomonitoring
Brain
Circuits
Coated electrodes
Conductivity
Conductors
EKG
Electrocardiography
Electrodes
Electromyography
electronic skin
Epidermis
Human tissues
Hydrogels
Liquid metals
Multilayers
Nickel
PDMS
Polydimethylsiloxane
Polyvinyl alcohol
Silicone resins
Silver
Silver chloride
Skin
soft electrodes
Stainless steel
Stainless steels
stretchable electronics
Substrates
Wearable technology
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Summary:Surface biopotentials collected from the human epidermis contain important information about human physiology, such as muscular, heart, and brain activities. However, commercially available wearable biomonitoring devices are generally composed of rigid hardware incompatible with the mechanical compliance of soft human tissues. Thin‐film stretchable e‐skin circuits that can interface the human skin represent an excellent alternative for long‐term wearable biomonitoring. Here, a series of soft and stretchable electrodes are evaluated for their applicability in biopotential sensing. This includes conductive composites made of polydimethylsiloxane (PDMS) as a base substrate and conductive particles, i.e., carbon (cPDMS), silver (AgPDMS), anisotropic z‐axis conductors made with silver‐coated nickel particles (zPDMS), as well as a combination of a conductive tough hydrogel with PDMS, and finally ultrathin tattoo‐like adhesive poly(vinyl alcohol)‐coated films with stretchable biphasic Ag‐EGaIn electrodes. These electrodes are compared between themselves and against the gold‐standard Ag/AgCl and stainless steel electrodes, in order to assess relative performance in signal‐to‐noise ratio (SNR) during electrocardiography, and electrode‐skin impedance for a range of frequencies. Results show a direct relation between conformity of the electrode–skin interface and the SNR value. An all‐integrated biomonitoring patch with embedded processing and communication electronics, hydrogel electrodes, and a multilayer liquid metal circuit is presented for electromyography. A comprehensive comparative study of adhesive electrodes for soft wearable electronics and gold‐standard electrodes is presented. Impedance characterization and signal‐to‐noise ratio measurements rank hydrogel‐PDMS (polydimethylsiloxane) and “tattoo” electrodes higher than Ag/AgCl gel or stainless‐steel standards. Ease of integration of PDMS‐based electrodes is demonstrated on a wearable all‐integrated biomonitoring patch.
ISSN:2192-2640
2192-2659
DOI:10.1002/adhm.201900234