Highly Thermal-Wet Comfortable and Conformal Silk-Based Electrodes for On-Skin Sensors with Sweat Tolerance

Abstract

Noninvasive and seamless interfacing between the sensors and human skin is highly desired for wearable healthcare. Thin-film-based soft and stretchable sensors can to some extent form conformal contact with skin even under dynamic movements for high-fidelity signals acquisition. However, sweat accumulation underneath these sensors for long-term monitoring would compromise the thermal-wet comfort, electrode adherence to the skin, and signal fidelity. Here, we report the fabrication of a highly thermal-wet comfortable and conformal silk-based electrode, which can be used for on-skin electrophysiological measurement under sweaty conditions. It is realized through incorporating conducting polymers poly­(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS) into glycerol-plasticized silk fiber mats. Glycerol plays the role of tuning the mechanical properties of silk fiber mats and enhancing the conductivity of PEDOT:PSS. Our silk-based electrodes show high stretchability (>250%), low thermal insulation (∼0.13 °C·m2·W–1), low evaporative resistance (∼23 Pa·m2·W–1, 10 times lower than ∼1.3 mm thick commercial gel electrodes), and high water-vapor transmission rate (∼117 g·m–2·h–1 under sweaty conditions, 2 times higher than skin water loss). These features enable a better electrocardiography signal quality than that of commercial gel electrodes without disturbing the heat dissipation during sweat evaporation and provide possibilities for textile integration to monitor the muscle activities under large deformation. Our glycerol-plasticized silk-based electrodes possessing superior physiological comfortability may further engage progress in on-skin electronics with sweat tolerance.

Bioinspired Perspiration‐Wicking Electronic Skins for Comfortable and Reliable Multimodal Health Monitoring

“…The WER was 0.85 g h –1 (Figure 3f), not only higher than cotton (≈7.1 times), Nylon (≈5.7 times), and CM (≈2.1 times) but also higher than TPU/CM (≈1.9 times) and the state‐of‐the‐art sweat‐wicking fabrics or electrodes (Table S1, Supporting Information). [ 15,18b,21,24 ] Compared to pure CM, the unidirectional water transport of Au/TPU/CM promotes the water transport to CM surface where evaporation is easier than that in the bulk, thus doubling the evaporation rate. Compared to TPU/CM, the improved transport directionality also leads to a higher WER of Au/TPU/CM.…”

“…[ 14 ] Chen et al incorporate conducting polymers into glycerol plasticized silk fiber mats. [ 15 ] Despite the improved breathability, the perspiration removal between skin and sensors still relies on natural evaporation rather than active absorption. As a result, the accumulated sweat cannot be removed immediately and effectively in many cases such as hot and/or humid environments, outdoor activities, intense exercise, heavy load workers, and patients with hyperhidrosis.…”

Antimicrobial second skin using copper nanomesh

“…Thin and highly conformal nanomesh coated with copper, one of the most thermally conductive materials, conveys heat, which can lead to a proper thermal sensation. Due to the advantageous mesh structure ( 62 ), the transport of water, air, and heat was enabled without a huge change from the bare skin. Additionally, we have previously demonstrated that the metal-coated nanomesh preserves the pressure sensing of the skin without any disturbance or distortion ( 63 ).…”

Delamination-Resistant Imperceptible Bioelectrode for Robust Electrophysiological Signals Monitoring

“…We rationalize that DrIE requires the PEDOT:PSS-based film with both consecutive conductive domain and dispersed flexible insulating domain. Although untreated PEDOT:PSS can effectively transport electrons, its conductivity is relatively low and stretchability is very limited (morphological scheme illustrated in Figure a, left). ,, Blending glycerol can reduce electrostatic interaction between PEDOT and PSS, leading to phase separation, which allows PEDOT partially aggregation to form a conductive network, while leaving PSS as a dispersed soft matrix . Moreover, the polar groups of dopants like glycerol induce a driving force to endow aggregated PEDOT domains with a conformational change, where the benzoid structure transforms to the quinoid structure (Figure a, middle), resulting in a further increase of the intramolecular conductance for PEDOT domains .…”

“…14,15,21 Blending glycerol can reduce electrostatic interaction between PEDOT and PSS, leading to phase separation, which allows PEDOT partially aggregation to form a conductive network, while leaving PSS as a dispersed soft matrix. 22 Moreover, the polar groups of dopants like glycerol induce a driving force to endow aggregated PEDOT domains with a conformational change, where the benzoid structure transforms to the quinoid structure (Figure 1a, middle), resulting in a further increase of the intramolecular conductance for PEDOT domains. 23 However, the glyceroldoped PEDOT:PSS cannot maintain high conductivity under large strain, because of the insufficient bridging between PEDOT and PSS domains.…”