An ambient-stable and stretchable ionic skin with multimodal sensation

Ying, Binbin; Wu, Qun; Li, Jianyu

doi:10.1039/c9mh00715f

Cited by 115 publications

(114 citation statements)

References 65 publications

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“…To meet the stringent requirements of flexible electronics and soft machines, ionic conductors are naturally desired to possess excellent mechanical properties—including ruggedness and self‐healing capability—and attributes such as optical transparency and high conductivity. Hydrogels containing mobile ions, which are stretchable, transparent, and conductive, are considered as promising candidates for ionic conductors, and have enabled many hydrogel‐based applications such as ionic skins, [ 11–13 ] soft actuators, [ 14 ] and energy harvesting devices. [ 15,16 ] These devices, however, often suffer from limitations inherent to hydrogels, which are unstable due to rapid evaporation of water in ambient conditions and do not adhere well to other materials.…”

Section: Figurementioning

confidence: 99%

A Mechanically Robust and Versatile Liquid‐Free Ionic Conductive Elastomer

et al. 2021

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Soft ionic conductors, such as hydrogels and ionogels, have enabled stretchable and transparent ionotronics, but they suffer from key limitations inherent to the liquid components, which may leak and evaporate. Here, novel liquid‐free ionic conductive elastomers (ICE) that are copolymer networks hosting lithium cations and associated anions via lithium bonds and hydrogen bonds are demonstrated, such that they are intrinsically immune from leakage and evaporation. The ICEs show extraordinary mechanical versatility including excellent stretchability, high strength and toughness, self‐healing, quick self‐recovery, and 3D‐printability. More intriguingly, the ICEs can defeat the conflict of strength versus toughness—a compromise well recognized in mechanics and material science—and simultaneously overcome the conflict between ionic conductivity and mechanical properties, which is common for ionogels. Several liquid‐free ionotronics based on the ICE are further developed, including resistive force sensors, multifunctional ionic skins, and triboelectric nanogenerators (TENGs), which are not subject to limitations of previous gel‐based devices, such as leakage, evaporation, and weak hydrogel–elastomer interfaces. Also, the 3D printability of the ICEs is demonstrated by printing a series of structures with fine features. The findings offer promise for a variety of ionotronics requiring environmental stability and durability.

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Section: Figurementioning

confidence: 99%

A Mechanically Robust and Versatile Liquid‐Free Ionic Conductive Elastomer

et al. 2021

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“…5 Department of Materials Science and Engineering, University of Toronto, Toronto, ON, Canada. 6 Department of Chemistry, University of Toronto, Toronto, ON, Canada. 7 Department of Nanotechnology Engineering, University of Waterloo, Waterloo, ON, Canada.…”

Section: Abbreviationsmentioning

confidence: 99%

Evaluation of dry textile electrodes for long-term electrocardiographic monitoring

et al. 2021

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Background Continuous long-term electrocardiography monitoring has been increasingly recognized for early diagnosis and management of different types of cardiovascular diseases. To find an alternative to Ag/AgCl gel electrodes that are improper for this application scenario, many efforts have been undertaken to develop novel flexible dry textile electrodes integrated into the everyday garments. With significant progresses made to address the potential issues (e.g., low signal-to-noise ratio, high skin–electrode impedance, motion artifact, and low durability), the lack of standard evaluation procedure hinders the further development of dry electrodes (mainly the design and optimization). Results A standard testing procedure and framework for skin–electrode impedance measurement is demonstrated for the development of novel dry textile electrodes. Different representative electrode materials have been screen-printed on textile substrates. To verify the performance of dry textile electrodes, impedance measurements are conducted on an agar skin model using a universal setup with consistent frequency and pressure. In addition, they are demonstrated for ECG signals acquisition, in comparison to those obtained using conventional gel electrodes. Conclusions Dry textile electrodes demonstrated similar impedance when in raised or flat structures. The tested pressure variations had an insignificant impact on electrode impedance. Looking at the effect of impedance on ECG signals, a noticeable effect on ECG signal performance metrics was not observed. Therefore, it is suggested that impedance alone is possibly not the primary indicator of signal quality. As well, the developed methods can also serve as useful guidelines for future textile dry-electrode design and testing for practical ECG monitoring applications.

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“…This reflects that the i-TPU film is highly reliable against repeated strains which would be generated by human motion. [44][45][46] Eventually, it can be expected that the i-TPU based IGS can be a promising skin-like material, and possesses considerable potential for the realization of skinattachable electronics.…”

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confidence: 99%

Scalable Superior Chemical Sensing Performance of Stretchable Ionotronic Skin via a π‐Hole Receptor Effect

et al. 2021

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Soft, skin-attachable sensing devices have enabled the perception of infinitesimal changes in the surroundings (i.e., pressure and temperature) for intelligent robots, medical diagnostics, and real-time health monitoring. [1,2] In artificial sensing platforms, additional functionalities for chemical and biological sensing are designed to incorporate and facilitate a high quality of life. [3,4] Because exposure to toxic chemicals leads to millions of deaths worldwide annually, the use of skin-attachable platforms for sensing toxic gases has attracted considerable attention. [5] For example, toxic nitrogen dioxide (NO 2) gas molecules from automotive emissions are associated with respiratory mortality and morbidity, thus it must be monitored along with other toxic chemicals. [6,7] To realize the practical sensing of toxic gases via skin-attachable devices, the sensor should be designed with longterm stability (chemical, thermal, and mechanical robustness that enable reliable collection of sensing signals on the human Skin-attachable gas sensors provide a next-generation wearable platform for real-time protection of human health by monitoring environmental and physiological chemicals. However, the creation of skin-like wearable gas sensors, possessing high sensitivity, selectivity, stability, and scalability (4S) simultaneously, has been a big challenge. Here, an ionotronic gas-sensing sticker (IGS) is demonstrated, implemented with free-standing polymer electrolyte (ionic thermoplastic polyurethane, i-TPU) as a sensing channel and inkjet-printed stretchable carbon nanotube electrodes, which enables the IGS to exhibit high sensitivity, selectivity, stability (against mechanical stress, humidity, and temperature), and scalable fabrication, simultaneously. The IGS demonstrates reliable sensing capability against nitrogen dioxide molecules under not only harsh mechanical stress (cyclic bending with the radius of curvature of 1 mm and cyclic straining at 50%), but also environmental conditions (thermal aging from −45 to 125 °C for 1000 cycles and humidity aging for 24 h at 85% relative humidity). Further, through systematic experiments and theoretical calculations, a π-hole receptor mechanism is proposed, which can effectively elucidate the origin of the high sensitivity (up to parts per billion level) and selectivity of the ionotronic sensing system. Consequently, this work provides a guideline for the design of ionotronic materials for the achievement of highperformance and skin-attachable gas-sensor platforms.

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An ambient-stable and stretchable ionic skin with multimodal sensation

Abstract: A diode-like artificial ionic skin for strain and humidity sensing with controlled ion mobility, high toughness, stretchability, ambient stability and transparency.

Cited by 115 publications

References 65 publications

A Mechanically Robust and Versatile Liquid‐Free Ionic Conductive Elastomer

A Mechanically Robust and Versatile Liquid‐Free Ionic Conductive Elastomer

Evaluation of dry textile electrodes for long-term electrocardiographic monitoring

Scalable Superior Chemical Sensing Performance of Stretchable Ionotronic Skin via a π‐Hole Receptor Effect

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