To date, ionogel sensors have aroused the extensive interest as an alternative to hydrogel sensors, as they are promising materials to solve the problems of easy drying and easy freezing. However, the weak mechanical properties of ionogels have seriously hindered their large-scale application. Herein, a robust physically linked double-network ionogel (DN ionogel) was fabricated via interpenetrating a poly­(hydroxyethyl acrylate) network into an agarose network in 1-ethyl-3-methylimidazolium chloride. The DN ionogel possessed good mechanical properties, high transparency, extreme temperature tolerance, and excellent self-adhesion. The superior electromechanical properties render the DN ionogel as a perfect candidate to be utilized as a strain sensor to monitor various human activities. In addition, the DN ionogel exhibited reasonably high sensitivity to temperature. Therefore, it is believed that this high performance strain–temperature bimodal sensor offers a promising prospect in flexible intelligent electronics.

Different from conductive hydrogels, ion gels, another kind of ionic conductor, possess excellent nonvolatility and anti-freezing capability, which have attracted increasing research interest in electronic field. Nevertheless, the poor mechanical property of ion gels severely hinders their application in flexible strain sensors. Herein, an ionic conductor composed of poly­(acrylic acid) (PAA) within the ionic liquid 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM]­TfO) was synthesized by facile one-pot photopolymerization. The resulting ion gel exhibited extreme stretchability (1200%), high transparency (over 90%), good environmental stability, and outstanding self-adhesion. The remarkable electromechanical characteristics, including fast response speed, high sensitivity, low electrical hysteresis, and autonomous repeatability, endow the PAA ion gel with superior strain-sensing capability to monitor various human motions. Additionally, the PAA ion gel displayed rapid response speed and high sensitivity to temperature change. Therefore, this multifunctional ion gel-based flexible bimodal sensor provides broad prospects for wearable electronics.

Liquid conductor-based flexible sensors with high mechanical deformability and reliable electrical reversibility have aroused great interest in electronic skin, soft robotics, environmental monitoring, and other fields. Herein, we develop a novel strategy to fabricate liquid conductor-based flexible sensors by combining ionic liquid-based magnetofluids (IL-MFs), magnetic printing, and photopolymerization techniques. The as-prepared sensors exhibit excellent electromechanical properties, such as a wide detection range, low hysteresis, fast response time, good durability, etc. Moreover, the gauge factors (GFs) of the sensor could be easily adjusted by changing the modulators with different line widths or patterns, and the strain sensors can also be designed for anisotropic monitoring. Apart from serving as strain sensors, the magnetofluid-based flexible sensors can be used to detect external pressure, human activities, and changes in temperature, illumination, and magnetic field as well. This work provides a facile strategy to fabricate liquid conductor-based multifunctional sensors. Such a magnetofluid-based sensor has a great promising future.

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