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Interest in wearable and stretchable on‐skin motion sensors has grown rapidly in recent years. To expand their applicability, the sensing element must accurately detect external stimuli; however, weak adhesiveness of the sensor to a target object has been a major challenge in developing such practical and versatile devices. In this study, freestanding, stretchable, and self‐adhesive ionogel conductors are demonstrated which are composed of an associating polymer network and ionic liquid that enable conformal contact between the sensor and skin even during dynamic movement. The network of ionogel is formed by noncovalent association of two diblock copolymers, where phase‐separated micellar clusters are interconnected via hydrogen bonds between corona blocks. The resulting ionogels exhibit superior adhesive characteristics, including a very high lift‐off force of 93.3 N m−1, as well as excellent elasticity (strain at break ≈720%), toughness (≈2479 kJ m−3), thermal stability (≈150 °C), and high ionic conductivity (≈17.8 mS cm−1 at 150 °C). These adhesive ionogels are successfully applied to stretchable on‐skin strain sensors as sensing elements. The resulting devices accurately monitor the movement of body parts such as the wrist, finger, ankle, and neck while maintaining intimate contact with the skin, which was not previously possible with conventional non‐adhesive ionogels. [ABSTRACT FROM AUTHOR]

Stretchability and sensitivity are essential properties of wearable electronics for effective motion monitoring. In general, increasing the sensitivity of strain sensors based on ionic conductors trades off elasticity, which results in low sensitivity of the strain sensors at large mechanical deformations. To address this, ion‐permeable conducting polymer electrodes with low contact resistance are utilized in ionic gel‐based strain sensors. Using a rectangular‐shaped ionic gel and ion‐permeable electrodes significantly increase the gauge factor of the strain sensor, similar to the theoretical value at a given strain. To further increase the sensitivity of the strain sensor, the ionic gel is patterned with zigzagged tracks that gap apart as the gel stretches, and the gaps close as the gel contracts, leading to a large variation in the relative resistance upon stretching. By combining the zigzagged ionic gel and the ion‐permeable electrodes, highly sensitive stretchable sensors are realized with a record‐high gauge factor of 173, compared to existing ionic conductor‐based stretchable strain sensors. The zigzag‐patterned ionic sensor can successfully monitor various motions when attached to the human body. These results are expected to afford promising strategies for developing highly sensitive, stretchable sensing systems for E‐skin sensors and soft robotics. [ABSTRACT FROM AUTHOR]