Block Copolymer-Based Supramolecular Ionogels for Accurate On-Skin Motion Monitoring

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 approximate to 720%), toughness (approximate to 2479 kJ m(-3)), thermal stability (approximate to 150 degrees C), and high ionic conductivity (approximate to 17.8 mS cm(-1) at 150 degrees 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.

Automated summary

This study demonstrated the development of freestanding, stretchable, and self-adhesive ionogel conductors for wearable and stretchable on-skin motion sensors. These ionogels exhibit superior adhesive characteristics and high ionic conductivity, enabling intimate contact between the sensor and skin during dynamic movement, providing accurate monitoring of body parts.