Ionic liquid-enhanced Nafion-based ionic polymer sensors: Impact of immersion temperature and imidazolium types

Flexible sensors have broad application prospects in fields of medical electronics, environmental monitoring and wearable devices. Among them, ionic polymer sensors (IPS), with the sensing mechanism resembling biological processes, have drawn significant attention. Traditional Nafion-based IPS using water and alkali metal cations as electrolyte suffer from issues like performance degradation and signal instability water evaporation. Ionic liquids (ILs), as solvent-free electrolytes, hold promise in solving these problems. However, the impact of ILs on Nafion-based IPS performance remains unclear. In this paper, we investigated the influence of various parameters during the IL immersion process on IPS performance. By adjusting immersion temperature and time, different samples were prepared, whose mass change, stiffness, surface resistance and the electrochemical performance are studied. Furthermore, the influence of imidazolium type on sensing performance of IPS is also explored. Then an IL-based IPS sensor with optimal performance is obtained, the sensitivity of which was increased by 150 % and the sensing stability was greatly improved compared with the traditional water-based IPS. The application potential of the IL-based IPS in human motion monitoring was explored, including swallowing, speaking, mouse operation, pulse, knee joint movement and gait. The results of this work prove the effectiveness of obtaining high-performance Nafion-based IPS with IL as electrolyte through direct heating and immersion, and are expected to contribute to the rapid preparation of high-stability IPS.