Advances in the preparation and sensing properties of ionogel fibers

<p indent="0mm">Flexible wearable electronics can monitor human physiological signals, movement information and environmental information in real time, providing intelligent medical and personal health management. With the rapid rise of implantable, wearable and portable electronic devices in the commercial market, as well as the booming development of artificial intelligence in the era of big data, wearable electronic devices show broader prospects in the future. In recent years, flexible stretchable wearable electronic devices have made remarkable progress, and have been widely used in the fields of health monitoring, human movement, human-computer interaction, and electronic skin. Ionogels are gel materials consisting of a solid supporting network as the matrix and ionic liquids (IL) dispersed inside. Due to the outstanding properties of IL, ionogels are endowed with a number of excellent properties, such as non-volatility, high thermal stability and high ionic conductivity. Through careful design of polymer networks, IL and the addition of functional fillers, ionogels have been characterised by new properties such as biodegradability, self-healing, luminescence and antimicrobial properties. The emergence and development of ionogel materials provide new opportunities for the development of high-performance flexible sensors. Compared to traditional films or block gels, one-dimensional ionogel fibers have the properties of flexibility, breathability, comfort and light weight, making them ideal for wearable electronics. Sensors constructed from ionogel fibers not only retain the structural advantages of fibers, such as the flexibility to adapt to the human body for stable human-device interfaces, implantation into deep tissues without causing traumatic tissue damage, and the ability to detect signals from multiple directions, but also have the properties of ionogels, which play an important role in flexible sensing and have become a research hotspot. In addition, ionogel fibers can be woven and integrated into fabrics, which are the basic unit of smart fabrics. They can realize the monitoring of human movement and vital signs signals, which have important applications and academic values in the fields of health monitoring, disease diagnosis and human-computer interaction, and open up a new way for smart fabric wearable electronic devices. The preparation and sensing properties of ionogel fibers in recent years are reviewed in this paper. Firstly, the properties of ionogels, such as mechanical properties, ionic conductivity and thermal stability are introduced and the parameters affecting their properties and improvement strategies are discussed. Then, the methods for discontinuous and continuous preparation of ionogel fibers are presented, including the tubular template method, the dip-coating method, the melt spinning method, the wet spinning method, the dynamic reactive spinning method and the thermo-spun reaction encapsulation method. Next, the sensing mechanism of ionogel fibers as flexible sensors is analyzed and discussed. The ionogel fibers convert the strain stimulus, temperature or pressure signals to electrical signals which can be classified as strain sensing, temperature sensing or pressure sensing according to their different sensing functions. The performances and applications of the sensor based on ionogel fibers are discussed. Finally, the challenges for the development of ionogel fibres are discussed in the light of recent research advances in the field, and suggestions for further research are made.