Highly stretchable, repeatable, and easy-to-prepare ionogel based on polyvinyl chloride for wearable strain sensors

Conventional hydrogels are prone to water loss and instability, while non-hydrogel materials can be designed with high stability and repeatability. Therefore, a flexible sensing material was developed to meet the requirements of high elasticity, good stability, and high repeatability using a simple physical blending method. The developed ionogel comprised polyvinyl chloride (PVC) gel as the elastomer matrix, ionic liquid (IL) 1-ethyl-3-methylimidazolium thiocyanate as the dielectric, and dibutyl adipate (DBA) as the plasticizer. The PVC organic-ionogel exhibited good physicochemical stability without any phase change in the range of − 30 to 127 °C, and it had a maximum tensile strain of 424 %. Its shape and dimensions remained unchanged in air for 60 days, and the sensing performance was maintained following exposure to air for over a year. Moreover, the PVC organic-ionogel with moderate DBA and IL contents (DBA 7, IL 3 %) showed the best performance, which exhibited the best linearity with a relative error of only 0.96 %, sensitivity of 1.90, modulus of 17.71 kPa, response time of 161 ms, and continuous and stable operation for 35,000 cycles. This excellent performance enabled the PVC organic-ionogel to detect a range of human movements, namely finger flexion, throat vibration, muscle contraction, daily movements, and special limb movements, such as Tai Chi, with high accuracy and sensitivity. This work provides a new approach for the design of flexible sensing materials with variable parameters, in addition to a new solution for the development of wearable devices, sports-related risk monitoring, and boxing action optimization.