Fabrication method of flexible strain sensors with CNTs and solvents

Flexible strain sensors have received a lot of attention for their various applications, such as electronic skins, healthcare devices, and human-machine interactions. In many studies of manufacturing flexible strain sensors using carbon nanotubes (CNTs), various solvents are used to disperse CNTs. However, most studies lack explanation of the rationale for using specific solvent, which is mainly used to disperse CNTs and make CNT solution. There are studies dealing with the degree of dispersion in specific solvent of CNTs, but these studies lack information on solvents in the sensor manufacturing process. Therefore, researchers have difficulty in determining which solvent to use for CNT dispersion in their process because solvent selection varies depending on the sensor manufacturing method. Thus, the dispersion stability of CNT solutions with several solvents and the characteristics of CNT sheets made from each CNT solution were quantitatively compared. Then, the solvent suitable for an acrylic mold as well as having high dispersion stability was selected. Moreover, the flexible CNT strain sensor is developed by transferring CNTs to a flexible substrate. This sensor can be stretched up to 150% (linearity R=0.998), and the gauge factor was 26.7. It is expected to be used in various research of wearable sensors or human motion monitoring using CNT dispersion.