Flexible Multidirectional Strain Sensor Based On Aligned Carbon Nanotubes And Its Application

Flexible strain sensors have extensive application prospects in the realms of personal health monitoring and sports training monitoring because of their ability to accurately capture the strain information of the human epidermis.The most widely studied uniaxial strain sensor can easily record the simple bending motion of human joints,but it is not powerful enough in the face of complex and multi-dimensional actual motion scenarios.Therefore,in order to expand the dimension of mechanical information that can be perceived by flexible strain sensors,multi-axial strain sensors need to be constructed.Today,multi-dimensional mechanical sensing can be achieved mainly through the following three strategies:(1)stacking different types of mechanical sensing devices in a sensing system;(2)constructing a mechanical sensing matrix;(3)using anisotropic materials to deconstruct multidimensional mechanical information.Among them,the multi-dimensional mechanical sensor prepared with anisotropic materials has a simple preparation method and low requirements for supporting circuits,and is considered to be an effective strategy for obtaining multiaxial mechanical information.In this academic dissertation,the core sensing material of the flexible biaxial strain sensor was prepared by compounding highly aligned carbon nanotubes with an anisotropic conductive network and polyacrylamide hydrogel.The composites were characterized by means of X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM),and high-resolution transmission electron microscopy(HRTEM).After that,a multi-axial flexible strain sensor was fabricated by orthogonally stacking two rectangular aligned carbon nanotubes films,further strengthening the sensor’s ability to acquire complex strain information.Finally,the performance of these two types of non-uniaxial sensors and application potential in real life scenarios is investigated by constructing the relationship between strain and electrical signal.The followings are conclusions:1.The composite of carbon nanotubes and polyacrylamide hydrogel not only improves the electrical conductivity and strain sensing performance of the original hydrogel,but also endows carbon nanotubes with greater elastic deformation ability.Carbon nanotubes,as strong cross-linking sites,are fully integrated into the hydrogel polymer network.When the amount of strain exceeds the elastic deformation range of the original carbon nanotubes,the hydrogel deeply cross-linked with the carbon nanotubes partially restores the original structure of the carbon nanotubes by its own resilience.2.The biaxial strain sensor prepared in this paper is more sensitive to the strain change along the carbon nanotube tube axis.Because the highly aligned carbon nanotubes are more closely arranged along the axis of carbon nanotubes,the conductive paths in this direction are damaged more seriously during the stretching process,resulting in greater changes in electrical signals.Utilizing this feature,it is possible to clearly distinguish the strain changes in the two directions along the carbon nanotube axis and perpendicular to the carbon nanotube axis.3.The multidirectional strain sensor fabricated by stacking two biaxial strain sensors orthogonally in space can identify strain information from more angles.By comprehensively analyzing the strain information from two directions at the same time,the multidirectional strain sensor has incomparable advantages over the uniaxial strain sensor for the complex motion of the same part of the human body with multiple degrees of freedom.