Construction And Research Of Flexible Capacitive Sensor Based On Nanofibers

The development of highly sensitive,stretchable,and wearable electronic skin is of great value for application in human health monitoring,robot skin,and intelligent electronic devices.Due to its large specific surface area,high porosity and small size,electrospinning nanofiber has an excellent application prospect in the field of flexible sensors.In order to construct the capacitance sensor with high sensitivity by using low-cost electrospinning technology,in this paper,the film-based and textile-based capacitance sensors have been studied in-depth,respectively.（1）Flexible and conductive CNT/PDMS composite films are prepared by combining CNT conductive particles with PDMS polymer matrix.The polyimide nanofiber aerogel with excellent elastic is prepared by a simple electrospinning method.A flexible wearable pressure-sensitive film-based capacitive sensor is constructed with the CNT/PDMS films serve as the upper and lower electrodes and nanofiber aerogel as the dielectric layer.The pressure sensing performance of the capacitive sensor is tested.The results show that the capacitive sensor has good repeatability and stability to pressure sensing,the capacitive response varies with pressures and a wide pressure monitoring range（⁴000Pa）.In addition,the sensor has been proved to have excellent performance in the monitoring of micro stress.Upon the release of loading force,the capacitance return to the original state quickly.（2）A core-spun yarn is obtained by coating a GO-doped PU nanofiber on the surface of the Ni-coated cotton yarn via the technology of electrospinning nanofiber core-spun yarn.And further,the elastic composite yarn is formed by the core-spun yarn helically wound around the surface of the elastic thread.Then,the elastic composite yarn can be woven into a large-area fabric according to the method of plain weave which can simultaneously monitor multiple mechanical stresses and has a good sensing performance to noncontact finger proximity.A capactive type sensor unit forms at the cross contact of the fabric,and its sensing properties such as pressure,lateral strain,flexion and finger proximity are tested and analyzed comprehensively.The results show that,the three dimensional elastic porous nanofiber structure of the dielectric layer,the fiber aggregate structure of the conductive electrode,and the helical structure of the elastic composite yarn play key roles in allowing the sensor unit of the electronic fabric to improve sensitivity,realize multiple-force sensitivities and realize stretchable and woven wearability.The sensor unit that can induce a large contact-area accumulation of the nanofiber dielectric layers under low external force exhibits excellent sensitivity(1.59 N^-1,<0.3 N),a wide sensing range（0-5 N）,a low detection limit（0.001 N）,a short response time,good cycling stability and repeatability,as well as high strain sensitivity over a wide range（0-100%）.In addition,electronic fabric have also been shown to be suitable for voice recognition,noncontact airflow monitoring,finger and wrist muscle movements,and noncontact proximity of fingers.This flexible,elastically woven textile-based sensor demonstrates potential applications in wearable electronic devices and humanoid robots.