Sensors are the core components of IoT terminal equipment. Wearable stress-strain sensors can be used to collect important human signals and human-computer interaction. In addition to the high-sensitivity features required for accurate sensing, practical applications have very high requirements for the sensor's wearing comfort, weight, reliability, and stability. Therefore, more sensitive, miniaturized and integrated are the current development trends of sensors. Integrating sensors into traditional fibers and using their advantages of direct weaving to clothing to accurately capture the local deformation of the human body is an important idea for miniaturization and integration of wearable sensor devices.
Graphene-polymer composite fiber has the advantages of light weight, low signal noise, low energy consumption, etc., and can be used for resistance type strain sensors. For sensing small local deformations of the human body such as heart beat, pulse and blinking, the strain is in the range of 0-10%, and the structure and resistance of the sensor device need to be changed greatly when the deformation occurs, that is, high sensitivity, so as to achieve accurate capture of Accurate identification of different action states. However, the sensitivity of graphene-based fiber sensors in the 0-10% strain range is generally low (GF ~ 0.1-50). How to improve the sensitivity of graphene-based fiber sensors in the small strain range is a difficult problem.
In order to solve the above problems, Ding Guqiao, a researcher at the Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, proposed a strategy to improve the sensitivity by reducing the contact area between graphene and polymers through structured design. Using the phase separation process of graphene / polyvinylidene fluoride / polyurethane DMF system in the aqueous phase, they prepared polymer nanosphere-modified graphene porous network fibers, which greatly enhanced the graphene sheet when the fiber deformed. The structure changes between layers, thereby achieving a significant increase in the sensitivity of graphene-based fibers. Its sensitivity factor value is 51 at 0-5% strain and 87 at 5-8% strain. Through braid integration, they further verified the accuracy of the fiber in collecting important signals of the human body and the feasibility of analyzing different action states. Sex. At the same time, this new graphene-based fiber sensor has a minimum deformation detection limit of 0.01%, and a good strain-resistance linear relationship can ensure the accuracy of signal post-processing. A cycle life of> 6000 times is conducive to the stability of practical applications. .
This fiber is woven into gauze and used as an eye mask to monitor the rotation of the eyeballs in real time. It can be used in the monitoring of eye diseases and sleep monitoring in the future. At the same time, the fiber is integrated into a wound stick and attached to the wrist to identify the wrist Pulse, and the pulse signal can clearly show different signals on the pulse; the fiber can also be knitted into gloves to sense the bending of different hands, indicating that it accurately controls the motion signal. It is precisely because of the existence of the small ball structure that the fiber is given higher sensitivity than ordinary fibers. The above results meet the requirements of wearable strain sensors and reflect the application potential of graphene-based strain sensors in smart medical and wearable devices. .