A Super‐Stretchable and Highly Sensitive Carbon Nanotube Capacitive Strain Sensor for Wearable Applications and Soft Robotics

Abstract

The study of flexible and stretchable strain sensors is growing rapidly owing to the demands for human motion detection, human–machine interaction, and soft robotics. However, super‐stretchable and highly sensitive strain sensors with high linearity and low hysteresis are especially lacking, which therefore limits the use of soft strain sensors in varied practical applications. The stretchability and sensitivity of the capacitive strain sensor are constrained by the material characteristics and structure of parallel plate capacitor (theoretical gauge factor [GF] is 1). To address these limitations, a super‐stretchable and highly sensitive capacitive strain sensor composed of two strips of wrinkled carbon nanotubes‐based electrodes separated by a tape dielectric, is presented. By integrating nanomaterials and wrinkled film structure, this device achieves a GF of 2.07 at 300% strain with excellent linearity and negligible hysteresis. This is the first type of capacitive strain sensors that can achieve super‐stretchability and sensitivity simultaneously. Additionally, the sensor has a fast signal response time of ≈80 ms, and good mechanical durability during 1000 stretching and releasing cycles. The authors demonstrate the use of this sensor as a versatile wearable device for human motion tracking, and as a smart real‐time monitoring device for soft pneumatic robots.

Flexible and Stretchable Carbon-Based Sensors and Actuators for Soft Robots

“…The film electrodes were prepared by spray-coating CNTs onto stretchable films. After assembling films with electrodes onto the prestretched tape and releasing the tape, the electrodes will be wrinkled, therefore equipping the device with higher stretchability [ 140 ].…”

Versatile nano–micro collagen fiber-based wearable electronics for health monitoring and thermal management

“…With the development of wearable electronics, exible strain sensors have drawn vast attention due to their capabilities of capturing postures and monitoring various human activities by transducing tensile and compressive strains into electrical signals, [1][2][3] which make them applicable to personalized health monitoring, 4,5 human-machine interfaces, [6][7][8] so robots, [9][10][11] etc. Over the decades, exible strain sensors with various transduction mechanisms have been developed successfully, including piezoelectricity, capacitance, piezoresistivity, etc.…”

Cross-Talk Signal Free Recyclable Thermoplastic Polyurethane/Graphene-Based Strain and Pressure Sensor for Monitoring Human Motions

“…The basic human nature to improve the standard of living has always motivated us to develop new high-performance materials and devices. Expectedly, highly flexible, stretchable, and sensitive wearable sensors are gaining interest from both academic and industrial research because of their applications in human and structural health monitoring, − soft robotics, , sports performance monitoring, , and human–machine interactions involving the currently developing virtual reality, augmented reality, and gaming applications. , Further, in light of recent developments in customized healthcare systems, researchers are concentrating their efforts on the creation of cutting-edge wearable electronic gadgets that are both flexible and capable of monitoring human motions. The sensors that are being utilized are based on metals and semiconductors.…”