Portable, extensible and flexible voltage sensors can withstand high voltages. In a recent article in the journal npj Flexible Electronics, researchers developed voltage sensors based on graphene / ecoflex composites using multiscale / hierarchical wrinkle modulations on the flexible-ecoflex substrate, for the detection of a wide range of physiological signals such as pulse control, body. movements and speech recognition.
Study: graphene / Ecoflex sensors enhanced by multiscale and hierarchical wrinkles integrated with man-machine interfaces and cloud platform. Image credit: amgun / Shutterstock.com
The graphene sensors designed in the present study were highly sensitive with a gauge factor (GF) of 1078.1 and showed 650% stretchability with a response time of approximately 140 milliseconds and improved cycle durability. . These graphene-based sensors were integrated into a cloud platform to monitor human respiration, showing the potential of graphene sensors in healthcare applications.
The built-in graphene sensors also allowed the accurate detection of complex sign languages or gestures. In addition, the integration of graphene sensors into the glove of the man-machine interface could remotely control a manipulator to deactivate a pump from a distance, which is applicable in military fields and manufacturing industries.
Properties of voltage sensors
Mechanical deformations caused by the application of high stress on flexible / stretchable / flexible / curved substrates become electrical signals, promoting their applications in monitoring systems in the healthcare field, smooth robotics and human-machine interactions. Tension sensors that are flexible / stretchable / portable can withstand significant deformations and stresses up to 500% compared to their rigid counterparts.
Extensible voltage sensors are commercially available as resistive, capacitive, triboelectric and piezoelectric sensor types. Resistive voltage sensors are used for laptop sensing applications due to their simple structures, reliable reading circuit and cost-effective microfabrication processes. In addition, they offer high sensitivity, good elasticity and flexibility.
Graphene has extraordinary properties such as high carrier mobility, superior electrical and thermal conductivities, large surface area, high Young modulus, high optical transmittance and excellent mechanical flexibility.
Graphene is a promising two-dimensional (2D) material for various applications, especially in the development of portable sensors and implantable devices that could be applied in health surveillance.
To achieve practical applications of sensors, it is vital that these sensors have great extensibility and high sensitivity. Because stretchability and sensitivity are contradictory parameters, various methods of surface and interface engineering are proposed to achieve high sensitivity and stretchability.
The application of wrinkle structure is one of the reliable strategies to achieve the requirements of sensitivity and stretchability. Although several researchers have proposed different stress sensors based on the wrinkled structure, their sensitivity and extensibility were limited.
Improved graphene / Ecoflex sensors against wrinkles
In the present study, voltage sensors based on flexible graphene / ecoflex composite were fabricated using an interface engineering strategy, in which a wrinkle mechanism was applied to the ecoflex substrate. A cost-effective two-step method was used for surface treatment of the ecoflex substrate to form micro-nanoscale wrinkle patterns.
Characterization of the designed graphene / ecoflex compounds using a scanning electron microscope (SEM) revealed that after ecoflex surface treatment, it showed micron-sized wrinkles in large numbers on its surface. These were formed by rapid volatilization of ethanol, resulting in uneven surface morphology, which increased the ecoflex surface. This surface treatment improves the specific surface areas of ecoflex and improves the interfacial bond between graphene and ecoflex, thus improving the stress sensitivity of graphene stress sensors.
The graphene voltage sensors manufactured showed a high sensitivity with a GF of 1078.1, a significantly large extensibility with a voltage retention capacity of up to 650%, good cycle durability and such a short response time. like 140 milliseconds.
Designed graphene-based voltage sensors could capture and detect a wide range of physiological signals from speech sound, pulse vibration, and vigorous body movements. These graphene sensors could be applied to flexibly monitor human respiration for multiple users and a real-time cloud platform.
A man-machine interface integrated with the designed graphene sensors could demonstrate the detection of complex sign languages and gestures and can perform remote pump deactivation. The sensor-integrated glove could remotely control the external manipulator that performed the tests for sensor detection.
Conclusion
In summary, the multiscale and hierarchical wrinkle modulation methodology on a flexible ecoflex substrate was successful in its integration into stress sensors. The optimized design could achieve sensors with high sensitivity. The manufactured graphene sensors showed a GF of 1078.1, an extensibility of up to 650% and a short response time of approximately 140 milliseconds.
The graphene sensors obtained could detect various physiological signals. In addition, these sensors were applied for remote monitoring of sanitary devices. The integration of graphene-based sensors into a real-time cloud platform and a human-machine interface glove indicated their potential application to the healthcare industry and remote pump deactivation, respectively.
The present work highlighted the application of graphene sensors in long-range, real-time medical diagnoses. These graphene sensors also helped perform dangerous tasks from a distance, which is useful in industrial and military fields.
Reference
Zhou, J., Long, X., Huang, J., Jiang, C., Zhuo, F., Guo, C., Li, H. et al. (2022). Graphene / Ecoflex sensors enhanced for integrated multiscale and hierarchical wrinkles with man-machine interfaces and cloud platform. npj Flexible electronics. https://www.nature.com/articles/s41528-022-00189-1
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