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The advent of the Internet of Things (IoT) has sparked a great deal of interest in multi-functional wearable electronic devices. These devices are able to monitor a variety of physical stimuli in real time, including pressure, strain, temperature and humidity. Their potential applications in human health monitoring, e-skin, smart hyperthermia, and human-computer interaction have attracted considerable attention. Various sensing technologies have been used to successfully construct flexible strain sensors based on capacitive, piezoresistive, piezoelectric, triboelectric, etc.
The main point of this paper
The importance of piezoresistive flexible strain sensor:
These sensors are capable of monitoring physiological data generated by human movement and activity and have important implications for personal safety and health.
Wearable devices can be affected by electromagnetic interference (EMI), so there is a need to develop versatile wearable materials that can shield electromagnetic radiation.
Research progress of multifunctional devices:
The researchers are working to integrate conductive materials with flexible substrates to create multifunctional, flexible sensors.
Examples are given of research work such as that of Wang et al., and Zong et al., who have developed flexible multifunctional electronics with EMI shielding, Joule heating, and strain sensing, respectively, and wearable devices with strong EMI shielding and passive radiation heating capabilities.
Application of carbon aerogel:
Carbon aerogel has been widely used in various applications because of its controllable three-dimensional hierarchical structure, low density, remarkable adsorption capacity and high porosity.
Carbon aerogel is also one of the key components for creating high-performance wearable sensors.
Polyimide (PI) applications:
PI is widely used in many industries due to its excellent heat resistance, mechanical properties and chemical resistance.
PI can be converted into carbon material by carbonization process, which has the advantages of high carbon production rate, simple carbonization and graphitization process, and good electrical and thermal conductivity.
Multifunctional piezoresistive sensors based on carbon Electrospun Nanofbers Aerogel (PI-CNA) :
A multifunctional piezoresistive sensor based on carbon Electrospun Nanofbers aerogel was prepared by using polyimide as raw material.
The effects of carbonization temperature on the microstructure, density and conductivity of PI Electrospun Nanofbers aerogel were studied.
The application performance of PI-CNA materials in the comprehensive monitoring of human activity was evaluated, including the detection of intense movement and subtle physical activity.
The electromagnetic interference shielding performance and joule heating performance of PI-CNA are studied
Raw materials and Preparation:
Flexible carbon nanofiber aerogel (PI-CNA) was prepared using electrospun polyimide aerogel as raw material.
Features of PI-CNA:
Lightweight piezoresistive sensor: Wide linear range (0-217 kPa), fast response/recovery time, fatigue resistance (12,000 cycles).
Multi-functional applications:
This includes a full range of healthcare sensing, such as pulse monitoring, physiological activity detection, speech recognition and gait recognition.
Electromagnetic interference (EMI) shielding effect
The EMI shielding efficiency (SE) reached 45 dB and the A-coefficient was 0.62, indicating an excellent EMI shielding effect based on absorption.
Joule heating performance:
At a low supply voltage of 1.5-5 V, the PI-CNA has a Joule heating performance of up to 120°C and a fast response time of 10-30 seconds.
It shows good heating reliability and repeatability in long-term repeated heating/cooling cycles
In summary, we demonstrate a lightweight PI-CNA with full range of healthcare sensing, electromagnetic interference shielding, and multiple functions for joule heating through moisture-induced electrospinning and carbonization. Pi-cna-based sensors offer excellent sensing performance, wide linear range (0-217 kPa), fast response/recovery time (230/120 ms) and high durability (12,000 cycles). In addition, to determine the capabilities of the PI-CNA sensor for wearable applications, a full range of physical activity monitoring was performed, such as pulse, joint bending, expression, breathing, vocal cord vibration, and gait recognition. Thanks to the special conductive network, the PI-CNA also exhibits an excellent EMI shielding performance of 45 dB and A high A value of 0.62, indicating that it has an excellent absorption-oriented EMI shielding mechanism due to multiple reflections and internal absorption effects. In addition, the PI-CNA has excellent Joule heating capacity, heating temperatures up to 120 °C at 5 V supply voltage, rapid heating and cooling response, and excellent operating stability. Due to its versatility, the PI-CNA wearable gadget is expected to offer significant advantages in the areas of health monitoring, electromagnetic protection and Joule heating treatment.
