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Professor Wu Dezhi (Xiamen University): High-Performance Flexible Capacitive Pressure Sensor Based on Spiked Ni/PI Composite Nanofiber Membranes
In recent years, flexible pressure sensors have been applied in health monitoring, human-machine interaction, smart prosthetics, and electronic skin. With advancements in IoT, Industry 4.0, big data, AI, robotics, and digital health, their applications are expanding, especially in complex scenarios. However, the sharp increase in compressive modulus of sensor dielectric layers under high pressure drastically reduces sensitivity, limiting practical use. Thus, developing flexible pressure sensors with wide-range detection, high sensitivity, and fast response/recovery is urgently needed.
Recently, Professor Wu Dezhi's research team at Xiamen University published their latest research findings titled "High-performance flexible capacitive pressure sensor based on a spiked nickel/polyimide composite nanofiber membrane" in the journal ACS Sensors. The researchers designed a capacitive flexible pressure sensor based on a composite nanofiber membrane of metal particles and polymer, which can operate stably over a wide pressure range of 1.5 MPa.
Using an electrostatic self-assembly method, spiked Ni particles were adsorbed into the porous polyimide nanofiber membrane to construct a spiked Ni/PI composite nanofiber dielectric layer. Compared to pure polyimide nanofiber membranes, the sensor's sensitivity was improved by more than 4 times. A small-sized, expandable capacitive array sensor and its acquisition system were also designed.
Experimental results showed that the sensor exhibited long-term stability of over 1000 cycles and fast response/recovery times (30/40 ms). Due to its excellent performance, the sensor can be applied in many scenarios such as human motion detection, sleep posture monitoring, and plantar pressure measurement, demonstrating good application prospects in various wearable systems.
Figure 1: Sensor structure, working principle and manufacturing process.
Manufacturing process: After preparing the nanofiber membrane by electrospinning, circular membranes of the required size were obtained by UV laser cutting. Patterned epoxy resin adhesive was then printed on the upper and lower electrodes using screen printing. The nanofiber membrane was placed between custom compression electrode plates, kept pressed until the adhesive cured, finally constructing the dual-point flexible pressure sensor shown in Figure 1d.
Figure 2: Preparation method of spiked Ni/PI nanofiber membrane.
The spiked Ni particles and PI nanofiber membrane were separately placed in CTAB solution and SDS solution. The PI nanofiber membrane was then placed in CTAB solution. Through anion and cation adsorption, spiked Ni particles were observed to adsorb between the nanofiber membranes, resulting in the spiked Ni/PI composite nanofiber membrane.
Figure 3: Sensing performance of flexible pressure sensor based on spiked Ni/PI composite nanofiber membrane.
Figure 4: Application of capacitive flexible pressure sensor in health monitoring.
Figure 5: Practical application of small-sized flexible pressure sensor array in plantar pressure detection.
Experimental results showed that sensors prepared by this method had good sensing performance, with fast response/recovery times of 30/40 ms, pressure detection range of ~1.5 MPa, and excellent mechanical stability after 1000 cycles at 500 kPa. Furthermore, by designing scalable sensor arrays, customized solutions can be developed for various pressure monitoring applications, such as human motion detection, sleep posture monitoring and plantar pressure monitoring.
