Flexible capacitive pressure sensor based on expandable microsphere/ polydimethylsiloxane composite dielectric layer
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摘要: 为解决含有微结构的柔性电容式压力传感器工作范围较窄的问题，设计了一种基于可膨胀微球/聚二甲基硅氧烷(PDMS)介电层的柔性“三明治”结构电容式压力传感器，并对介电层的结构和形貌进行表征。通过自行搭建的压力设备和电容采集设备研究了基于可膨胀微球/PDMS介电层传感器的力学性能和电学性能。结果表明：通过向PDMS介电层中加入可膨胀微球显著降低了介电层的杨氏模量，同时提高了压力下介电层的介电常数，可膨胀微球/PDMS介电层传感器的工作范围可达400 kPa，最大灵敏度达到0.06 kPa−1，在100 kPa的负载循环下具有较好的重复性和稳定性，且具有较低的迟滞性(4.7%)，可以准确迅速地检测到指尖压力，在生命健康等领域具有潜在的应用前景。Abstract: In order to solve the problem of narrow working pressure range of microstructured flexible capacitive pressure sensors, a flexible “sandwich” structure capacitive pressure sensor based on expandable microsphere/polydimethylsiloxane (PDMS) dielectric layer was designed in this paper. Then the structure and morphology of the expandable microsphere/PDMS dielectric layer were characterized. The mechanical and electrical properties of the expandable microsphere/PDMS dielectric layer sensor based on expandable microsphere/PDMS dielectric layer were tested by self-built pressure and capacitance acquisition equipment. The results show that the Young’s modulus of the expandable microsphere/PDMS dielectric layer is significantly reduced due to the addition of expandable microsphere into PDMS, and the dielectric constant of the expandable microsphere/PDMS dielectric layer is increased under pressure. The working pressure range of the expandable microsphere/PDMS dielectric layer sensor is up to 400 kPa, and the maximum sensitivity reaches 0.06 kPa−1. The expandable microsphere/PDMS dielectric layer sensor has good repeatability and stability under the load cycle of 100 kPa, and low hysteresis (4.7%). It can detect fingertip pressure accurately and rapidly, which has potential applications in areas of life and health.
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Key words:
- capacitive pressure sensors /
- polydimethylsiloxane /
- porous materials /
- fabrics /
- sensitivity
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图 2 可膨胀微球/聚二甲基硅氧烷(PDMS)介电层制备流程示意图
Figure 2. Preparation diagram of expandable microsphere/polydimethylsiloxane (PDMS) dielectric layer
图 4 可膨胀微球/PDMS介电层和纯PDMS介电层的SEM图像
Figure 4. SEM images of expandable microsphere/PDMS dielectric layer and PDMS dielectric layer
图 5 可膨胀微球/PDMS-1介电层和纯PDMS介电层的FTIR图谱
Figure 5. FTIR spectra of expandable microsphere/PDMS-1 dielectric layer and PDMS dielectric layer
图 6 可膨胀微球/PDMS-1介电层和纯PDMS介电层的XRD图谱
Figure 6. XRD patterns of expandable microsphere/PDMS-1 dielectric layer and PDMS dielectric layer
图 7 不同微球含量时可膨胀微球/PDMS介电层传感器的灵敏度随加热时间的变化
Figure 7. Sensitivity of expandable microsphere/PDMS dielectric layer sensors as a function of heating time with different contents of microspheres
图 8 不同微球含量的可膨胀微球/PDMS介电层传感器的力学性能
Figure 8. Mechanical properties of expandable microsphere/PDMS dielectric layer with different contents of microspheres
图 9 可膨胀微球/PDMS-1和PDMS介电层传感器的灵敏度
Figure 9. Sensitivity of expandable microsphere/PDMS-1 and PDMS dielectric layer sensors
ΔC—Difference capacitance of sensor; C0—Initial capacitance of sensor
图 10 可膨胀微球/PDMS介电层传感器的重复性
Figure 10. Repeatability of expandable microsphere/PDMS dielectric layer sensor
图 11 可膨胀微球/PDMS介电层传感器的稳定性
Figure 11. Stability of expandable microsphere/PDMS dielectric layer sensor
图 12 可膨胀微球/PDMS介电层传感器的迟滞性
Figure 12. Hysteresis of expandable microsphere/PDMS dielectric layer sensor
图 13 不同条件制备的可膨胀微球/PDMS介电层传感器的电容变化率曲线
Figure 13. Capacitance change rate curves of expandable microsphere/ PDMS dielectric layer sensors prepared under different conditions
图 14 手指按压时可膨胀微球/PDMS介电层传感器的电容变化率曲线
Figure 14. Capacitance change rate curve of expandable microsphere/ PDMS dielectric layer sensor by finger pressing
图 15 鼠标点击时可膨胀微球/PDMS介电层传感器的电容变化率曲线
Figure 15. Capacitance change rate curve of expandable microsphere/ PDMS dielectric layer sensor by mouse clicking
表 1 不同电容式压力传感器的灵敏度对比
Table 1. Sensitivity comparison of different capacitive pressure sensors
Electrode Dielectric layer Sensitivity/kPa−1 Ref. Carbon nanotube (CNTs) Ecoflex 0.00059 [28] Silver nanowire (AgNW) PDMS 0.00040 [29] Conductive knitted fabrics Microporous silicone elastomer 0.01210 [7] Multiwall carbon nanotubes (MWNTs) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) composite electrodes Porous PDMS 0.00112 [30] CNTs yarn Ecoflex 0.05000 [31] Indium tin oxide (ITO)/polyester (PET) Microstructured PDMS 0.05500 [32] AgNW Ecoflex 0.00162 [33] Conductive woven fabrics Expandable microsphere/PDMS 0.06000 This work 
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