In this paper, we present our study on developing a P(VDF-TrFE) pressure sensor for the application of small strain sensing. P(VDF-TrFE) has an excellent chemical resistance, biocompatibility, flexibility, electrostatic and piezoelectric characteristics. It can be applied for personalized health monitoring, such as heart rate and blood pressure monitoring. To measure the small strain generated by a soft tissue, we develop a flexible pressure sensor based on highly aligned electrospun P(VDF-TrFE) micro-fibers. Both electrostatic and piezoelectric sensing methods were studied. We use a drum collector to create a highly aligned fibers, and use annealing and corona discharge to enhance β phase of P(VDF-TrFE) fibers. The electrodes that we design was 10 mm square, and sensitivities of electrostatic and piezoelectric signals were studied. A 4-point bending test was used to perform small strain measurement. Our experimental finding demonstrated that the sensitivity of sensor with fibers in parallel with bending direction was 5.39 × 10−2 𝑝𝐴/με., The sensitivity of sensor with fibers in perpendicular with bending direction was 2.38 × 10−2pA/με. The sensitivity of parallel fibers was 2.26 times higher than the perpendicular fibers. Furthermore, we verified that after removing electrostatic charges in the P(VDF-TrFE) membrane, the major contribution of the parallel aligned sensor was piezoelectric effect. The P(VDF-TrFE) pressure sensor has about 80% of piezoelectric effect and about 20% of electrostatic effect. On the other hand, both electrostatic and piezoelectric properties contribute to the sensitivity in perpendicular aligned pressure sensor.
Zi-Yi Zheng, Jun-Yi Ke, Yu-Hsiang Hsu, and Chih-Kung Lee, "Electrospun unidirectional P(VDF-TrFE) pressure sensor for small strain sensing," Proc. SPIE 10597, Nano-, Bio-, Info-Tech Sensors, and 3D Systems II, 105970F (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 06, 2018; Published: 10 April 2018); https://doi.org/10.1117/12.2296687.
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