Development of multi-directional piezoelectric sensor doped with graphene by near-field electrospinning technology for calligraphy writing

A novel multi-directional (MD) circular-shaped fiber piezoelectric sensor was developed to detect calligraphy writing force from various directions quantitatively. The sensor was fabricated using polyvinylidene fluoride (PVDF) piezoelectric fibers doped with Graphene and spun using direct-write near-field electrospinning (NFES) technology. The NFES collector, designed as a rotating disc system, orderly collected the fibers to enhance the piezoelectric effect and dipole moments, forming the circular sensor. Flexible electrical electrodes with multiple signal output circuits were incorporated for calligraphy stroke sensing, bonded with circular PVDF fibers to create the flexible MD sensor. With inner and outer diameters of 20mm and 60mm, the circular sensor responded to deformable signals induced by calligraphy strokes. Parameters of sensor fabrication were optimized using the uniform design experimental method. Calibration involved tapping tests at 1-10Hz to correlate fiber output voltage with the corresponding force. The single sensor reached a maximum voltage output of approximately 908mV and detected forces ranging from 0.1 to 50N. After validating the MD circular-shaped piezoelectric sensor, a 3x3 sensor array was configured for calligraphy writing force sensing, providing quantitative measurements of dynamic responses during writing, valuable as a data source for apprentice learning.