A flexible 3D force sensor for handwriting recognition

This paper proposes a high-sensitivity flexible pressure sensor with three-dimensional force detection function, which has broad application prospects in artificial intelligence, tactile sensing, and electronic equipment. Our flexible three-dimensional force consists of two flexible cotton layers with conductive patterns and a dielectric elastic film with porous structure. Four parallel plate capacitors are realized on the porous elastic film. Under the action of the normal force, the porous structure elastic film is compressed, the distance between the two patterned electrodes is reduced, and the micropores are compressed, resulting in the change of dielectric constant, so the capacitance changes. Under the tangential force, the porous dielectric elastic film deforms, which causes the overlap area of the upper and lower patterned electrodes to change, which causes the change of capacitance. This study compares the Young's modulus of the porous structure elastic film with the solid film, which reflects that the porous structure elastic film is more prone to deformation. The minimum detectable force and response/recovery time experiments have also been carried out, and our sensors show good detection limits and response time. In addition, applying contact forces in different directions to the sensor can get different capacitance outputs, indicating that our sensors can distinguish forces in different directions. Finally, we made the sensor into a pen for handwriting recognition on different rough surfaces.