A Highly Sensitive and Self-Decoupled Flexible Capacitive Ionic 3-D Force Sensor for Human–Machine Interactions

-in recent years, flexible three-dimensional (3D) force sensors have played a significant role in human-machine interaction due to their excellent compatibility with curved surfaces and multi-axis force detection capabilities. However, they generally suffer from inadequate sensitivity and severe signal coupling challenges. To address these limitations, this study introduces a flexible three-dimensional force sensor based on ionic capacitance, offering inherent signal decoupling and improved sensitivity. The sensor architecture utilizes PVC gel as the dielectric medium, harnessing the electric double-layer effect, while ionic liquid doping is employed to enhance dielectric performance. Additionally, a vertically orthogonal electrode configuration enables efficient decoupling of 3D force components. The sensor demonstrates outstanding performance, including high directional sensitivity (5.80 N^-1 normal, 2.39 N^-1 tangential), fast dynamic response (response/recovery: 120/140 ms), and excellent durability (over 1200 cycles). The sensor is also capable of detecting forces as low as 0.1 N, indicating high resolution and responsiveness to subtle pressure changes. Finally, the sensor was successfully applied to the field of human-machine interaction applications including remote handle control, robotic grasping and humanoid motion monitoring. The sensor’s high sensitivity and self-decoupling mechanism enable accurate detection of multi-axial force components, making it ideal for human–machine interfaces.