Flexible six-dimensional force sensor inspired by the tenon-and-mortise structure of ancient Chinese architecture for orthodontics

Precise multi-axis operation is essentially required in orthodontics for tooth movement. Despite the development of flexible multi-dimensional force sensors that have effectively perceived multi-dimensional forces, they still face the challenge of simultaneously 3D force and moment in a single flexible force sensor. Six-dimensional force perception can successfully operate objects that critically rely on directional tracking and accurate monitoring of complex multi-axis stimuli. To realize the integration of sensing units with the perception of six-dimensional force under even a soft touch, we design a flexible six-dimensional force sensor with tenon-and-mortise interlocking structures inspired by traditional Chinese ancient architecture. This unique structure enables conjunction of deformation, which can be studied and decoded by Deep Neural Networks (DNN) with six-dimensional force, including forces and rotating moments in the x, y, and z directions. This soft sensor with minimal size (7 × 7 × 7 mm3) and high detection accuracy (the DNN error is below 10−4) can be used in orthodontic treatment for precise correction with a full collection of orthodontic force. This unique flexible six-dimensional force sensor provides a new strategy for the design of multi-dimensional force sensors, paving the way for the development of intelligent robotics, interactive human-machine interfacing, and advanced prosthetics.