An ultrasensitive three-dimensional structured multi-mode sensor for out-of-plane forces

This work presents an ultrasensitive three-dimensional (3D) structured sensor with out-of-plane tactility and non-contact perception capabilities. It is composed of flexible silver nanowire-patterned magnetic film and the printed heat-responsive polymer skeleton by means of spin-coating, masking, and printing technologies. Besides the capabilities in detecting tension, compression, shear, and even air vibration/flow, the 3D-structured sensor also exhibits the advantages of prompt response, super flexibility, outstanding sensitivity, high reversibility and stability. The responsive relative resistance variations of the 3D-structured sensor exhibit an excellent linear relationship with the pull-out/press-in forces, and the sensitivities are estimated as 21.8 % N−1 and −19.6 % N−1, respectively. Furthermore, it is demonstrated that the applied direction and strength of shear excitation can be well predicted via applying machine learning methods. Moreover, the sensor is able to clearly detect the loading paths of external excitations, including the load waveform and even the initial phase. Notably, the normalized resistance of the sensor changes with the magnetic flux density which is promising in tuning the sensitivity of the sensor within a magnetic field. The exceptional multi-mode sensing characteristics demonstrate that the 3D-structured sensor possess great potentials for implementation in next-generation smart devices or systems.