Flexible multidimensional sensor for comprehensive human motion monitoring and recognition

Abstract

Flexible multidimensional sensors are essential for smart wearables in motion monitoring, recognition and health tracking. However, conventional strain sensors have limitations for application in complex three-dimensional (3D) motion analysis due to their tradeoff between the detection direction and strain sensitivity, and the process compatibility for system integration in flexible sensors. This work presents a novel flexible multidimensional sensor capable of simultaneous detection of in-plane (along X- and Y-axes) and out-of-plane pressure (Z-axis) strain direction using an integrated thin film sensor. The 3D thin film sensor comprises a tri-layer structure of an upper pressure sensor component and a stack of orthogonally aligned nanofibrous strain layers, forming a cross-structured sensor with strong orthogonally directional selectivity. The integrated 3D thin film sensor is fabricated by electrospinning and infiltration, achieving a high gauge factor (GF) of 925 and a wide strain range of 630%. The sensor exhibits an in-plane GF of 293.2 along the X-axis and that of 1.3 along the Y-axis, yielding a high selectivity ratio of 6.15, revealing a mechanical stability over 5500 cycles with minimal crosstalk. It accurately distinguishes strain direction (0°–90°) and magnitude. Z-axis pressure is detected via a capacitive mechanism, thus enabling full 3D force perception. Integrated with a long short-term memory network, the 3D sensor achieves 95.83% accuracy in recognizing complex motions, surpassing single-axis recognition by 21.7%. This work demonstrates a compact, high-performance approach to multidimensional sensing for intelligent wearable motion monitoring and recognition systems.

Keywords

3D mechanical sensing / flexible multidirectional sensor / motion monitoring and recognition / orthogonal stacked fibrous films

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2026 The Author(s). FlexMat published by John Wiley & Sons Australia, Ltd on behalf of Nanjing University of Posts & Telecommunications.