Flexible tactile sensors demonstrate significant potential for applications in robotics, human-computer interaction, advanced prosthetic design, and medical monitoring. In robotic systems, the ability to detect both contact force and its position is essential for effective object manipulation. While electrically based flexible tactile sensors have been extensively researched over the past decade, their practical implementation faces challenges including high manufacturing costs, parasitic effects, complex circuits, and signal crosstalk. Optical sensing schemes have emerged as a promising alternative, with optical waveguide/fiber-based tactile sensors garnering particular attention. Initially, optical fiber Bragg gratings were employed for tactile sensing. However, the inherent brittleness and limited flexibility of silica-based optical fibers restrict their integration onto curved surfaces and spatial resolution capabilities. Polymer optical waveguides/fibers present enhanced flexibility, enabling seamless integration into curved surfaces and flexible structures, thus offering a more effective tactile sensing solution. This study proposes a flexible dual-core multimaterial optical waveguide tactile sensor featuring a multilayered structure with distinct cores for force detection and position discrimination. To address existing challenges, this research develops a distributed flexible dual-waveguide tactile sensor utilizing induced loss blocks.

Leveraging the advantages of polymer optical waveguides, this research develops a distributed flexible dual-waveguide tactile sensor based on induced loss blocks through total internal reflection theory. The multilayer composite structure physically isolates force/position signals, effectively eliminating crosstalk. The integration of fiber thermal drawing technology in waveguide fabrication enables cost-effective mass production while maintaining excellent flexibility and structural reliability.

The tactile sensor implements a multi-layer composite structure, as illustrated in Fig. 1. The design incorporates differentiated upper and lower waveguide structures to achieve decoupled measurement of contact force magnitude and position. The upper waveguide comprises a uniform rectangular cross-section with core and cladding layers, while the lower waveguide integrates rectangular loss-inducing block arrays into the conventional cladding-core configuration. The sensor's measurement principles were theoretically derived using total internal reflection theory and Lamé equations. Numerical simulations utilizing the beam propagation method (BPM) analyzed the optical field distribution characteristics of the lower waveguide core and output power attenuation profiles versus propagation distance (Fig. 2). The analysis examined the relationship between output light intensity and both loss-inducing block width and material refractive index (Fig. 4). Through the combination of fiber thermal drawing technology and conventional molding methods (Fig. 5), a flexible dual-waveguide tactile sensor of 70 mm×5 mm×3.5 mm was successfully fabricated (Figs. 6 and 7). Comprehensive performance testing (Figs. 9?11, Fig. 13, and Fig. 14) demonstrated 6 mm spatial resolution and 1 N stress resolution for contact force position and magnitude measurements. The sensor exhibits a wide dynamic measurement range (0?8 N) with excellent dynamic response characteristics. During extended cyclic loading, signal attenuation remained below 5%, with optical output baseline drift rate smaller than 0.008 h^-1. After 3000 loading cycles, the sensor maintained structural integrity without surface cracks, plastic deformation, or delamination.

This research presents the development and fabrication of a distributed flexible dual-waveguide tactile sensor utilizing induced loss blocks through total internal reflection theory. The multilayer composite structure enables simultaneous dual-parameter measurement of contact force position and magnitude without crosstalk. The fabrication process combines fiber thermal drawing technology with conventional molding methods to produce a flexible dual-waveguide tactile sensor of 70 mm×5 mm×3.5 mm. The sensor achieves 6 mm spatial resolution and 1 N stress resolution for position and magnitude measurements, with a dynamic range of 0?8 N and superior dynamic response. Testing over 3000 cycles demonstrated performance degradation below 5% without structural deterioration. The sensor design offers cost-effective, batch-reproducible fabrication with array integration compatibility. Further optimization of materials, structural design, and manufacturing processes can enhance mechanical performance and resolution capabilities.