Tactile sensors that mimic the human sense of touch are widely used in robotics, human–computer interaction, advanced prosthetic design, and medical monitoring [1]. These sensors are capable of detecting external stimuli, such as pressure and multidimensional force, making them essential for applications requiring precise manipulation and intelligent interaction. To meet diverse sensing needs and suit different application scenarios, tactile sensors employ various sensing principles, including the strain gauge [2], [3], capacitive [4], [5], piezoelectric [6], [7], and optical fiber [8], [9], [10], [11]. Among these, optical fiber based sensors stand out due to their small size, immunity to electromagnetic interference, high accuracy, robustness, and superior physical and chemical stability [12], offering a promising approach for advancing tactile sensing.

Fiber Bragg gratings (FBG) are commonly employed as tactile sensing elements [13]. For example, Qin et al. [14] developed a two-range tactile sensor based on FBG, which was designed by nesting two elastomers. It achieved a wide range of 0–50 N and maximum sensitivity of 0.03 nm/N. Additionally, various techniques involving fiber coating or doping have been successively reported. Celeste et al. [15] proposed a tactile sensor where a coated elastomeric waveguide detects pressure through light-modulating microcracks, achieving a high sensitivity of 3.5e-5μW/kPa. Liu et al. [16] presented an optical fiber flexure hinge based on lateral doping bend enhanced optical fiber, which establishes a correlation between scattering loss and both bending deformation and direction. However, these reported tactile sensors rely on the use of specialty optical fibers, which poses significant demands on the sensor fabrication process.

To address these fabrication challenges, some studies have employed standard optical fibers and adjusted their force sensitivity through structural design, offering advantages such as low cost and simple fabrication. Chen et al. [17] developed a soft tactile sensor based on a two-layered anisotropic optical fiber structure, which is capable of decoupling and measuring three-dimensional forces. Within a range of 0–2 N, the average accuracies for Fx, Fy, and Fz were 0.17 N, 0.18 N, and 0.15 N, respectively. Inspired by the topological mechanics of knots, Pan et al. [18] developed a tactile sensor based on a knotted optical fiber structure. The knot provides anisotropic responses to decouple normal and friction forces. With a knot diameter of 2.5 mm, the sensitivity to normal force was calculated to be 2.67 N−1, and the corresponding friction force sensitivity was 6.36 N−1 under preloaded normal forces of 7.5 N. Li et al. [19] proposed a tactile sensor utilizing coiled multimode polymer optical fiber with a three dimensional spring-like architecture. The sensor with 8.5 coils has a sensitivity of 21.1 N−1 within the range of 0–2 N.

In this paper, a fiber tactile sensor based on a double helix structure is presented. The double helix structure amplifies the bending-induced optical loss, making it sensitive to external force. The experimental results show that the tactile sensor has a sensitivity of −26.2 N−1 and can measure force in the range of 0–3 N. Furthermore, the sensitivity and measurement range may be adjusted by altering the number of turns and the diameter, indicating that the sensor has considerable design freedom. The sensors were ultimately incorporated into a multidimensional force sensing system and successfully distinguished between the different components of the multidimensional force acting on the system. These results verify the feasibility of the double helix structure sensor (DHSS) in multidimensional force detection. Its excellent sensitivity and straightforward production suggest considerable potential for practical applications in tactile sensing.