Remote tactile sensing through optical fibers for robotics in extreme environments: a review

The advancement of intelligent robotic systems has driven increasing demand for tactile sensing technologies capable of reliable operation in extreme environmental conditions where conventional electronic sensors often fail due to electromagnetic interference, high temperatures, corrosive chemicals, or ionizing radiation. Optical fiber-based tactile sensors offer a promising alternative, combining electromagnetic immunity, high sensitivity, multiplexing capability, and mechanical resilience. These characteristics make them well suited for remote sensing tasks in challenging operational scenarios. Although several reviews have discussed optical fiber sensing technologies, limited attention has been given to their integrated application in tactile sensing for robotic systems operating under extreme environmental conditions, particularly with respect to emerging functional materials, harsh-environment adaptability, and next-generation intelligent robotic platforms. This review presents a comprehensive analysis of recent progress in optical fiber tactile sensing, focusing on robotics applications operating under extreme environmental conditions. We first outline the fundamental sensing mechanisms—namely, Fiber Bragg Grating (FBG), Fabry–Perot Interferometry (FPI), light intensity modulation, speckle pattern analysis, and surface plasmon resonance (SPR), and assess their performance in detecting force, pressure, temperature, and vibration. Subsequently, we examine advances in sensor materials, encompassing silica and polymer optical fibers (POFs), as well as emerging platforms based on hydrogels and micro/nanofibers (MNFs). Emphasis is placed on developments that enhance flexibility, stretchability, biocompatibility, and self-healing performance. These material innovations significantly expand the potential for deploying optical tactile sensors in dynamic and unstructured environments. The review further explores real-world applications where optical fiber tactile sensing has demonstrated impact, including minimally invasive surgical instruments, industrial automation systems, subsea exploration, extraterrestrial robotics, and disaster response operations. In each case, the ability to deliver accurate and high-resolution tactile feedback in harsh conditions is critical for safe and precise robotic manipulation. Emerging research directions are discussed, including the integration of artificial intelligence for tactile data processing, the development of bioinspired swarm robotic systems, and the implementation of self-adaptive and distributed sensing networks. Finally, we highlight critical challenges, such as signal drift, sensor miniaturization, packaging strategies, and long-term environmental stability, and propose future research pathways to support scalable, robust deployment. By providing a structured overview of current technologies, applications, and research challenges, this review aims to serve as a foundational reference for researchers and engineers advancing high-performance tactile sensing in extreme robotic environments.