A Comprehensive Review of Emerging Flexible Tactile Sensors: Mechanisms, Nanomaterials, Microstructures and...

Flexible tactile sensors represent pivotal physical interfaces for human-machine interaction and embodied intelligence. However, the inherent trade-offs between sensitivity and sensing range, multimodal crosstalk, and long-term biosafety remain critical bottlenecks hindering practical implementation. This work adopts a "Material-Microstructure-Application" pipeline to categorize and analyse recent advancements developed in response to technical challenges. The review first delineates mainstream sensing mechanisms, followed by an analysis of the intrinsic physical properties and modification strategies of carbon/metal-based nanomaterials, emerging MXenes, and composite hydrogels. Specifically, a critical assessment of the biosafety and toxicological risks associated with functional nanomaterials in long-term wearable and implantable scenarios is conducted, bridging a notable gap from the perspective of clinical translation. Building upon these material foundations, the role of surface micro-engineering, consisting of biomimetic interlocking and porous architectures, in surpassing performance limits through the fine-tuning of contact mechanics is discussed. Furthermore, the potential of flexible manufacturing techniques, such as 3D printing and laser direct writing, to overcome the constraints in complex 3D architecting and scalable fabrication is summarized. Eventually, frontier applications in medical monitoring and robotic perception are exhibited, with a focus on the empowerment of machine learning-assisted signal classification, multimodal recognition, and inverse design. This review aims to provide comprehensive theoretical insights for the development of next-generation tactile sensing systems characterized by high biocompatibility and spatiotemporal resolution.