A Soft, Insect-Inspired, Distributed Tactile Sensor Enables Effective Touch Perception

Insects navigate cluttered environments using slender, flexible antennae densely packed with mechanosensors, a lightweight, energy-efficient solution for tactile perception. We introduce CITRAS (Cockroach-Inspired Tactile Robotic Antenna Sensor), a miniature, compliant, multi-segment tactile probe aimed at enabling similarly capable close-range perception on insect-scale robots under stringent size, mass, and power constraints. CITRAS (total size:$\hspace{0.17em}73.7\hspace{0.17em}\times \hspace{0.17em}15.6\hspace{0.17em}\mathrm{mm}\hspace{0.17em}\times \hspace{0.17em}2.11\hspace{0.17em}$mm; mass: $491\hspace{0.17em}\mathrm{mg}$) features eight flexural hinge segments, each with high-resolution capacitive sensors embedded within a compliant multilayer laminate structure, that detect femtofarad-scale capacitance changes induced by hinge deflection. Through systematic mechanical and sensing characterization under both quasi-static and dynamic conditions, we demonstrate sub-degree angular precision (max error $\mathrm{\le \hspace{0.17em}}0.8$∘), accurate shape reconstruction, and consistent repeatable performance with minimal hysteresis in slow bending. Under rapid interactions, CITRAS exhibits low damping and rich dynamic responses that encode environmental features. We further validate the system in three core tactile tasks: estimating body-to-wall distance (error $\mathrm{\le \hspace{0.17em}}8\%$), measuring object gap width (error $\mathrm{\le \hspace{0.17em}}7\%$), and discriminating between smooth and rough surface textures via spatiotemporal tactile images. These results show that CITRAS delivers a compact, distributed, bioinspired tactile modality capable of reliable environment sensing, filling a critical gap in perception for insect-scale robots. Furthermore, the antenna consumes only $32\hspace{0.17em}\mathrm{mW}$ (excluding MCU), making it suitable for future full deployment onboard insect-scale robots and thus paves the way for autonomous navigation and interaction in confined, unstructured, or delicate environments at this scale.