A Spider Leg-Inspired mm-Scale Soft Exoskeleton Enabled by Liquid via Hydration and Charge Transport

In organisms, liquid as a continuum intertwines architected components (organs), including nervous, vascular, and musculoskeletal systems. In this regard, spiders exhibit remarkable embodiments where hemolymph, which infuses the animal, simultaneously enables muscle activation and exoskeleton compliance. Previous works on spider-inspired artificial systems have focused on disentangled aspects, such as pressurization and flexible structures, yet organism-like liquid-mediated physical intelligence integrating control, distribution of resources, actuation, and support is still to be demonstrated. Here a spider-leg-inspired soft exoskeleton integrating a muscular system is shown, enabled by the contained liquid through hydration for compliance conditioning and charge transport for muscle activation. A two-photon polymerized 0.8 mm-diameter exoskeleton is reported that contains an electrolyte solution and is actuated via contraction of an ionic electroactive polymer muscle operated at 0-1 V. The exoskeleton features reversible bending and compliant interaction with natural entities such as anthers, spider webs, and pollen grains. The reported technology demonstrator, which functionally intertwines muscularization, vascularization, and innervation via liquid, supports the development of liquid-enabled systems based on embodied energy and multi-material design, particularly for bioinspired soft robotics. Natural organisms feature an unrivaled intertwining between structure and function via the bodily integration of multiple phases, multifunctional materials and architected elements. Learning from this, this study unveils a spider-leg-inspired artificial embodiment where the internal electrolyte simultaneously enables compliance conditioning via hydration, and charge transport for muscle activation. The achieved results support the development of liquid-enabled bioinspired soft robotics systems. image