A Chemically Driven Soft Growing Robot with Coupled Gas Generation and Growth Dynamics

Soft growing robots achieve extension through material eversion and exhibit remarkable compliance and adaptability in confined environments. However, most existing soft growing robots still rely on tethered laboratory pneumatic supplies, onboard electric compressors, or pre-charged gas reservoirs for actuation. In contrast, chemical reaction--based actuation for soft growing robots remains largely unexplored. Inspired by the internally driven tip-growth process observed in biological systems such as pollen tubes, this work presents a chemically driven soft growing robot in which gas generated on demand from liquid reactants replaces a conventional compressed-gas supply. To quantitatively characterize {the relationship between chemical gas generation and eversion-based growth, a gas-generation--pressure--growth model is developed by linking supply-dependent gas generation, pressure evolution, growth-induced cavity expansion, and eversion mechanics. The model elucidates the relationship between gas generation and robot elongation, enabling predictable regulation of growth velocity and startup time through reactant concentration and liquid-feed-rate control. Experimental results demonstrate efficient and stable growth performance. The measured growth velocity, internal pressure, and startup time agree closely with theoretical predictions, validating both the proposed actuation strategy and the developed model within the tested operating conditions. The presented framework establishes a biologically inspired approach to internally actuated soft growing robots and provides a foundation for the future development of more self-contained growing robotic systems, while the present study focuses specifically on chemically generated pneumatic actuation and growth dynamics.