Humanoid robots are envisioned as general-purpose platforms in human-centered environments, yet their deployment is limited by vulnerability to falls and the risks posed by rigid metal-plastic structures to people and surroundings. We introduce a soft-rigid co-design framework that leverages non-Newtonian fluid-based soft responsive materials to enhance humanoid safety. The material remains compliant during normal interaction but rapidly stiffens under impact, absorbing and dissipating fall-induced forces. Physics-based simulations guide protector placement and thickness and enable learning of active fall policies. Applied to a 42 kg life-size humanoid, the protector markedly reduces peak impact and allows repeated falls without hardware damage, including drops from 3 m and tumbles down long staircases. Across diverse scenarios, the approach improves robot robustness and environmental safety. By uniting responsive materials, structural co-design, and learning-based control, this work advances interact-safe, industry-ready humanoid robots.
@article{arxiv.2601.02857,
title = {Soft Responsive Materials Enhance Humanoid Safety},
author = {Chunzheng Wang and Yiyuan Zhang and Annan Tang and Ziqiu Zeng and Haoran Chen and Quan Gao and Zixuan Zhuang and Boyu Li and Zhilin Xiong and Aoqian Zhang and Ce Hao and Siyuan Luo and Tongyang Zhao and Cecilia Laschi and Fan Shi},
journal= {arXiv preprint arXiv:2601.02857},
year = {2026}
}