Bioinspired growable humanoid robot with bone-mimetic linkages for versatile mobility

Inspired by human biomechanics, humanoid robots are often designed to mimic human kinematics but typically lack key traits of developing bones, such as growability, lightweight yet stiff construction, and compliance for impact absorption. This work introduces a bone-inspired linkage structure with up to 315% extensibility, weighing only 350 grams while maintaining high load capacity, compliance, and stability. Integrated into a soft humanoid robot, these growable linkages enable dynamic shape adaptation, reducing height to 36% and width to 61%, to traverse tight spaces. By combining growable link actuation with servomotors, the robot switches to crawling mode and moves 1122 times faster than using motors or soft actuators alone. At just 4.5 kilograms, GrowHR can float, swim, walk on water, and fly. Its soft body ensures safe human interaction, allowing hugging, falling, and lifting without injury. Deformable legs demonstrate elastic energy storage and release under external loading, allowing motions beyond the limits of rigid structures. This work pioneers a growable, multifunctional robotic design approach for dynamic, complex environments.