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Humanoid robots are often promoted as versatile helpers, but in real-world conditions they remain constrained by rigid frames and limited mobility. Tight spaces, uneven terrain, water obstacles, and debris-filled environments quickly expose the weaknesses of conventional designs. For search and rescue, inspection, or disaster response, robots need to adapt their shape and movement as easily as humans do.
A newly demonstrated soft humanoid robot (GrowHR) offers a different approach. Instead of relying on fixed, column-like structures, the robot uses growable, bone-inspired linkages that allow it to change size, shape, and mode of movement on demand. The result is a lightweight platform that can extend, compress, crawl, float, swim, and even move across water.
At the core of the design are expandable structural elements that combine soft chambers, tensioned cables, and rigid connectors. These linkages can lengthen by more than three times their original size while maintaining stability and load-bearing capability. A non-stretchable outer layer provides axial stiffness, while synchronized cable control ensures smooth and uniform motion. Each linkage weighs only a few hundred grams, keeping the full robot’s weight under 4.5 kgs.
According to Interesting Engineering, this architecture allows the humanoid to dramatically alter its dimensions. It can nearly triple its height to reach elevated areas, then shrink its profile to pass through narrow gaps. By coordinating its extendable structures with joint-mounted motors, the robot achieves efficient crawling speeds far beyond what either system could deliver alone. Its lightweight body also enables buoyant movement, allowing it to float and swim without additional flotation devices.
More unusual capabilities stem directly from its low mass and adaptable structure. The robot has demonstrated the ability to walk across water at low speed, deliver forceful kicks by storing and releasing energy in its flexible elements, and briefly fly when paired with small ducted fans or quadrotor systems. Active control and telescoping reinforcements help maintain balance during these varied movements.
From a defense and homeland security perspective, such adaptability is highly relevant. Robots that can change size and locomotion modes are well suited for urban search and rescue, tunnel inspection, collapsed structures, and hazardous environments where humans face significant risk. The ability to traverse water, debris, and confined spaces without reconfiguration reduces deployment complexity and response time.
While still a research platform, the humanoid demonstrates how combining soft robotics with controlled structural growth can overcome long-standing mobility limits. Rather than forcing robots to operate within rigid constraints, this design shows how adaptability itself can become the primary tool for navigating complex and unpredictable environments.
The research was published here.
