Dynamic coupling enables impulsive ejection in a hydrogel catapult.

Dynamic coupling in a hydrogel catapult achieves a launch velocity of 16.6 m/s and power density over 8.74×10^4 W/kg, surpassing most natural and engineered systems.

• Why it matters: Miniature robots require high-speed, efficient ejection mechanisms for precise, non-contact operations across various applications, yet existing methods lack the power and speed needed.
• What they did: A bilayer hydrogel catapult was developed utilizing phase-transition-driven deformation that dynamically couples with the projectile and substrate, enabling high kinetic energy transfer across a broad mass range.
• The result: This approach enables rapid, high-power ejections, demonstrated by a biopsy robot that can acquire deep tissue samples in a single shot, advancing the capabilities of soft miniature robotics.