Sanctuary Phoenix Hydraulic Hand

The Sanctuary Phoenix Hydraulic Hand is a proprietary robotic hand developed by Sanctuary AI as the end-effector for its Phoenix humanoid robot. The hand has 21 active degrees of freedom, including finger abduction, enabling in-hand manipulation — a capability rarely found in commercial robotic hands.

A core element of the design is a set of miniaturized hydraulic valves developed by Sanctuary AI. According to the manufacturer, hydraulic actuation provides an order of magnitude higher power density than cable-driven and electromechanical systems, with advantages in speed, strength, controllability, cycle life, impact resistance, and thermal management. Sanctuary AI has reported testing its hydraulic valve actuators for over 2 billion cycles without leakage or degradation.

The hand is designed in a modular format, intended for integration with both humanoid and non-humanoid general-purpose robots. Sanctuary AI uses the hand as a platform for training dexterous manipulation policies via reinforcement learning in simulation, with zero-shot transfer to real-world execution — including in-hand cube reorientation under a 500 g out-of-distribution load.