What Is a Dexterous Hand?

A dexterous hand is a multi-degree-of-freedom robotic end-effector modeled on the structure and function of the human hand: coordinated motion of multiple fingers and joints enables grasping, pinching, and in-hand reorientation of objects. Unlike a two-finger gripper with only open/close states, a dexterous hand adapts to objects and tools of arbitrary shape, making it the key component for humanoid robots moving toward general-purpose manipulation.

Degrees of Freedom: Underactuated vs Fully Actuated

The human hand has roughly 20+ degrees of freedom; dexterous-hand design trades off human-likeness against engineering reliability:

• Underactuated (about 6-12 actively driven DOF): fewer motors than joints, with multiple joints coupled to one drive and mechanical compliance conforming to the object. Lower cost, higher reliability, covers most grasping tasks;
• Fully actuated (20+ DOF): every joint independently controlled, enabling in-hand manipulation and other demanding skills — at the price of complexity, cost, and maintenance, so mostly found on research platforms.

Actuation Approaches

• Coreless-motor direct/geared drive: exploits the power density of coreless motors to fit actuators inside fingers or the palm — fast response, compact structure;
• Tendon drive: motors sit in the forearm and pull fingers via tendons (like human anatomy), keeping the hand light, but friction and cable elasticity introduce control error;
• Linkage drive: rigid linkages transmit motion with good precision and stiffness, at some cost in DOF layout flexibility.

Role in Humanoid Robotics

The dexterous hand defines what work a humanoid can actually do. In embodied AI research, dexterous manipulation data is mostly collected through teleoperation — data gloves, exoskeletons, VR — to train imitation-learning policies. More hand DOF means a larger learnable task space, but also harder data collection and control, which is why most deployments today still start from grippers or underactuated hands.