A new three-fingered hand peels fruit, flips cards and lifts coins from flat surfaces
The three-fingered hand peels an orange using the stiff nails to grasp and pierce the skin of the fruit. Nails can also cause the top of a thin lid to burst.
DH Kang and others/arXiv, 2026
Robotic hands are doing their nails.
Researchers have designed a new three-fingered robotic hand whose digits are accompanied by a stiff nail on a soft material. The design gives the robotic hand the ability to peel fruit, open containers with lids and pick up flat objectsthe team published on arXiv.org on February 5. The results offer insight into the types of real-world tasks and industrial material handling tasks the robot could perform.
The tips of most conventional robotic hands feature a soft pad over a rigid structure, giving the fingertip a square shape. The new robot’s fingertips feature a soft material wrapped around the “skeleton” of the finger, with a rigid structure on top, giving the tip an oval shape, closer to that of our fingers. “A square shape only accommodates forces coming directly from there, but our design can also respond flexibly to twisting or lateral forces,” says mechanical engineer Dong Ho Kang of the University of Texas at Austin.
The soft fingertips with a square design conform to and grip objects, but that same softness makes them less precise. In humans, stiff nails on soft fingertips correct this problem by stiffening the fingertips and concentrating pressure.
Taking inspiration from our own fingernails, researchers tested robotic hands with three linked motorized fingers – the index, middle and thumb – with and without nails. The fingers grasped flat objects, domed outward and curved inward, while the objects were pulled upward. Fingertips with nails demonstrated stronger grip strength, meaning they had a tighter grip, Kang says. Nails were an advantage for gripping curved objects. Without them, soft fingers were easily deformed and had a less stable grip on objects.
Fingertips with nails also excelled at extracting a single sheet from a stack of papers, opening the lid of a sealed container, picking up thin objects like coins and cards from a surface, and turning over cards. Although they successfully opened the lid on some attempts, the soft fingertips without nails failed in all other tasks and were unable to make contact with the edges of the objects. Kang says the next step will be to extend this work to a complete robotic hand.
