cs.ROOct 21, 2026

PHD-Hand: A Printable Humanoid Dexterous Hand with Linkage-Driven 3-DOA Digits

Authors: Neel Adwani, Muhaiminul Islam Akash, Saffia Ouali, Ethan Liu, Cong Wang

Organizations: Electrical and Computer Engineering, New Jersey Institute of Technology (NJIT) · Union County Magnet High School, USA

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Abstract

Currently, dexterous humanoid robot hands are widely considered the final hardware bottleneck that hampers generalist robots from physically assisting people at home and work. As conventional tendon-driven designs suffer from high cost, demanding maintenance, poor reliability, and short durability, alternative linkage-driven designs have increasingly gained attention. Despite their potential to avoid the weaknesses of tendon-driven hands, integrating multiple degrees of actuation (DOA) in a single digit with linkage drivetrains is a challenge for design and fabrication. Only a few studies have managed to present functional humanoid hands that are completely linkage-driven and have at least three DOAs per digit without compromising actuator placement and other design preferences. Our work introduces a new linkage-driven hand featuring a unique flexure hinge. Together with elastic drive rods made of spring steel, the linkage drivetrains are significantly simplified. Unlike other linkage-driven designs of similar dexterity, our design does not require many miniature moving parts. As a result, the hand can be fabricated easily with a budget 3D printer. This not only significantly lowers the barrier to entry for using and developing dexterous humanoid robot hand functions, but also allows the hands to be sized much closer to regular human hands. The design offers desirable kinematic advantages as well. A prototype is evaluated for grasping and object manipulation. In addition, this paper presents our latest findings on kinematics and control of the hand.

Figures & tables

Fig. 1: A representative existing design of linkage-driven 3-DOA digit [ 13 ] , a - schematic, b - parts and components
DesignThis work[ 13 ] [ 14 ] (replicated) [ 15 ] (improved)[ 16 ][ 17 ]L20 by Linkerbot (commercial product)
Release year20262021, 2025, 202520222024after 2023
Digits1 thumb + 4 fingers1 thumb + 4 fingers1 thumb + 2 fingersSingle digit only1 thumb + 4 fingers
DOAs / digit33 [ 13 ] [ 14 ] 3 each finger and 4 on the thumb [ 15 ]3 each finger and 4 on the thumb33 each finger, 4 on the thumb
Major parts / digit (including digit body and drivetrain but not actuators and sensors)13 if the phalanges and digit joints are made in one piece; 18 if made separate parts27+27+(No physical demonstration yet)(unknown)
Fabrication requirementDIY with a budget 3D printerindustrialindustrial(No physical demonstration yet)industrial
Kinematics of root joint and upper two jointsCompletely decoupledPartially coupledPartially coupledPartially coupled(unknown)
TABLE I: Comparison between the proposed design and its peers
Fig. 2: The proposed design of a digit
Fig. 3: Prototype - (a) whole hand, (b) modular digit, (c) 3D printing of the 2-DOF flexure hinge
Fig. 4: Notations for inverse kinematics of the root joint
Fig. 5: Error of an affine approximation of the root joint’s kinematics. qfq_{f} and qlq_{l} are as defined in Fig. 4
Fig. 6: A GUI generated by AI
Fig. 7: AI-generated motion trajectories - (a) draft, (b) revised
Fig. 8: Validation of grasping ability according to the GRASP taxonomy [ 26 ]
Fig. 9: Thumb opposition
Fig. 10: Object manipulation
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