OpenBionics | NTUA – Affordable, Modular, Light-Weight, Underactuated Robot Hands

Year: 2014

Groups: OpenBionics, NTUA

Hand Type: Robot Hand

Weight: < 200 gr

Cost: < 100$

Maximum Fingertip Force: 18 N

Time of Closure (from fully closed to fully open): < 1 s

Total fingers: 2-4 depending on the version

Compliant fingers: yes

Type of motors: Servo Motor

Underactuation: yes

Tendons: yes

Anthropomorphism: no

Sensory System: no

Number of motors: 1

Number of DoF: 4-10 (depends on the version)

Number of fingers: 4-5 (depends on the version)

CAD Files: All files required for the replication of the robot hands can be found in the OpenBionics GitHub Repository.


The OpenBionics has developed and freely distributed a series of affordable (<100$), modular, light-weight (<200 gr), underactuated robot hands based on flexure joint. The design is based on a simple but yet effective idea: to use agonist and antagonist forces to implement flexion and extension of robot fingers, following a bioinspired approach where steady elastomer materials (silicone sheets) implement the human extensor tendons counterpart, while cables driven through low-friction tubes, implement the human flexor tendons analogous. A disk-shaped differential mechanism has been developed, in order to connect all the independent finger cables with the actuator (servo motor). The differential mechanism, allows for independent finger flexions in case that one or multiple fingers have stopped moving, due to workspace constraints, or in case that they are already in contact with the object surface. More details can be found in the OpenBionics initiative website.

How to cite:

Agisilaos G. Zisimatos, Minas V. Liarokapis, Christoforos I. Mavrogiannis and Kostas J. Kyriakopoulos, “Open-Source, Affordable, Modular, Light-Weight, Underactuated Robot Hands”, IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Chicago (USA), 2014.