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Soft Robotic Hand

About

The Sorotoki toolkit provides a soft robotic hand with a higher level of complexity compared to the previous soft robots (see above). This design is inspired by the work of Laake et al. 1 and Fras et al. 2. The soft robotic hand consists of five independently controlled soft fingers that can be actuated using pneumatics or fluidics. Each finger is fabricated using a SLS technique with Elastic 80A, while the base is fabricated using FDM with PLA. The dimensions and scale of the soft robotic hand are similar to those of a human hand, with approximate dimensions of 190 \(\times\) 100 \(\times\) 40 mm. All fingers have a length of 90 mm except for the thumb, which is slightly shorter at 80 mm. The soft robotic hand has five independent inputs that accept pressures of \(-10 \le u \le 60\) kPa.

Fabrication details

The soft hand is fully printable. Below, we provided a list of the printer materials.

  • 4\(\times\): Soft Finger - Elastic 80A - Formlabs (recommended)
  • 1\(\times\): Soft Thumb - Elastic 80A - Formlabs (recommended)
  • 1\(\times\): Finger Connector - Rigid 10k - Formlabs (recommended)
  • 1\(\times\): Rigid Palm - Prusament PLA White - Prusa (optional)
  • 1\(\times\): Rigid Base - Prusament PLA White - Prusa (optional)
Printing of Elastic 80A

When printing Elastic 80A, the recommended supports for the material are very thick -- thus difficult to remove. We recommend generating the supports using Rigid 10K, then change the material to Elastic 80A. Support can then be easily removed manually (no pliers required).

Cleaning and closing of Soft Actuators

A crucial step is cleaning of the elastic resin parts. If residual resin is not properly removed/cleaned, it will greatly affect the quality and performance of the soft actuator. We recommend following the cleaning procedures proposed in Proper et al. 1, see Git documentation. The paper draft can be found here: Paper.pdf. In their approach, a perastaltic pump is used to pump cleaning fluid through the soft actuator prior to curing. To allow fluid to flow, both sides of the soft actuator are open! They must be closed using 3 mm plug printed from the same material! The plug can be glued in place using uncured resin, and then placed in an UV chamber for a short duration.

Connecting Soft Actuator to Rigid Connector

Similar to closing of the soft actuators, uncured resin can be used to make a robust connection to the rigid pressure connector. This greatly improves air-tightness of the complete system.

Downloadable content

Complete Soft Robot Hand - uncompressed 14.3 MB (zip)

Rigid Palm (STL) Rigid Base (STL) Finger Connector (STL)

Soft Finger(s) (STL) Soft Thumb (STL)

3D Visualization

Bibliography

  1. Lucas C. van Laake, Jelle de Vries, Sevda Malek Kani, and Johannes T. B. Overvelde. A fluidic relaxation oscillator for reprogrammable sequential actuation in soft robots. Matter, 5(9):2898–2917, 2022. doi:10.1016/j.matt.2022.06.002. ↩↩

  2. Jan Fras and Kaspar Althoefer. Soft Biomimetic Prosthetic Hand: Design, Manufacturing and Preliminary Examination. In 2018 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), pages 1–6. IEEE, 2018. doi:10.1109/IROS.2018.8593666. ↩