Soft gripper based on DEAs and electroadhesion

How does one make a robotic gripper delicate enough to grab a strawberry, but strong enough to hold a can of soup?

A collaboration between EPFL-LMTS (Prof. Shea) and EPFL-LIS (Prof Floreano). Lead scientist for ongoing work: Dr V. Cacucciolo 

Soft gripper based on DEA and electroadhesion

Our first version of this work was published in Advanced Materials (2015).

We developed a novel method to create soft and compliant grippers based on combining electrostatic actuation (gentle bending driven by DEAs) with an optimized electroadhesion force, which enables us to manipulate deformable, fragile objects of any shape with a single control signal.
To illustrate the impressive abilities of our device, we developed a compliant gripper, weighing only 1.5 g. The two-fingered gripper easily and safely picks up a series of  objects that would be very challenging for conventional robotic manipulators. in the movie below, we pick up a raw egg, a piece of flat paper, and a 73 g water balloon. The movies above show handling of even heavier objects. Our gripper opens and closes in about 100 ms, thanks to the use of silicone elastomers and silicone-based electrodes.

 

The plot below shows the importance of grasping pose, in particular grasping angle, for high gripping force. details here.

 

Operating principle

The actuator consists of two interdigitated electrodes sandwiching an elastomer membrane. Applying a voltage forms electric fields at the inside the structure and the outside. The E-field inside the elastomer generates the Maxwell-stress compressing the membrane, leading to actuation (bending of the gripper). The E-field outside the elastomer leads to an electro-adhesion force on objects into which the field penetrates.

Structure of DEA

This gripper produces both the electro-adhesion (several Newtons of shear force per cm2) and a gentle gripping force.

References:

Shintake J, Rosset S, Schubert B, Floreano D, Shea H. Versatile Soft Grippers with Intrinsic Electroadhesion Based on Multifunctional Polymer Actuators. Advanced Materials. 2016;28(2):231–238

https://onlinelibrary.wiley.com/doi/full/10.1002/adma.201504264

 

Shintake J, Cacucciolo V, Floreano D, Shea H. Soft Robotic Grippers. Advanced Materials. 2018 Jul 1;30(29):1707035 (review paper)

https://onlinelibrary.wiley.com/doi/full/10.1002/adma.201707035

 

Cacucciolo V, Shintake J, Shea H. Delicate yet strong: Characterizing the electro-adhesion lifting force with a soft gripper. In: 2019 2nd IEEE International Conference on Soft Robotics (RoboSoft)

https://ieeexplore.ieee.org/document/8722706