Bionic E-Trunk

Movement concept according to natural model

What can we learn from nature? What skills from the animal world can be used for industrial applications? We have been dealing with these questions in the Bionic Learning Network for years. In association with universities, institutes and development companies, we are developing research platforms whose basic technical principles are based on nature. A recurring theme here is the unique movements and functions of the elephant's trunk.

Pneumatic predecessors from the Bionic Learning Network

With the Bionic Handling Assistant (2010), the BionicMotionRobot (2017) and the BionicSoftArm (2019), a series of lightweight pneumatic robot arms has emerged over time. With their flexible bellows structures, they can all effortlessly implement the flowing motion sequences of the natural model. As they evolved, bionic concepts became more compact, smaller in size and quicker to put into operation.

Electric driven miniature

For the filigree Bionic E-Trunk, our developers, in cooperation with the Center for Mechatronics and Automation Technology in Saarbrücken, have taken the idea of miniaturization further and for the first time implemented the natural forms of motion electrically driven.

The Bionic E-Trunk is made up of two 140 millimeter long segments with a tapered diameter. In its center runs a structure of 3D-printed material and a superelastic rod for longitudinal stabilization. Thin wires made of a special metallic material, a so-called shape memory alloy, are arranged around this center, which resembles a spinal column.

Infographic BionicE Trunk

Artificial muscles with shape memory alloy

The shape memory alloy exists in two different structures depending on the temperature: if it is heated - for example with the help of electricity - the wires shorten. When they cool down, they "remember" their former shape and return to their original position. This allows the Bionic E-Trunk to bend individually and in a controlled manner in any spatial direction. The thinner the wires the faster they heat up, cool down again and thus respond more directly to their control.

Controlled, filigree movements

In building the concept, the developers chose a similar arrangement to that used in the pneumatically driven trunk projects of the past. Three wire bundles, each consisting of two or four individual wires, are installed per segment. It can thus be steered in a defined direction depending on the separate activation of the wires. In interaction with each other, these artificial muscles in the elements provide the fluid and flexible movements of the Bionic E-Trunk.

Thanks to its low intrinsic weight of only twelve grams, the trunk can be moved easily with the actuators made of shape memory alloys. Compared to other drive principles, they have the highest force-to-weight ratio.

Bionic E-Trunk: movement concept based on natural models

Relaxed starting position: both segments in their original position (left)
Maximum curvature: shortening of the wires by electrical heating (right)

Conceivable applications and potential uses

In combination with a micro gripper, the Bionic E-Trunk could be used to handle small objects. In addition, the concept would enable a dispensing process in the life science sector. For this purpose, a flexible hose could be attached to the side of the structure. This could be used to remove liquids from vessels and transfer them to other containers. This would also make it possible to deliver targeted air streams for cleaning constricted areas.

While the pneumatic predecessors were used exclusively to demonstrate the positive gripping of objects, the Bionic E-Trunk can be used to implement other functions of the elephant's trunk: the intake and delivery of liquids or air.