What can we learn from nature? What abilities from the animal world can be used for industrial applications? We have been working on these questions in the Bionic Learning Network for many years. In association with universities, institutes and development companies, we are developing research platforms whose basic technical principles are based on nature. A topic that comes up again and again is the unique movements and functions of the elephant's trunk.
With the Bionic Handling Assistant (2010), the BionicMotionRobot (2017) and the BionicSoftArm (2019), a series of lightweight pneumatic robot arms has emerged over time. They can all effortlessly reproduce the flowing motion sequences of their natural model thanks to their flexible bellows structures. While they were being developed, the designs of the bionic concepts were becoming ever more compact, smaller and quicker to commission.
For the delicate Bionic E-Trunk, our developers, together with the Centre for Mechatronics and Automation Technology in Saarbrücken, Germany, have taken the idea of miniaturisation further and implemented the natural forms of movement for the first time through electric actuation.
The Bionic E-Trunk is made up of two 140-millimetre-long segments with a tapered diameter. Its core comprises a structure made of 3D-printed material and a super-elastic rod for longitudinal stabilisation. Thin wires made of a special metallic material, a so-called shape memory alloy, are arranged around this core, which resembles a spinal column.
The shape memory alloy has 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 react more quickly to how they are actuated.
When creating the concept, the developers chose a design that was similar to that of previous pneumatically actuated trunk projects. Each segment has three wire bundles, each of which consists of two to four individual wires. It can thus be steered in a defined direction depending on the separate activation of the wires The interaction of the artificial muscles in the elements result in the fluid and flexible movements of the Bionic E-Trunk.
Thanks to its low dead 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.
When combined with a micro gripper, the Bionic E-Trunk could be used to handle small objects. In addition, the concept could be used in a dosing process in the life science sector. Flexible tubing could be attached to the side of the structure. This could be used to remove liquids from containers and fill other containers. It would also be conceivable to use it for cleaning confined areas with targeted air flows.
While the pneumatic predecessors were used exclusively to demonstrate how objects can be gripped in a form-fitting way, the Bionic E-Trunk can be used to implement other functions of the elephant’s trunk, such as the intake and delivery of liquids or air.