Nature is a model for science. Biomaterial research in Teltow is being inspired by rainforest cacti and climbing plants (vines) to create polymer materials that move and grow independently. One day, these synthetic materials will be used as artificial muscles in so-called soft robots, which are made of soft materials.
The plant shoots grow and search around until they find a hold. This is how they bridge distances. Photo: Hereon/Steffen Niemann
Artificial muscles – climbing plants as a model
The innovations of the future are hidden in thousand-year-old rainforests. The structure and behavior of plants in their natural environment serve as a model for science, especially in the design of sustainable materials. Tropical climbing plants have unique characteristics that can be utilized for very special technologies.
Nicholas Rowe, a researcher from the CNRS in France, explains one of these plants to us. The outer end of the creeper is very sensitive and flexible so that it can actively wind itself around tree branches for support depending on external factors.
In Teltow, scientists from the Helmholtz-Zentrum Hereon are researching artificial materials that are based on these abilities. Andreas Lendlein shows us in experiments in which a material contracts like a corkscrew when heated in water. When it is placed in colder water, it jumps back to its original shape. Materials of this nature could be used in the future as artificial muscles in soft robots, which could be deployed in contact with humans due to their mechanical features. What's more, biomaterial researchers can program the geometry of the muscle movement and the switch temperatures of the material.
The artificial muscles, which are being designed in Teltow using nature as a model, are part of the international GrowBot project. These soft robots, which scientists from all over Europe are researching, could be used in the future, for example, in the fields of health technology, agriculture, or aerospace.
Muscles for Soft Robots
Scientist Anil Bastola studies a sample from a special South American cactus. Artificial muscles for soft robots are produced using this plant as a model. Photo: Hereon/Gesine Born
Novel plastics react to signals such as temperature or magnetic field and move accordingly. Such materials are reprogrammable in that they can be trained in different motion sequences.
By Lars Klaaßen
We live in a society that is increasingly shaped by the need for services, a world in which more and more elderly people rely on assistance in their everyday activities and on the field of medicine. In such a society, artificial assistants—what are known as “soft robots”—will become increasingly important. Soft and sensitive materials enable these assistants to better adapt to the environment and work safely with people. “Role models” include creeping plants that feel and react to their surroundings, as well as South American cacti that can move.
These tendril plants grow and search until they find something onto which they can grab. This allows them to move and cover distances. Photo: Hereon/Steffen Niemann
“To make materials suitable for certain applications, we program them,” says researcher Marc Behl. “We lend them this ability through the interaction of processes on molecular and morphological levels. We are familiar with the effect that a material changes its shape under certain circumstances from observing heat-sensitive shrink films or tubes.” If these items are heated with a hairdryer—a suitcase, for example, can be densely packed. One shortcoming, however, is that this shrinkage cannot yet be reversed.
A few years ago, researchers from the Hereon-Institute of Active Polymers made considerable progress by creating soft actuators with a shape memory, which move back again. The plastic strands or threads that twist or bend are controlled as needed by different signals such as temperature or magnetic fields. Furthermore, such movements can be performed in a fully controlled manner through individual steps, with pauses of desired lengths where the material remains still.
In the future, such actuator materials could be used to build harvesters that swing from tree to tree or care assistants that place people into another bed. To develop artificial robot muscles, the scientists from Teltow now cooperate with experts in soft robotics.