Researchers at TU Delft have developed programmable actuators consisting of both hard and soft materials. This combination enables complex movements. The researchers see great potential in using their development in soft robots, which can safely and efficiently handle both people and fragile objects.
TU Delft researchers describe their findings in an issue of Materials Horizons published early this month. "Robots are usually big and heavy. But you also want to have robots that can handle carefully, for example when dealing with soft tissue in the human body. The field that studies this topic, soft robotics, is now rapidly gaining popularity," Prof Amir Zadpoor, who supervised the research, explains in an article on the TU Delft website.
Soft grip and fast movement
"You are actually looking for something with similar characteristics to the human hand, such as a soft grip, fast yet precise movements, and strength. We are trying to achieve that with our soft programmable materials from the 3D printer."
Soft robots, for which the English term 'soft robotics' is often used, can interact safely and efficiently with both people and delicate objects thanks to their soft touch, without the risk of injury or damage. In the development of such soft robots, the drive system is a challenge: robots' drives usually consist of hard components. These are not suitable for soft robots, which require proper and programmable actuators.
Mechanical instability
The solution lies in flexible metamaterials based on mechanical instability. These materials offer ' unprecedented functions programmed into the material itself', according to TU Delft researchers. which makes the very suitable for soft materials. "However, the adaptability of the mechanical metamaterials proposed so far was very limited," says researcher and lead author Shahram Janbaz.
"We now present several new designs of ultra-programmable mechanical metamaterials where not only the drive force and amplitude but also the drive mode can be chosen and set within a very wide range. We also give some examples of how these soft actuators could be used in robotics, for example as pressure changers, kinematic controllers and pick&place end-effectors."
Distortion
According to Zadpoor, the function is in the material itself. "We therefore needed to study the phenomenon of deformation more closely. It was once considered the epitome of bad design, but in the past few years that property has been brought under control and is being used to co-design mechanical metamaterials with advanced functions. Soft robotics in general and soft actuators in particular can benefit enormously from such design materials. Whether the huge potential of deformation can really be harnessed depends on whether the biggest limitation of the designs presented so far can be overcome: their limited programmability. We could calculate and predict higher degrees of deformation and make the material more amenable to this."
TU Delft's soft actuators (source photo: TU Delft)
The researchers print metamaterials made of multiple materials that are driven by deformation and are highly programmable. Janbaz: "We combined rational design approaches with predictive computational modelling and advanced, 'additive-manufacturing' techniques using multiple materials to print cellular materials with arbitrary distributions of hard and soft materials in the central parts and corners of their unit cells using the 3D printer. We used the geometry and spatial distribution of material properties as key design parameters and used these to develop soft metamaterials that behave like mechanisms whose driving force and amplitude can be adjusted."
Author: Wouter Hoeffnagel
