Manufacturing, programming and actuation of graded printed magnetoresponsive smart materials

• Applicants: Professor Dr.-Ing. Stefan Junk; Professor Dr.-Ing. Thomas Seifert
• Subject Area: Synthesis and Properties of Functional Materials ; Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 558319173

Because of their ability to deform and change size, soft robots are relevant to many industrial and medical applications. For example, soft robots can interact directly with humans. Soft grippers can handle delicate objects and adapt to different shapes. By using soft smart materials that can respond to external stimuli such as heat, light, and electric or magnetic fields, soft robots are able to perform "untethered" motions, i.e., without being connected to an external power supply. This is particularly relevant when soft robots are triggered by remote control. Soft robots made of magnetically responsive elastomers (MRE) can be programmed by applying magnetic fields above the coercive field strength, giving them a special magnetic profile so that they can subsequently be activated to a specified target geometry in weaker magnetic fields. The 3D printing of smart materials, often referred to as 4D printing (three-dimensional geometry plus temporal modification), makes it possible to use complex bionic structures for soft robots and to exploit the geometric freedom of 3D printing for targeted interaction between geometry and external stimulus. MRE can be fabricated in 4D printing as a composite of a highly elastic matrix and magnetizable particles. The local magnetic and mechanical properties of the printed structure can be optimized by locally varying degrees of filling and thus graded MRE. The current state of scientific research shows that the reversibility of the behavior of MRE is influenced by different mechanisms. Which mechanisms are relevant for the programming and actuation of particle-filled thermoplastic elastomers processed by pellet 4D printing and how these mechanisms are influenced by the degree of filling and grading (multi-material) is not yet known. Therefore, the main objective of this project is to investigate and understand these mechanisms in order to define printing and programming strategies in multi-material pellet 4D printing of MRE that allow reproducible and reversible actuation. In the project, thermoplastic elastomers (TPE) with good mechanical properties are used as matrix material. They are available in different hardnesses and are easy to process, e.g. thermoplastic polyurethane. The TPE is filled with hard magnetic particles, whereby different magnetic properties are realized by different degrees of filling. Finally, the findings on reversibility and reproducibility will be applied to the design of graded printed components for soft robots.

• DFG Programme: Research Grants