Researchers at the University of Stuttgart and the Max Planck Institute for Solid State Research have developed tiny rolls that can be unrolled and rolled up in a controlled manner using a magnet. The model for this was the proboscis of butterflies. These smart materials enable the development of more efficient drive technologies for micro- and soft robotics, a field of research of great economic importance. The results have been published in the journal Advanced Materials.
New robotic systems are increasingly making headlines: Microrobots are extremely small robots with potential applications in fields such as medicine and industry. At the same time, the field of soft robotics – which relies on flexible, adaptable materials – is advancing to make robots more adaptable and safer. Just as in (macroscopic) robotics, actuators must also control movements or grippers in micro- and soft robotics. However, because the overall systems in microrobotics are much smaller and, in soft robotics, must be elastically formable, this creates entirely new requirements for the components of such a system. These requirements can often only be met by using new materials. This is where the team led by Dr. Zaklina Burghard, group leader at the Institute for Materials Science at the University of Stuttgart, stepped in.
"Micro- and soft robotics require actuators that enable robotic systems to grasp, move, and interact with their environment," says Burghard. "We did not simply develop another actuator. We created a manufacturing platform that transforms ultrathin functional films into programmable three-dimensional ceramic microscrolls within seconds. These microscrolls serve as compact actuation elements for future robotic systems." The technology platform is the latest outcome of Burghard's long-standing research into bio-inspired ceramic material systems.
Inspired by the butterfly proboscis
The butterfly did not inspire the biological function of the actuator, but the elegant rolling and unrolling motion of its proboscis. This characteristic movement became the starting point for developing the new ceramic microscrolls. Researchers fabricated ultrathin vanadium pentoxide films containing magnetic iron oxide nanoparticles and transformed them into three-dimensional microscrolls using a simple mechanical process.
To fabricate the microscrolls, the ultrathin ceramic films are gently peeled from their substrate with a razor blade. Acting much like a miniature woodworking plane, the blade continuously bends the released film, causing it to roll into a tightly wound microscroll within seconds. Bringing a magnet close to the microscroll causes it to rapidly unroll; removing the magnetic field allows it to roll back again.
Unlike conventional ceramics, these ultrathin films are not brittle but flexible. Their unusual mechanical behavior arises from a bio-inspired hierarchical nano- and microstructure, which enables elastic deformation while preserving the structural integrity of the ceramic material.
Tiny ceramic microscrolls lift more than 30 times their own weight
The researchers have produced rolls that are a few micrometers wide and, when coiled, have a diameter of only a few hundred micrometers. When rolled out, they are up to 25 mm long. In experiments, the rollers have proven to be very durable: Even after 5,000 cycles, they still work perfectly. The ceramic micro-rollers are capable of moving more than 30 times their own weight. ""The microscrolls can also be arranged into programmable arrays," says Burghard. "This allows multiple actuators to operate simultaneously and perform coordinated tasks such as lifting, transporting, or manipulating microscopic objects."
Vanadium pentoxide was selected as the model material because it has been at the center of Burghard's research for many years and provided the ideal foundation for developing the new manufacturing platform.
„For me, the actuator is only the beginning," says Burghard. "The real innovation is the scrolling platform itself. It can be transferred to many different organic and inorganic thin-film materials, opening the door to entirely new programmable microsystems." Beyond micro- and soft robotics, the platform could enable future electronic components, sensors, energy-storage devices, and other multifunctional microsystems tailored to specific applications.
Nature as a blueprint for future materials
The development of the magnetic ceramic microscrolls began within a DFG-funded research project led by Burghard. As part of this project, Semi Kim carried out the first experimental studies during her master's thesis in 2023, laying the foundation for the present study. Building on these initial results, the research team further expanded and refined the concept.
The research is carried out in the Department of Bioinspired Materials at the Institute for Materials Science. "In our department, we combine nature as a source of inspiration with modern materials science. Students learn how principles from physics, chemistry, computational modelling, and bio-inspired materials design are integrated to develop the next generation of functional materials and programmable microsystems. This unique interdisciplinary approach is reflected directly in our research," says Burghard. "Our work brings together bio-inspired concepts, ceramic nanomaterials, magnetic functionality, mechanics, and advanced manufacturing into a single platform for the programmable microsystems of the future."
About the publication:
Semi Kim, Shravan R. Kousik, Petia Atanasova, Eberhard Goering, Joachim Bill, Zaklina Burghard: Mechanically Assisted Magnetic Actuation in Ceramic-Based Microscrolls for Fast and Durable Soft Robotic Systems, Advanced Materials, http://doi.org/10.1002/adma.74544
