Cephalopod-Inspired Magnetic Shape-Morphing System for Dynamically Reconfigurable 3D Displays and Soft Robotics

Shape-programmable mechanisms, emulating the biological morphing abilities of living organisms, have been a profound source of inspiration for engineers to utilize in diverse applications that require complex 3D structural transformation. Particularly, cephalopods (e.g., cuttlefish, squid, octopus) excel in the reversible transformation of their skin texture using muscular hydrostat, known as papillae, enabling effective camouflage and adaptation to surrounding habitats. Inspired by these features, several technologies to achieve 3D complex configurations from a 2D surface in programmable and reversible manners are on the verge of advancing multiple fields including 3D electronics, robotics, and biomedical applications.
To realize such possibilities, various research in structural (e.g., buckling, kirigami, origami) and actuation (e.g., thermal, pneumatic, electromagnetic) approaches for metamaterials and stimuli-responsive materials (e.g., liquid crystal elastomer, shape memory polymer) have been widely explored to establish systems with 2D-to-3D transformation. However, it is still challenging to consecutively implement a broad range of reversible 3D configurations in a single system. Among the prospective candidates, magnetic soft materials that consist of magnetic particles embedded within a polymeric matrix are particularly appealing. Their unique properties are wireless control over programmable shape changes and locomotion allowing far-reaching implications regardless of environmental obstacles. In addition, they enable rapid and versatile shape reconfigurations, facilitating the transition between various 3D structures in response to the magnetic field. Despite these advantages, a significant limitation of magnetic soft materials lies in their dependence on the continuous magnetic field for maintaining the deformed shape, resulting in power inefficiency. Furthermore, the intrinsic softness of such materials entails difficulties in achieving 3D configurations with both high geometrical complexity and sufficient mechanical stability, which hampers their reliable applicability in diverse electronic devices.
Here, we address these challenges with inspiration from the skin texturing behavior of cephalopods using the magnetic shape-morphing platform (mSMP) for constructing a programmable 3D magnetic shape-morphing system that reversibly modulates its morphology and stiffness. The mSMP can realize intricate 3D configurations through the combination of thermal and magnetic stimuli under complex preprogrammed magnetization profiles. This composite consists of low melting point alloy (LMPA) (specifically, Field’s metal; FM) droplets with ferromagnetic particles (i.e., Neodymium iron boron; NdFeB) within a polymer matrix. Owing to stiffness modulation by phase transition of FM, the mSMP can be morphed into 3D structures (i.e., soft mode) and firmly retain its deformed shapes (i.e., rigid mode) with cooling to provide reliable device operation. Furthermore, it enables agile reversible shape transformations and possesses reprogrammable magnetization capabilities, allowing multi-morphological reconfiguration. It mitigates the power consumption resulting from the continuous application of external stimuli. Utilizing these advantageous features, we have demonstrated a magnetic robot (e.g., light-responsive FlowerBot) and a refreshable dynamic 3D surface for visio-tactile displays (e.g., cryptographic display, 3D programmable textual display, and dynamic braille display systems), highlighting the potential of a 3D magnetic shape-morphing system for real-world applications. This breakthrough is poised to revolutionize various fields such as 3D electronics and soft robotics, offering innovative strategies for the advancement of 3D displays and soft robots capable of shape-morphing and seamlessly integrating into their environments.