Electrically/Magnetically Dual‐Driven Shape Memory Composites Fabricated by Multi‐Material Magnetic Field‐Assisted 4D Printing

The development of projection‐based stereolithography 3D printing techniques has provided a powerful approach to fabricate millimeter scale functional devices with complex structures. However, the current processes face challenges in frequent switching between multiple materials or processes, resulting in low efficiency and accuracy during the fabrication of bifunctional devices. To address these challenges, chemical deposition is utilized to modify graphene nanoplatelets (GNs) with Fe3O4 magnetic particles and incorporate them into the photosensitive resin, resulting in the development of a novel bifunctional printing material with magnetic and locally conductive properties. Furthermore, the localized conductivity of devices is controlled by an electric‐field‐assisted alignment process of the magnetic GNs (mGNs) during the printing process. Herein, this single‐material projection‐based stereolithography allows for the simultaneous fabrication of magnetic and locally conductive millimeter scale bifunctional devices without switching between multiple materials or processes. A magnetically driven circuit switch and signal coding gear are fabricated as demonstrations. This work significantly improves the efficiency and accuracy of fabricating millimeter scale bifunctional devices, thereby facilitating their application in the fabrication of miniaturized and integrated devices.

Simultaneous Manufacture of Magnetic and Locally Conductive Millimeter Scale Bifunctional Devices via Single‐Material Projection‐Based Stereolithography

Huang,

Yu,

Deng

et al. 2024

Tunable Bio‐Derived Skin‐Like Shape Memory Fibers for Smart Suturing

Liu,

Zhang,

Xiao

et al. 2024

Materials made from bile acids can benefit from the excellent biocompatibility and rigid skeleton of these natural compounds. To address concerns of the biocompatibility of shape‐memory polymers (SMPs) in biomedical applications, a series of polyurethanes (PUs) is developed using bile acid as the hard segment and oligo(ethylene glycol) as the soft segment through a one‐pot polymerization. These polymers can be easily processed into skin‐like fibers, tubes, strips, etc., with tunable mechanical properties, e.g., elongation at break (483%) and high tensile strength (40.9 MPa). Their glass transition temperatures spread across a wide range, enabling them to exhibit dual, triple, and quadruple shape memory effects (SMEs). Due to intermolecular interactions, these PUs display a maximum self‐healing efficiency of 96% in tensile strength for 1.5 h. In vitro cytotoxicity tests, hemolysis evaluations and healing efficiency in vivo all indicate their good biocompatibility and biosafety. These bio‐derived PUs offer an option of shape memory polymers easy to make, with good tissue compatibility for applications as surgical sutures, artificial muscles, and soft materials.

Reversible Emission Color, Brightness, and Shape Changes of AIEgen‐containing Bulk Polymers

Wang,

Si,

et al. 2024

Bulk polymers generally exhibit faster response, higher shape‐deformation speed, and stronger mechanical properties than the hydrogels. However, it still remains a formidable challenge to enable bulk polymers to exhibit reversible changes in shape and fluorescence simultaneously. Herein, for the first time, the temperature‐responsive reversible changes in fluorescence color, brightness, and shape of semi‐crystalline poly(ε‐caprolactone) (PCL) network doped with a D‐A based aggregation‐induced emission luminogen (AIEgen) is realized. The fabricated flower‐like and dragonfly‐shaped actuators show reversible blooming‐closing and wing fanning behaviors, respectively, as well as reversible fluorescence‐changing effects. Notably, the response and shape‐deformation speed as well as mechanical properties of the system is much better than the reported hydrogels. Moreover, a smart switch is developed to demonstrate the potential applications. The stick fabricated by the sample can lift and release an object 1000 times larger than its weight, serving as a color‐changing artificial muscle. This material design strategy may shine light on the design and preparation of other reversible shape‐deformation polymers in combination with stimuli‐responsive luminescence‐changing AIEgens, such as mechanochromic, thermochromic, and photochromic luminogens.