Recent advancements in lead halide perovskites opened up an avenue for vast optoelectronic applications. However, lead toxicity and the complicated synthesis process posed major obstacles to their further practical applications. To address these issues, a facile and robust mechanochemical synthesis of cesium manganese halide (Cs₃MnX₅, X = halide element) was developed via a highly efficient solvent-free ball milling strategy. This green approach exempted the utilization of any harmful organic solvents, thereby enabling the fast and cost-effective production of lead-free Cs₃MnX₅ with excellent optical properties. Cs₃MnX₅ perovskites with mixed halide compositions could also be readily fabricated through this eco-friendly approach at room temperature without any post-purification. Furthermore, the robustness of the ball milling strategy was proved by fabricating zinc-doped Cs₃MnX₅ perovskites with enhanced thermal stability and ambient stability. These features demonstrated that ball milling was highly efficacious for producing high-quality non-toxic halide perovskites, which could be used in light-emitting diodes.

Liquid metal (LM) and liquid metal alloys (LMs) possess unique physicochemical features, which have become emerging and functionalized materials that are attractive applicants in various fields. Herein, uniform LM nanodroplets armored by carbon dots (LMD@CDs) were prepared and exhibited high colloidal stability in various solvents, as well as water. After optimization, LMD@CDs can be applied as functional additives for the 3D/4D printing of hydrogel and cross-linked resin through digital light processing (DLP). The light absorption of LMD@CDs not only improved the printing accuracy, but also led to the cross-linking density differential during the post-curing process. Base on the cross-linking density differential of soft hydrogel and photothermal performance of the LM, the 3D printed objects can exhibit stimulus responses to both water and laser irradiation. Additionally, the CDs shell and LM core of LMD@CDs provide the printed objects interesting photoluminescence and electric conductivity capabilities, respectively. We deduce this versatile 3D/4D printing system would provide a new platform for the preparation of multi-functional and stimuli-responsive advance materials.