Investment micro-casting 3D-printed multi-metamaterial for programmable multimodal biomimetic electronics

The bigger pictureIntroducing metamaterials into biometric electronics has been reported to enrich and innovate physical functionalities. Such performances rely heavily on the sophisticated combination of micro-units and higher-performing materials. However, forming compatibility among advanced materials and processing properties hinders the spatial shaping of multiple structures, composite selection, and function integration. To address this issue, we propose an ancient lost-wax-inspired approach, the Boolean-logic-guided investment micro-casting 3D stereolithography strategy (BμSL), striking a trade-off in multi-metamaterial construction and alleviating the difficulty in function-oriented forming. The programmed piezoelectric multimodal neurological devices imitate delicate human manipulation with real-time grabbing feedback and stiffness self-recognition. It fosters the bridging of bio-like energy conversion with embodied intelligence, making no extra process limitation for biometric function integration.Highlights•Investment micro-casting 3D printing is proposed for programmable electronics•Hydrophobic hollowed molds are formed via 3D soluble resin-based templates•Over 20 types of challenging-to-form metamaterials are formed without destruction•Biomimetic flexible piezoelectric devices are achieved for multimodal self-sensingSummaryBiometric electronics have gained considerable attention in self-sensing, three-dimensional (3D) designs, mechanical drive, and multi-function integration. By leveraging these anisotropic capabilities into devices, metamaterial offers a promising pathway to exciting performance-oriented units. However, such distinctive mismatches in forming processes and inherent material properties are severely restricted in achieving cross-scaled microstructures, causing compatibility issues among well-defined bio-functions and fabrication. Herein, we propose an investment micro-casting 3D printing strategy for custom-molding multi-metamaterials without process barriers. This approach handles the bottlenecks of the hierarchical template replacement in ultra-hydrophobicity microchannels for the free assembly of more than 20 types of challenging-to-form materials. A series of piezoelectric metamaterials are programmed with broadband ranges, imitating nerve distribution that has human-feel touch, bending, and recognition. Our work benefits the stiffness self-perception in dynamic grabbing manipulation, broadening the application of multimodal electronics in bio-embodied robots.Graphical abstract