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Abstract Traditional piezoelectric materials, such as lead zirconate titanate (PZT), are widely used due to their superior ability to convert mechanical energy into electrical energy. However, these lead-based ceramics are highly toxic and environmentally hazardous. This report explores Rochelle salt as an eco-friendly alternative, despite its brittleness and lower piezoelectric properties compared to PZT. The study investigates methods to enhance the energy capture of Rochelle salt crystals(RS) by varying crystal volume, impact frequency, and force, as well as by incorporating the 3D-printed biomimetic structure inspired by the pomelo fruit peel, which is naturally optimized for absorbing out-of-plane crushing forces. Experimental crystals grown within this structure were compared with those grown without it, focusing on energy capture and durability. Additionally, units with a 64:36 crystal-to-resin ratio were designed to assess the impact of crystal volume on voltage output. The experiments involved varying impact frequencies (120 rpm and 250 rpm) and compression distances (0.034 and 0.068 inches) using a digital oscilloscope and a custom crank slider mechanism. The results indicate that reducing crystal thickness and increasing rpms enhance voltage capture, suggesting that biomimetic structures can significantly improve the mechanical and electrical performance of piezoelectric materials. 

Abstract This study explores a novel multi-material 3D printing technique for fabricating bioinspired hydrogel-Rochelle salt composites, focusing on optimizing concentration, cooling, and coating parameters to enhance material performance. The hydrogel-Rochelle salt composite is a promising material due to its lightweight, mechanical robustness, and piezoelectric properties, making it suitable for applications in sensors, medical devices, and structural materials. A series of concentration tests was conducted to determine the optimal Rochelle salt concentration for achieving efficient curing depth and exposure time. The results identified 50wt% hydrogel/50wt% Rochelle salt as the optimal concentration, providing a balanced curing profile essential for ensuring reliable layer adhesion and structural consistency. To enable controlled crystallization, a cooling process was introduced, with a cooling time of 15 minutes found to be sufficient for complete crystallization to a depth of 500 microns. Thermal imaging and microscopy confirmed the stability of the crystalline structure within the hydrogel matrix, ensuring the material’s functional integrity. Additionally, applying a coating to the printed structure significantly improved surface uniformity and durability, embedding the crystalline elements more effectively within the hydrogel matrix and enhancing the composite’s overall structural integrity. This coating process allowed the composite to withstand repeated printing cycles, facilitating the construction of layered, multi-material structures with improved mechanical and functional properties. The results highlight the importance of fine-tuning concentration, cooling time, and coating techniques to achieve optimal performance in multi-material 3D printing. By addressing these factors, the study demonstrates a reliable approach to producing hydrogel-Rochelle salt composites with high structural quality and piezoelectric functionality. This method not only enhances the material’s durability and adhesion between layers but also opens new possibilities for creating customized, multifunctional materials. The developed process holds significant promise for applications that require precise control over material properties, such as wearable electronics, medical implants, and lightweight structural components. In conclusion, this research provides valuable insights into the fabrication of hydrogel-Rochelle salt composites through advanced 3D printing techniques. The findings offer a foundation for future exploration in multi-material printing and composite fabrication, paving the way for the development of versatile materials with tailored properties for diverse applications. 

Abstract Bionic multifunctional structural materials that are lightweight, strong, and perceptible have shown great promise in sports, medicine, and aerospace applications. However, smart monitoring devices with integrated mechanical protection and piezoelectric induction are limited. Herein, we report a strategy to grow the recyclable and healable piezoelectric Rochelle salt crystals in 3D-printed cuttlebone-inspired structures to form a new composite for reinforcement smart monitoring devices. In addition to its remarkable mechanical and piezoelectric performance, the growth mechanisms, the recyclability, the sensitivity, and repairability of the 3D-printed Rochelle salt cuttlebone composite were studied. Furthermore, the versatility of composite has been explored and applied as smart sensor armor for football players and fall alarm knee pads, focusing on incorporated mechanical reinforcement and electrical self-sensing capabilities with data collection of the magnitude and distribution of impact forces, which offers new ideas for the design of next-generation smart monitoring electronics in sports, military, aerospace, and biomedical engineering. 

Abstract Natural organisms have evolved a series of versatile functional biomaterials and structures to cope with survival crises in their living environment, exhibiting outstanding properties such as superhydrophobicity, anisotropy, and mechanical reinforcement, which have provided abundant inspiration for the design and fabrication of next‐generation multi‐functional devices. However, the lack of available materials and limitations of traditional manufacturing methods for complex multiscale structures have hindered the progress in bio‐inspired manufacturing of functional structures. As a revolutionary emerging manufacturing technology, additive manufacturing (i.e., 3D printing) offers high design flexibility and manufacturing freedom, providing the potential for the fabrication of intricate, multiscale, hierarchical, and multi‐material structures. Herein, a comprehensive review of current 3D printing of surface/interface structures, covering the applied materials, designs, and functional applications is provided. Several bio‐inspired surface structures that have been created using 3D printing technology are highlighted and categorized based on their specific properties and applications, some properties can be applied to multiple applications. The optimized designs of these 3D‐printed bio‐inspired surfaces offer a promising prospect of low‐cost, high efficiency, and excellent performance. Finally, challenges and opportunities in field of fabricating functional surface/interface with more versatile functional material, refined structural design, and better cost‐effective are discussed. 

Collecting fog water is crucial for dry areas since natural moisture and fog are significant sources of freshwater. Sustainable and energy-efficient water collection systems can take a page out of the cactus’s playbook by mimicking its native fog gathering process. Inspired by the unique geometric structure of the cactus spine, we fabricated a bioinspired artificial fog collector consisting of cactus spines featuring barbs of different sizes and angles on the surfaces for water collection and a series of microcavities within microchannels inspired by Nepenthes Alata on the bottom to facilitate water flowing to the reservoir. However, replicating the actual shape of the cactus spine using conventional manufacturing techniques is challenging, and research in this area has faced a limitation in enhancing water-collecting efficiency. Here, we turned to 3D printing technology (vat photopolymerization) to create bio-mimetic fog collectors with a variety of geometric shapes that would allow for the most effective conveyance and gathering of water. Various barb sizes, angles between each barb in a single array, spine and barb arrangements, and quantity of barbs were tested experimentally and numeric analysis was carried out to measure the volume of water collected and optimize the mass rate. The result shows that optimal fog collection is with a mass flow rate of 0.7433 g/min, with Li = 900 μm, θ = 45°, ϕ = 90°, Nb = 2, and Ns = 5. This study presents a sustainable and ecologically sound method for efficiently collecting humid air, which is expected to be advantageous for the advancement of future-oriented fog-collection, water-transportation, and separation technologies.