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4D printing has attracted widespread attention due to its ability to fabricate complex structures capable of responding to specific stimuli. However, existing smart materials used for 4D printing, such as conventional hydrogels, liquid crystal elastomers, and shape‐memory polymers, are constrained in their ability to fulfill both mechanical ultrastrength and ultrastretchability requirements simultaneously due to their water saturation or uneven network structures. This study presents 4D printing of liquid‐free ionic elastomers (LFIEs) that is achieved through photopolymerization of the acrylic acid‐tetramethylammonium chloride‐polymerizable deep eutectic solvent. The transition temperature (Tt) of the high‐fracture‐strength LFIEs is adjusted by introducing phenylphosphoric acid, harboring multiple hydrogen‐bonds, leading to improved molecular chain mobility through softening of the chains. Consequently, the 4D‐printed LFIEs retain their high strength while achieving ultrastretchable properties even under elevated temperatures during heating. Moreover, the 4D‐printed LFIEs demonstrate both a swift response time and a high fixation rate even after undergoing repeated transformation cycles. These outstanding capabilities exhibit by LFIEs present a reliable strategy for advancing their applications in diverse fields, such as smart furniture, robotics, and intelligent manufacturing with remote monitoring, and beyond. [ABSTRACT FROM AUTHOR]

Wireless energy transfer (WET) based on ultrasound‐driven generators with enormous beneficial functions, is technologically in progress by the valuation of ultrasonic metamaterials (UMMs) in science and engineering domains. Indeed, novel metamaterial structures can develop the efficiency of mechanical and physical features of ultrasound energy receivers (US‐ETs), including ultrasound‐driven piezoelectric and triboelectric nanogenerators (US‐PENGs and US‐TENGs) for advantageous applications. This review article first summarizes the fundamentals, classification, and design engineering of UMMs after introducing ultrasound energy for WET technology. In addition to addressing using UMMs, the topical progress of innovative UMMs in US‐ETs is conceptually presented. Moreover, the advanced approaches of metamaterials are reported in the categorized applications of US‐PENGs and US‐TENGs. Finally, some current perspectives and encounters of UMMs in US‐ETs are offered. With this objective in mind, this review explores the potential revolution of reliable integrated energy transfer systems through the transformation of metamaterials into ultrasound‐driven active mediums for generators. [ABSTRACT FROM AUTHOR]

Three‐dimensional (3D) printing is an emerging technique that has shown promising success in engineering human tissues in recent years. Further development of vat‐photopolymerization printing modalities has significantly enhanced the complexity level for 3D printing of various functional structures and components. Similarly, the development of microfluidic chip systems is an emerging research sector with promising medical applications. This work demonstrates the coupling of a digital light processing (DLP) printing procedure with a microfluidic chip system to produce size‐tunable, 3D‐printable porosities with narrow pore size distributions within a gelatin methacryloyl (GelMA) hydrogel matrix. It is found that the generation of size‐tunable gas bubbles trapped within an aqueous GelMA hydrogel‐precursor can be controlled with high precision. Furthermore, the porosities are printed in two‐dimensional (2D) as well as in 3D using the DLP printer. In addition, the cytocompatibility of the printed porous scaffolds is investigated using fibroblasts, where high cell viabilities as well as cell proliferation, spreading, and migration are confirmed. It is anticipated that the strategy is widely applicable in a range of application areas such as tissue engineering and regenerative medicine, among others. [ABSTRACT FROM AUTHOR]

With the rapid development and popularization of additive manufacturing, different technologies, including, but not limited to, extrusion-, droplet-, and vat-photopolymerization-based fabrication techniques, have emerged that have allowed tremendous progress in three-dimensional (3D) printing in the past decades. Bioprinting, typically using living cells and/or biomaterials conformed by different printing modalities, has produced functional tissues. As a subclass of vat-photopolymerization bioprinting, digital light processing (DLP) uses digitally controlled photomasks to selectively solidify liquid photocurable bioinks to construct complex physical objects in a layer-by-layer manner. DLP bioprinting presents unique advantages, including short printing times, relatively low manufacturing costs, and decently high resolutions, allowing users to achieve significant progress in the bioprinting of tissue-like complex structures. Nevertheless, the need to accommodate different materials while bioprinting and improve the printing performance has driven the rapid progress in DLP bioprinters, which requires multiple pieces of knowledge ranging from optics, electronics, software, and materials beyond the biological aspects. This raises the need for a comprehensive review to recapitulate the most important considerations in the design and assembly of DLP bioprinters. This review begins with analyzing unique considerations and specific examples in the hardware, including the resin vat, optical system, and electronics. In the software, the workflow is analyzed, including the parameters to be considered for the control of the bioprinter and the voxelizing/slicing algorithm. In addition, we briefly discuss the material requirements for DLP bioprinting. Then, we provide a section with best practices and maintenance of a do-it-yourself DLP bioprinter. Finally, we highlight the future outlooks of the DLP technology and their critical role in directing the future of bioprinting. The state-of-the-art progress in DLP bioprinter in this review will provide a set of knowledge for innovative DLP bioprinter designs., Competing Interests: YSZ consulted for Allevi by 3D systems, and sits on the scientific advisory board and holds options of Xellar, neither of which, however, participated in or bias the work. The interests are managed by the Brigham and Women's Hospital. The other authors declare no COI., (© 2024 Author(s).)

Current biofabrication strategies are limited in their ability to replicate native shape-to-function relationships, that are dependent on adequate biomimicry of macroscale shape as well as size and microscale spatial heterogeneity, within cell-laden hydrogels. In this study, a novel diffusion-based microfluidics platform is presented that meets these needs in a two-step process. In the first step, a hydrogel-precursor solution is dispersed into a continuous oil phase within the microfluidics tubing. By adjusting the dispersed and oil phase flow rates, the physical architecture of hydrogel-precursor phases can be adjusted to generate spherical and plug-like structures, as well as continuous meter-long hydrogel-precursor phases (up to 1.75 m). The second step involves the controlled introduction a small molecule-containing aqueous phase through a T-shaped tube connector to enable controlled small molecule diffusion across the interface of the aqueous phase and hydrogel-precursor. Application of this system is demonstrated by diffusing co-initiator sodium persulfate (SPS) into hydrogel-precursor solutions, where the controlled SPS diffusion into the hydrogel-precursor and subsequent photo-polymerization allows for the formation of unique radial stiffness patterns across the shape- and size-controlled hydrogels, as well as allowing the formation of hollow hydrogels with controllable internal architectures. Mesenchymal stromal cells are successfully encapsulated within hollow hydrogels and hydrogels containing radial stiffness gradient and found to respond to the heterogeneity in stiffness through the yes-associated protein mechano-regulator. Finally, breast cancer cells are found to phenotypically switch in response to stiffness gradients, causing a shift in their ability to aggregate, which may have implications for metastasis. The diffusion-based microfluidics thus finds application mimicking native shape-to-function relationship in the context of tissue engineering and provides a platform to further study the roles of micro- and macroscale architectural features that exist within native tissues., (Creative Commons Attribution license.)

In situ additive biomanufacturing of structures may boost regenerative medicine.