Ran Yu

Photocuring 3D printing faces challenges in achieving high mechanical strength and thermal stability primarily due to the low conversion degree of photopolymerization. This study presents a molecular design strategy to develop a high-performance, photothermal dual-curing resin for digital light processing (DLP) 3D printing. A polyurethane acrylate containing multiple hydrogen bonds and dynamic hindered urea bonds is synthesized and compounded with an acrylate-modified epoxy monomer, a reactive diluent, and a latent hindered urea curing agent to construct the hybrid system. During the photocuring stage, acrylate groups rapidly polymerize to form precise 3D structures. Subsequently, the latent agent dissociates upon heating and cures the epoxy groups, while the dynamic bonds on polyurethane acrylate dissociate to further increase cross-linking density. The synergy of hydrogen bonding, a rigid–flexible alternating microstructure, and high cross-linking density endows the cured material with superior overall performance. The optimized system achieves a tensile strength of 82.5 ± 3.6 MPa, an elongation at break of 9.5 ± 1.2%, and a glass transition temperature of 174.8 °C. Furthermore, it demonstrates excellent DLP printability for complex structures and outstanding shape memory performance. This work provides a promising pathway for fabricating high-performance structural components via vat photopolymerization 3D printing.

Bionic artificial skin which imitates the features and functions of human skin, has broad applications in wearable human‐machine interfaces. However, equipping artificial materials with skin‐like mechanical properties, self‐healing ability, and high sensitivity remains challenging. Here, inspired by the structure of human skin, an artificial skin based on ionogel composites with tailored mechanical properties and robust interface is prepared. Combining finite element analysis and direct ink writing (DIW) 3D printing technology, an ionogel composite with a rigid skeleton and an ionogel matrix is precisely designed and fabricated, realizing the mechanical anisotropy and nonlinear mechanical response that accurately mimic human skin. Robust interface is created through co‐curing of the skeleton and matrix resins, significantly enhancing the stability of the composite. The realization of self‐healing ability and resistance to crack growth further ensure the remarkable durability of the artificial skin for sensing application. In summary, the bionic artificial skin mimics the characteristics of human skin, including mechanical anisotropy, nonlinear mechanical response, self‐healing capability, durability and high sensitivity when applied as flexible sensors. These strategies provide strong support for the fabrication of tissue‐like materials with adaptive mechanical behaviors.

Meniscal implants with biomimetic 3D architecture, gradient mechanical properties, and excellent biocompatibility are urgently required due to the increasing incidence of meniscus injuries. Inspired by the microstructure of the meniscus, which consists of a meshwork interwoven with collagen fibers and a hydrophilic matrix filled with glycosaminoglycans and chondrocytes, here a type of structurally and functionally optimized meniscal scaffolds is prepared. Direct‐ink‐writing 3D printing technology is utilized to construct an elastomeric skeleton with a biomimetic 3D and gradient microstructure, and then hydrogel resin is infiltrated into the skeleton, resulting in an elastomer‐reinforced hydrogel composite meniscal scaffold through co‐curing of the elastomer and hydrogel resins. The composite meniscal scaffolds exhibit a highly porous structure and biomimetic gradient mechanical properties by controlling the ratio of elastomer and hydrogel materials. The co‐curing of the two materials creates robust interfaces through strong covalent bonding, ensuring their reliable long‐term mechanical performance. Furthermore, the coexistence of aqueous and oily phases of the emulsion‐type hydrogel resin allows the loading of both water‐soluble and lipid‐soluble drugs, endowing the composite scaffolds with a diphasic drug‐release capacity. The composite scaffolds are then implanted in the knee joints of beagle canines, successfully promoting the repair of meniscal injury and tissue regeneration.

Conductive nanomaterial/flexible polymer composite foams are of great interest in the field of flexible and wearable piezoresistive pressure sensors. However, the existing composite foam sensors are faced with stability issues from conductive nanomaterials, which tends to decrease their long-term durability. Herein, we developed a solvent evaporation-induced self-assembly strategy, which could significantly improve the stability of multiwalled carbon nanotubes (MWCNTs) on a silicone rubber foam skeleton. The process for self-assembly of MWCNTs was straightforward. Aqueous MWCNT dispersion droplets were first hierarchically enclosed in silicone rubber via water-in-oil (W/O) Pickering high internal phase emulsions (HIPEs). Then, the high pressure generated by fast evaporation of the solvent from the droplets could break the thinnest pore walls to form interconnected pores. As a result, very dense and firm MWCNT layers were self-assembled on the pore wall surface. Due to the excellent stability of MWCNTs and tetramodal interconnected porosity, our MWCNTs/silicone rubber composite foam showed the following "super" properties: low density of 0.26 g/mL, high porosity of 76%, and excellent mechanical strength (the maximum stress loss of 8.3% at 80% strain after 100 compression cycles). In addition, excellent piezoresistive performance, including superior discernibility for different amplitudes of compressive strain (up to 80%), rapid response time (150 ms), and high sensitivity (gauge factor of 1.44), was demonstrated for such foams, together with prominent durability (39,000 compression cycles at 60% strain in air) and excellent stability of resistance response in water and organic solvents (5000 compression cycles at 30% strain in water and ethanol). Regarding its application, a wearable piezoresistive sensor, which was assembled from the as-prepared conductive silicone rubber composite foam, could capture various movements from tiptoeing and finger bending to small deformations resulting from human pulse.

Osteoarthritis is a serious disease affecting joint cartilage. Owing to poor blood supply, the meniscus and acetabular labrum of joints heal poorly after injury. However, the development of artificial alternatives to these components that have similar mechanical properties and cartilage‐protection ability is challenging. In this study, a strong hydrogel with a biomimetic microstructure is prepared with an emulsion‐type photosensitive resin, where both hydrophilic and hydrophobic monomers, photo‐initiator, and drugs can be adopted. In this system, the hydrophobic monomer forms uniformly dispersed aggregates after curing, improving the mechanical properties of the hydrogel significantly. Furthermore, the coordination bonds between nontoxic Zr⁴⁺ cations and sulfonic acid groups prevent hydrogel swelling. In addition, the water–oil biphasic hydrogel ink enables the loading of water‐ and lipid‐soluble drugs, yielding hydrogel scaffolds with sustained dual‐drug release ability. Crucially, hydrogel scaffolds having excellent mechanical properties, low swelling, and sustained biphasic drug release ability can be prepared using digital light processing 3D printing technology, owing to the high curing rate of the hydrophobic photo‐initiator. These hydrogel scaffolds are applied as meniscal and labral replacements in a porcine model and show great promise for the prevention of secondary osteoarthritis, demonstrating the broad potential clinical applications of this material.

Ionogels are promising materials for flexible electronics due to their continuous conductive phase, high thermal and chemical stability. However, a large amount of ionic liquid is required to get high conductivity, resulting in a sharp decline in the mechanical properties. Therefore, it is a great challenge to prepare ionogels with both high conductivity and mechanical properties, which is important for their practical applications. Herein, ionogels with high mechanical strength and stretchability, extraordinary ionic conductivity, excellent transparency, outstanding durability, and stability are fabricated with crosslinked polymer, ionic liquid, and lithium salt. The adoption of lithium salt can significantly improve both the mechanical strength and stretchability, which is a common dilemma in material science, and simultaneously, address the conflict between mechanical strength and ionic conductivity in ionogels. It is primarily corresponding to the microphase‐separation effects induced by the lithium bonds formed between lithium ions and carbonyl groups on the polymer networks. Ionotronics including resistance‐type sensors for strain and temperature sensing and triboelectric nanogenerators with stable output performance are fabricated. Moreover, ionogel‐based microcircuit and sensing arrays with high resolution and accuracy are fabricated through digital light processing printing technology. The ionogels have great promise for various ionotronics in many fields.