There is a great challenge in regenerating osteochondral defects because they involve lesions of both cartilage and subchondral bone, which have remarkable differences in their chemical compositions and biological lineages. Thus, considering the complicated requirements in osteochondral reconstruction, a biomimetic biphasic osteochondral scaffold (BBOS) with the layer-specific release of stem cell differentiation inducers are developed. The cartilage regeneration layer (cartilage scaffold, CS) in the BBOS contains a hyaluronic acid hydrogel to mimic the composition of cartilage, which is mechanically enhanced by host-guest supramolecular units to control the release of kartogenin (KGN). Additionally, a 3D-printed hydroxyapatite (HAp) scaffold releasing alendronate (ALN) is employed as the bone-regeneration layer (bone scaffold, BS). The two layers are bound by semi-immersion and could regulate the hierarchical targeted differentiation behavior of the stem cells. Compared to the drug-free scaffold, the MSCs in the BBOS could be promoted to differentiate into both chondrocytes and osteoblasts. The in vivo results demonstrate the strong promotion of cartilage or bone regeneration in their respective layers. It is expected that this BBOS with layer-specific inducer release can become a new strategy for osteochondral regeneration.

Synthetic hydrogels are unique tissue mimics but rarely reproduce the strain‐stiffening properties of native tissues. This mechanical mismatch impairs the performance of hydrogels in practical applications. Inspired by the crimped structure of collagenous tissues, a series of strain‐stiffening hydrogels composed of curved parallel fibers are developed. These fibers are constructed from a bundle of intertwisted nanofibrils composed of short alkyl side chain‐modified polymer chains. This hierarchical organization enables exquisitely cascaded deformation that facilitates soft‐to‐firm and resilience‐to‐viscoelasticity transitions, thus synergically mimicking the strain‐adaptive stiffening and damping behaviors of natural tissues. Together with structural evolution and a constitutive model, rationally tuning the tortuosity and flexibility of the curved fibers produces a diverse combination of strain‐stiffening properties and unprecedented penetration into the regions of several tissues. The crimped structure and the resultant stiffening properties constitute major improvements to nanofiber‐based scaffolds for use in collagenous tissue repair.

Triply periodic minimum surfaces (TPMS), which outperform other structures in terms of bulk moduli and relative density, have been widely used to dramatically improve the mechanical strength of natural echinoderm skeletons and engineered scaffolds. Herein, TPMS‐structure‐based 3D‐printed hydroxyapatite (HAp) scaffolds to highly improve their limited mechanical strength and evaluate the underlying mechanism in terms of mechanical match and biological bone repair process as a bone regeneration scaffold are constructed. The results show that TPMS‐structure‐based HAp scaffolds have a greater compressive strength range that is sufficient to meet the strength requirements for human cortical and trabecular bone, and outperform traditional HAp scaffolds with Cross‐hatch structures in terms of compressive strength, cell density, and osteogenic differentiation. The reduction of stress concentration and open‐cell permeable structure of Split‐P scaffolds can benefit the generation and ingrowth of new bone after the in vivo implantation in the rabbit femur bone. Furthermore, RNA‐seq and immunochemistry staining results of in vivo samples unravel the bone repair mechanism in a time sequence. The optimized scaffolds with TPMS macrostructures and an in‐depth understanding of repair mechanisms will contribute to the development of bone regeneration materials that perform on par with load‐bearing bone.

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In order to avoid the high energy consumption in SO 2 capture with aqueous amine absorbents, a liquid− liquid SO 2 phase-change absorbent (SPCA) was developed in the present work using N,N-dimethylaniline (DMA) as absorbent, and high-boiling liquid paraffin was used as solvent to adjust the boiling point of the solution. The homogeneous solution would form two immiscible liquid phases after SO 2 bubbling, only the SO 2 -rich phase needed to be desorbed, which could effectively reduce the energy consumption. Different from the liquid−solid phase-change absorbents developed in our previous work, the liquid−liquid phasechange absorbent avoid their shortcomings such as difficulties in separation of absorption products. The absorption product of SPCA was proved to be a charge-transfer complex DMA•SO 2 by NMR and FTIR characterization, and the phase-change mechanism was attributed to the polarity variation between DMA and DMA•SO 2 . The viscosities of SPCAs was lower than 11.65 mPa•s, and the viscosity of SO 2 -rich phase was 3.9 mPa•s at 30 °C. The mass absorption capacity was found to be 0.89 g SO 2 /g DMA at 1 atm and 20 °C by ignoring liquid paraffin. The SPCA exhibited extremely high mass selectivity of SO 2 /CO 2 with the value of 351. In addition, it was found that water had no effect on the structure of the absorption product and the SO 2 capacity of SPCA. SPCA could be completely regenerated in 50 min at 80 °C. All the results showed that the SPCAs composed of DMA/liquid paraffin have a good application prospect.

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Removal of sulfur dioxide (SO2) from flue gas by developing a highly efficient phase-change absorption solution is an effective way to tackle increasingly serious air pollution problems. In this study, the phase-change absorption behaviors of SO2 by using low cost 2-(diethylamino)­ethanol (DEEA)/hexadecane as absorbent/solvent was systematically studied. The homogeneous solution could be facilely and quickly changed into two immiscible liquid phases upon introducing low partial pressure SO2. The liquid–liquid phase-change phenomenon was attributed to the formation of zwitterionic product by the reaction of DEEA with SO2, which was insoluble in low polarity hexadecane. Specifically, the absorption capacity of DEEA toward SO2 under 20 °C could reach 0.51 and 1.56 g of SO2/g of DEEA at 0.02 and 1 atm, respectively, which exhibited front-rank absorption capacity to most reported works. In addition, it was suggested that the present absorbent exhibited a highly selective absorption property and high removal efficiency of SO2. The well-matched absorbent/solvent phase-change system holds a promising application in the treatment of industrial flue gases.

As phase change absorption of CO2 could drastically reduce energy consumption, a liquid–liquid phase change absorption process of SO2 was developed in the present work using N,N-dimethylethanolamine (DMEA) as absorbent and hexadecane as solvent. The homogeneous solution was split into two immiscible phases when the absorption capacity reached 0.02 mol/mol. The phase change mechanism was attributed to the formation of a zwitterionic compound, through the reaction of SO2 with DMEA and its separation from the solution. The viscosity of the absorption product was related to the absorption capacity and temperature, which is described by an Arrhenius-type equation. The gravimetric absorption capacity was found to be 1.56 g SO2/g DMEA at 1.0 atm, which is the highest value reported in the literature. At 0.02 atm, its capacity still reached 0.59 g/g, which is also much higher than those of other absorbents at similar conditions. The distribution of DMEA, hexadecane, and SO2 in the two phases is described by two differential equations and material balance. Ternary phase diagram representation was used to provide an intuitive visual of the phase separation behavior. High temperature was found to play a role in weakening phase separation. Ultimately, DMEA was chemically regenerated by the reaction of the absorption product and cyclohexene oxide.