Bioprinting has emerged as a flexible technology in tissue engineering to mimic biological and functional organizational complexity of native tissues. Drop-on-Demand (DoD) bioprinting is one of the most promising technologies currently due to the unique characteristics of high-throughput efficiency and cost-effectiveness. Despite these significant advantages, DoD bioprinting has some drawbacks, including loss of cell viability impacted by shear stress. However, there are only very few studies discussed the variation of shear stress in DoD cell printing and its effects on cell behaviours. In this paper, a CFD simulation model of piezoelectric DoD print-head was developed to study shear stress in the nozzle during printing. Experiments were conducted to study the effect of shear stress on cell viability and cell proliferation. The mathematical model of piezoelectric effect is developed with CFD model to improve the simulation accuracy. Parametric studies on shear stress were also carried out. Simulation results demonstrated that (1) shear stress has a dramatic variation around the nozzle orifice mainly during the rise time and the following dwell time of voltage pulse in the episode; (2) the backflow fluid pushed the fluid entered from the inlet flowing down along the wall, increasing the wall shear stress simultaneously; (3) voltage, viscosity and nozzle diameter have important effects on both values and the effect range of shear stress. With simulation results of shear stress, experiments showed that both cell viability and cell proliferation are decreased with the increase of shear stress, whereby shear stress has a larger influence on cell proliferation than on cell viability. Through the proposed simulation model, the computed shear stress during DoD bioprinting is able to link with engineering characteristics, such as printing parameters, and cell characteristics, such as cell viability and cell proliferation. The simulation model can be used to improve cell viability and cell proliferation through optimizing printing parameters to decrease shear stress in piezoelectric DoD bioprinting.

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Polyanionic compounds have large compositional flexibility, which creates a growing interest in exploring the property limits of electrode materials of rechargeable batteries. The realization of multisodium storage in the polyanionic electrodes can significantly improve capacity of the materials, but it often causes irreversible capacity loss and crystal phase evolution, especially under high-voltage operation, which remain important challenges for their application. Herein, it is shown that the multisodium storage in the polyanionic cathode can be enhanced and stabilized by increasing the entropy of the polyanionic host structure. The obtained polyanionic Na 3.4 Fe 0.4 Mn 0.4 V 0.4 Cr 0.4 Ti 0.4 (PO 4 ) 3 cathode exhibits multicationic redox property to achieve high capacity with good reversibility under the high voltage of 4.5 V (vs Na/Na + ). Exploring the underlying mechanism through operando characterizations, a stable trigonal phase with reduced volume change during the multisodium storage process is disclosed. Besides, the enhanced performance of the HE material also derives from the synergistic effect of the diverse TM species with suitable molarity. These results reveal the effectiveness of high-entropy concept in expediting high-performance polyanionic cathodes discovery.

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Li5FeO4, as a high-capacity built-in pre-lithiation reagent, has attracted wide interest due to its attractive characteristics, such as extremely higher capacity and energy density, low cost, and environmental friendliness. However, the preparation technology of high-stability Li5FeO4 remains a great challenge. Here, we report a highly air-stable Li5FeO4 cathode pre-lithiation reagent by the solid-phase method. The Li5FeO4 is coated with Li6CoO4 (Li6CoO4@Li5FeO4, referred to as LCO@LFO), which can effectively improve the stability of Li5FeO4 materials under ambient atmosphere and significantly enhance the electrochemical performance. The material possesses an initial charge capacity of 518.8mAh g−1 when charged to 4.5 V and exhibits good air-filled capacity retention. Besides, the LiNi0.8Co0.1Mn0.1O2 (NCM811) full-cell with 5 wt% LCO@LFO additive has an initial discharging capacity of 205 mAh g−1 in the charge and discharge interval of 2.0 V–4.5 V (vs Li+/Li), respectively, higher than the initial discharging capacity of 166.5 mAh g−1 of pure NCM811. The reversible specific capacity of the NCM811 with LCO@LFO cathode in the full cell can be increased by 8.8%, which is equivalent to a 14.35% increase in energy density. Our research report opens a door for the commercial application of LCO@LFO, a high-stability cathode composite pre-lithiation reagent.