Since the late 1980s, additive manufacturing (AM), commonly known as three-dimensional (3D) printing, has been gradually popularized. However, the microstructures fabricated using 3D printing is static. To overcome this challenge, four-dimensional (4D) printing which defined as fabricating a complex spontaneous structure that changes with time respond in an intended manner to external stimuli. 4D printing originates in 3D printing, but beyond 3D printing. Although 4D printing is mainly based on 3D printing and become an branch of additive manufacturing, the fabricated objects are no longer static and can be transformed into complex structures by changing the size, shape, property and functionality under external stimuli, which makes 3D printing alive. Herein, recent major progresses in 4D printing are reviewed, including AM technologies for 4D printing, stimulation method, materials and applications. In addition, the current challenges and future prospects of 4D printing were highlighted.
The rapid development of large language models has revolutionized code intelligence in software development. However, the predominance of closed-source models has restricted extensive research and development. To address this, we introduce the DeepSeek-Coder series, a range of open-source code models with sizes from 1.3B to 33B, trained from scratch on 2 trillion tokens. These models are pre-trained on a high-quality project-level code corpus and employ a fill-in-the-blank task with a 16K window to enhance code generation and infilling. Our extensive evaluations demonstrate that DeepSeek-Coder not only achieves state-of-the-art performance among open-source code models across multiple benchmarks but also surpasses existing closed-source models like Codex and GPT-3.5. Furthermore, DeepSeek-Coder models are under a permissive license that allows for both research and unrestricted commercial use.
Transitional metal oxides have been explored as next generation anode materials for lithium ion battery due to their much higher capacity (~1000 mAh/g) than graphite (372 mAh/g). However, the large volume expansion comes out of lithiation process as well as the relative low conductivity of metal oxides hinder the cycle and rate performance. It is believed these problems can be accommodated by the carbon-hybrid nanostructured metal oxide. Metal-organic framework (MOF) was recently used to prepare advanced transition metal oxide electrodes due to the capability of forming a well-organized nanostructure. By thermal annealing MOF materials, carbon-coated transition metal oxide with the desired structure can be achieved in a facile manner. Here in this work, nickel based MOFs (Ni-MOFs) with hollow ball-in-ball structure were synthesized via a facile solvothermal reaction. Nickel nitrate hexahydrate, trimesic acid and polyvinylpyrrolidone (PVP) were used as metal ions source, organic ligand and stabilizing agent, respectively. A mixture of ethanol, N,N -dimethylformamide (DMF) and water was used as solvent. The resulting hollow structures were particularly interesting as they exhibited the excellent performance to mitigate the volume expansion. The resulting In order to convert the Ni-MOFs into conductive electrode materials, a two-step thermal annealing process was carried out and the hierarchical NiO/Ni/Graphene nanostructured materials were obtained: Firstly, graphene covered nickel nanoparticles were formed by annealing the Ni-MOFs samples under inert gas environment. During this procedure, the organic ligand can be carbonized and converted into graphene layers due to the catalysis of Ni nanoparticles. Subsequently, the nickel nanoparticles were converted into NiO/Ni complex nanoparticles by annealing the samples in air. The microspherical structure from the Ni-MOFs was intact throughout the annealing process. This hierarchical NiO/Ni/Graphene nanomaterial is an ideal anode material for the high-performance lithium-ion battery: it possesses a highly porous, hollow structure articulated with ultrafine transition metal oxide nanoparticles with conformal graphene coating. These features enable the electrode made from this material to have not only high specific capacity, but also stable SEI, excellent electrical conductivity and robust structure. As expected, The NiO/Ni/graphene anode exhibited high reversible specific capacity (1144 mAh/g), excellent cyclability (no significant capacity fading after 1000 cycles at 2 A/g) and ratability (805 mAh/g at 15 A/g) Additionally, these hierarchical nanomaterials were used in the anode of a sodium-ion battery (SIB), which is an attractive low-cost solution for a rechargeable electrochemical energy storage system. The initial investigation of the sodium ion battery in this work indicated that the hierarchical NiO/Ni/Graphene nanomaterial is also a promising anode for the sodium ion battery. The SIBs with NiO/Ni/graphene anode exhibited good cycle stability (0.2% specific capacity fading per cycle) and ratability (207 mAh/g at 2 A/g). Figure 1
Optogenetically engineered cell population obtained by heterogeneous gene expression plays a vital role in life science, medicine, and biohybrid robotics, and purification and characterization are essential to enhance its application performance. However, the existing cell purification methods suffer from complex sample preparation or inevitable damage and pollution. The efficient and nondestructive label-free purification and characterization of the optogenetically engineered cells, HEK293-ChR2 cells, is provided here using an optically-induced dielectrophoresis (ODEP)-based approach. The distinctive crossover frequencies of the engineered cells and the unmodified cells enable effective separation due to the opposite DEP forces on them. The ODEP-based approach can greatly improve the purity of the separated cell population and especially, the ratio of the engineered cells in the separated cell population can be enhanced by 275% at a low transfection rate. The size and the membrane capacitance of the separated cell population decreases and increases, respectively, as the ratio of the engineered cells grows in the cell population, indicating that successful expression of ChR2 in a single HEK293 cell makes its size and membrane capacitance smaller and larger, respectively. The results of biohybrid imaging with the optogenetically engineered cells demonstrated that cell purification can improve the imaging quality. This work proves that the separation and purification of engineered cells are of great significance for their application in practice.
Gene transfection is an important technology for various biological applications. The exogenous DNA is commonly delivered into cells by using a strong electrical field to form transient pores in cellular membranes. However, the high voltage required in this electroporation process may cause cell damage. In this study, a dielectrophoretically-assisted electroporation was developed by using light-activated virtual microelectrodes in a new microfluidic platform. The DNA electrotransfection used a low applied voltage and an alternating current to enable electroporation and transfection. Single or triple fluorescence-carrying plasmids were effectively transfected into various types of mammalian cells, and the fluorescent proteins were successfully expressed in live transfected cells. Moreover, the multi-triangle optical pattern that was projected onto a photoconductive layer to generate localized non-uniform virtual electric fields was found to have high transfection efficiency. The developed dielectrophoretically-assisted electroporation platform may provide a simpler system for gene transfection and could be widely applied in many biotechnological fields.
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