Durable,Sensitive, and Wide‐Range Wearable Pressure Sensors Based on Wavy‐Structured Flexible Conductive Composite Film

Flexible pressure sensors have potential applications in human motion monitoring and electronic skins. To satisfy the practical applications, pressure sensors with a high sensitivity, a low detection limit, a broad response range, and an excellent stability are highly needed. Here, a piezoresistive pressure sensor based on wavy‐structured single‐walled carbon nanotube/graphite flake/thermoplastic polyurethane (SWCNT/GF/TPU) composite film is fabricated by a prestretching process. Due to the random wavy structure, high conductivity, and good flexibility, the prepared sensor displays a low detection limit of 2 Pa, a wide sensing range of 0–60 kPa, and a high sensitivity of 5.49 kPa^?1 for 0–50 Pa. Furthermore, the sensor shows a remarkable repeatability of over 1.1 × 10⁴, 9.0 × 10³, and 2.0 × 10³ pressure loading/unloading cycles at 50 Pa, 500 Pa, and 30 kPa, respectively, and a fast responsibility of 100–150 ms of loading response time and 400–600 ms of relaxation time. Therefore, the pressure sensor is successfully adopted to monitor both the large‐scale human activities (e.g., walk and jump) and the small‐scale signals (e.g., wrist pulse). Furthermore, a sensor array is assembled to map the weight and shape of an object, indicating its various potential applications including human–machine interactions, human health monitoring, and other wearable electronics.     

铜基正弦波微通道内流动沸腾传热特性试验研究

基于超快激光技术加工铜基正弦波弯曲型微通道,以去离子水为流动工质,在不同质量流量和热通量条件下,对弯曲型微通道内流动沸腾特性进行试验研究。基于温度/压力数据和流动可视化结果,发现通道传热系数随出口干度增大,呈迅速增大后减小并趋于稳定趋势,正弦波微通道相较直微通道具有更好的换热性能,传热系数最大提高127.7%,压降仅增加14.4%。波状通道结构能明显抑制流动沸腾中不稳定现象发生。通过可视化试验发现,随热通量增大,流型经历泡状流-弹状流-环状流的转变,换热主导机制由核态沸腾逐渐过渡到薄液膜蒸发。     

Fenton试剂对剩余污泥脱水性能的改善

研究了利用Fenton试剂调理城市污水处理厂剩余污泥,通过测定污泥毛细吸水时间(CST)、污泥比阻(SRF)和泥饼含水率来表征污泥脱水性能的变化,分别考察了污泥初始pH、H2O2投加量、H2O2/Fe2+、反应温度和反应时间对污泥调理效果的影响。综合考虑,确定Fenton调理污泥的最佳条件为:pH=3、抽滤脱水和离心脱水H2O2最佳投加量分别为3 g/L和9 g/L、H2O2/Fe2(+质量比)最佳范围为8～12、反应温度50℃、反应时间60 min。对污泥离心上清液中胞外聚合物(EPS)含量的研究表明,Fenton调理后污泥上清液中蛋白质和多糖含量有大幅升高,说明Fenton试剂能有效氧化破解EPS,从而提高污泥的絮凝性,改善污泥的脱水性能。Fenton氧化后污泥颗粒粒径变小,比表面积增大。     

UHMWPE/HDPE/纳米SiO2共混体系的毛细管挤出流变行为

采用毛细管流变仪,研究了超高分子量聚乙烯(UHMWPE)/高密度聚乙烯(HDPE)/纳米二氧化硅(SiO2)共混体系,及其对照组的流变行为和挤出过程中的不稳定流动现象,分析了共混物发生鲨鱼皮畸变和整体破裂的临界剪切应力和临界剪切速率的变化情况。结果表明,经过偶联剂改性的纳米SiO2粒子,在PE基质的共混体系中存在一定的界面黏附作用,降低了纳米共混体系的挤出胀大比,弹性特征减轻。这种界面相互作用限制了纳米共混材料在口模区域的黏性流动以及分子链离开口模后的构象恢复,降低了发生流动不稳定现象的临界剪切速率,发生鲨鱼皮畸变的临界剪切应力增大,整体破裂后,形成交替出现"鲨鱼皮-破裂"的振荡性变化外观。     

A capillary bundle model for the forced imbibition in the shale matrix with dual-wettability

The forced imbibition during hydraulic fracturing is one of the main mechanisms of oil production in shale oil reservoirs. However, the shale matrix has complex structures of nanopores and is rich in organic matters. The wettability of nanopores in organics matters is different from the nanopores in inorganic matters, and the characteristic of dual-wettability leads to complex mechanisms of forced imbibition. This paper proposes a model for describing the imbibition in a dual-wettability shale oil reservoir based on the capillary tube model. The external displacement pressure gradient is also considered to study the forced and spontaneous imbibition of hydraulic fracturing liquid into oil-wet organic nanopores and water-wet inorganic nanopores. The slip effect in organic nanopores and the boundary-layer effect in inorganic nanopores are considered in this model. The analytical expressions for describing the location of the oil–water imbibition front in an oil-wet organic nanopore and a water-wet inorganic nanopore are derived, respectively. The semi-analytical solution for predicting flow rate in a shale core with an external pressure gradient is given and demonstrated with a case study.     

pH-Responsive and Reversible A-Motif-Based DNA Hydrogel: Synthesis and Biosensing Application**

Functional DNA hydrogels with various motifs and functional groups require perfect sequence design to avoid cross-bonding interference with themselves or other structural sequences. This work reports an A-motif functional DNA hydrogel that does not require any sequence design. A-motif DNA is a noncanonical parallel DNA duplex structure containing homopolymeric deoxyadenosines (poly-dA) strands that undergo conformation changes from single strands at neutral pH to a parallel duplex DNA helix at acidic pH. Despite this and other advantages over other DNA motifs like no cross-bonding interference with other structural sequences, the A-motif has not been explored much. We successfully synthesized a DNA hydrogel by using an A-motif as a reversible handle to polymerize a DNA three-way junction. The A-motif hydrogel was initially characterized by electrophoretic mobility shift assay, and dynamic light scattering, which showed the formation of higher-order structures. Further, we used imaging techniques like atomic force microscopy and scanning electron microscope to validating its hydrogel like highly branched morphology. pH-induced conformation transformation from monomers to gel is quick and reversible, and was analysed for multiple acid-base cycles. The sol-to-gel transitions and gelation properties were further examined in rheological studies. The use of the A-motif hydrogel in the visual detection of pathogenic target nucleic acid sequence was demonstrated for the first time in a capillary assay. Moreover, pH-induced hydrogel formation was observed in situ as a layer over the mammalian cells. The proposed A-motif DNA scaffold has enormous potential in designing stimuli-responsive nanostructures that can be used for many biological applications.     

Janus particle amphiphilicity and capillary interactions at a fluid interface

Studying the behavior of anisotropic particles at fluid interfaces is a rapidly expanding field, as understanding how the introduced anisotropy affects the resulting properties is essential in the engineering of interfacial systems. Surface anisotropic particles, also known as Janus particles (JPs), offer new possibilities for novel applications due to their amphiphilicity and stronger binding to fluid interfaces compared to homogeneous particles. Introducing surface anisotropy creates complexity as the orientation of interfacially bound particles affects interparticle interactions, a contributing factor to the microstructure formation. In this work, we have investigated the microstructure of JP monolayers formed at the air–water interface using particles with different degrees of amphiphilicity and examined the response of the networks to applied compressions. Our findings demonstrate that JPs amphiphilicity is a crucial factor governing their orientation at the interface, which in turn dictates the complexity of the capillary interactions present and the mechanical properties of the ensuing networks.     

The capillary and thermal performance of the porous silicon nitride ceramics with nearly spherical pore structure

The capillary and thermal performance of porous Si₃N₄ ceramics with nearly spherical pore structure has been investigated by altering the addition and diameter of pore-forming agent polymethyl methacrylate (PMMA) in this work. An exponential model is used to evaluate the liquid uptake capacity of porous Si₃N₄ ceramics. Porous Si₃N₄ ceramics fabricated by 5 μm PMMA with 40 wt.% addition possess the lowest capillary time constant and show the best capillary performance owing to the perfect balance between friction resistance and capillary force. The thermal conductivity of porous Si₃N₄ ceramics is significantly impacted by their porosity. Alexander model with an exponent of .96 is suitable for predicting the thermal conductivity of porous Si₃N₄ ceramics due to its R-squared up to .99. Moreover, with the addition and diameter of PMMA decrease, the flexural strength of porous Si₃N₄ ceramics increases. These results support the application of porous Si₃N₄ ceramics in the field of mass and heat transfer.     

毛细管气相色谱法测定甘蔗渣水解液中的糖含量

讨论了采用衍生化 -萃取法处理含糖样品 ,毛细管气相色谱测定甘蔗渣水解液中糖含量的方法。对样品的衍生化反应时间、萃取时间和衍生化试剂用量对回收率的影响进行了详细的讨论。结果表明 ,方法简便、可靠。方法的相对标准偏差小于 4%。     

气相色谱法分析正丁醛

采用HP 1毛细管色谱柱 (2 5m× 0 .32mmi.d .× 1.0 5 μm)对正丁醛及其各种组份进行了气相色谱分析方法的研究。结果表明 :该毛细管柱能够很好的分离正丁醛 ,其异丁醛、正丁醇、正丁酸的检出限分别是5 0ng ,15ng和 10 0ng ,线性范围为 5 0ng～ 5 0 0ng。