High Throughput‐Per‐Footprint Inertial Focusing

Matching the scale of microfluidic flow systems with that of microelectronic chips for realizing monolithically integrated systems still needs to be accomplished. However, this is appealing only if such re‐scaling does not compromise the fluidic throughput. This is related to the fact that the cost of microelectronic circuits primarily depends on the layout footprint, while the performance of many microfluidic systems, like flow cytometers, is measured by the throughput. The simple operation of inertial particle focusing makes it a promising technique for use in such integrated flow cytometer applications, however, microfluidic footprints demonstrated so far preclude monolithic integration. Here, the scaling limits of throughput‐per‐footprint (TPFP) in using inertial focusing are explored by studying the interplay between theory, the effect of channel Reynolds numbers up to 1500 on focusing, the entry length for the laminar flow to develop, and pressure resistance of the microchannels. Inertial particle focusing is demonstrated with a TPFP up to 0.3 L/(min cm²) in high aspect‐ratio rectangular microfluidic channels that are readily fabricated with a post‐CMOS integratable process, suggesting at least a 100‐fold improvement compared to previously demonstrated techniques. Not only can this be an enabling technology for realizing cost‐effective monolithically integrated flow cytometry devices, but the methodology represented here can also open perspectives for miniaturization of many biomedical microfluidic applications requiring monolithic integration with microelectronics without compromising the throughput.     

Beyond Activated Carbon: Graphite‐Cathode‐Derived Li‐Ion Pseudocapacitors with High Energy and High Power Densities

Supercapacitors have aroused considerable attention due to their high power capability, which enables charge storage/output in minutes or even seconds. However, to achieve a high energy density in a supercapacitor has been a long‐standing challenge. Here, graphite is reported as a high‐energy alternative to the frequently used activated carbon (AC) cathode for supercapacitor application due to its unique Faradaic pseudocapacitive anion intercalation behavior. The graphite cathode manifests both higher gravimetric and volumetric energy density (498 Wh kg^?1 and 431.2 Wh l^?1) than an AC cathode (234 Wh kg^?1 and 83.5 Wh l^?1) with peak power densities of 43.6 kW kg^?1 and 37.75 kW l^?1. A new type of Li‐ion pseudocapacitor (LIpC) is thus proposed and demonstrated with graphite as cathode and prelithiated graphite or Li₄Ti₅O₁₂ (LTO) as anode. The resultant graphite–graphite LIpCs deliver high energy densities of 167–233 Wh kg^?1 at power densities of 0.22–21.0 kW kg^?1 (based on active mass in both electrodes), much higher than 20–146 Wh kg^?1 of AC‐derived Li‐ion capacitors and 23–67 Wh kg^?1 of state‐of‐the‐art metal oxide pseudocapacitors. Excellent rate capability and cycling stability are further demonstrated for LTO‐graphite LIpCs.     

Chemically Prelithiated Hard‐Carbon Anode for High Power and High Capacity Li‐Ion Batteries

Hard carbons (HC) have potential high capacities and power capability, prospectively serving as an alternative anode material for Li‐ion batteries (LIB). However, their low initial coulombic efficiency (ICE) and the resulting poor cyclability hinder their practical applications. Herein, a facile and effective approach is developed to prelithiate hard carbons by a spontaneous chemical reaction with lithium naphthalenide (Li‐Naph). Due to the mild reactivity and strong lithiation ability of Li‐Naph, HC anode can be prelithiated rapidly in a few minutes and controllably to a desirable level by tuning the reaction time. The as‐formed prelithiated hard carbon (pHC) has a thinner, denser, and more robust solid electrolyte interface layer consisting of uniformly distributed LiF, thus demonstrating a very high ICE, high power, and stable cyclability. When paired with the current commercial LiCoO₂ and LiFePO₄ cathodes, the assembled pHC/LiCoO₂ and pHC/LiFePO₄ full cells exhibit a high ICE of >95.0% and a nearly 100% utilization of electrode‐active materials, confirming a practical application of pHC for a new generation of high capacity and high power LIBs.     

A Silica‐Aerogel‐Reinforced Composite Polymer Electrolyte with High Ionic Conductivity and High Modulus

High‐energy all‐solid‐state lithium (Li) batteries have great potential as next‐generation energy‐storage devices. Among all choices of electrolytes, polymer‐based systems have attracted widespread attention due to their low density, low cost, and excellent processability. However, they are generally mechanically too weak to effectively suppress Li dendrites and have lower ionic conductivity for reasonable kinetics at ambient temperature. Herein, an ultrastrong reinforced composite polymer electrolyte (CPE) is successfully designed and fabricated by introducing a stiff mesoporous SiO₂ aerogel as the backbone for a polymer‐based electrolyte. The interconnected SiO₂ aerogel not only performs as a strong backbone strengthening the whole composite, but also offers large and continuous surfaces for strong anion adsorption, which produces a highly conductive pathway across the composite. As a consequence, a high modulus of ≈0.43 GPa and high ionic conductivity of ≈0.6 mS cm^?1 at 30 °C are simultaneously achieved. Furthermore, LiFePO₄–Li full cells with good cyclability and rate capability at ambient temperature are obtained. Full cells with cathode capacity up to 2.1 mAh cm^?2 are also demonstrated. The aerogel‐reinforced CPE represents a new design principle for solid‐state electrolytes and offers opportunities for future all‐solid‐state Li batteries.     

Point‐Defect‐Passivated MoS2 Nanosheet‐Based High Performance Piezoelectric Nanogenerator

In this work, a sulfur (S) vacancy passivated monolayer MoS₂ piezoelectric nanogenerator (PNG) is demonstrated, and its properties before and after S treatment are compared to investigate the effect of passivating S vacancy. The S vacancies are effectively passivated by using the S treatment process on the pristine MoS₂ surface. The S vacancy site has a tendency to covalently bond with S functional groups; therefore, by capturing free electrons, a S atom will form a chemisorbed bond with the S vacancy site of MoS₂. S treatment reduces the charge‐carrier density of the monolayer MoS₂ surface, thus the screening effect of piezoelectric polarization charges by free carrier is significantly prevented. As a result, the output peak current and voltage of the S‐treated monolayer MoS₂ nanosheet PNG are increased by more than 3 times (100 pA) and 2 times (22 mV), respectively. Further, the S treatment increases the maximum power by almost 10 times. The results suggest that S treatment can reduce free‐charge carrier by sulfur S passivation and efficiently prevent the screening effect. Thus, the piezoelectric output peaks of current, voltage, and maximum power are dramatically increased, as compared with the pristine MoS₂.     

Polar‐Molecule‐Dominated Electrorheological Fluids Featuring High Yield Stresses

Recent works on the development of various electrorheological (ER) fluids composed of TiO₂, Sr? Ti? O, and Ca? Ti? O particles coated with C? O/H? O polar groups are summarized, in which an extremely large yield stress up to 200 kPa is measured and the dynamical yield stress reaches 117 kPa at a shear rate of 775 s^?1. Moreover, unlike that of traditional dielectric ER fluids, the yield stress displays a linear dependence on electric field strength. Experimental results reveal that it is the polar molecules adsorbed onto the dielectric particles that play the decisive role: the polar‐molecule‐dominated ER effect arises from the alignment of polar molecules by the enhanced local electric field in the gap between neighboring particles. The pretreatment of electrodes and the contrivance of new measuring procedures, which are desirable for the characterization and practical implementation of this material, are also discussed. The successful synthesis of these fluids has made many of the long since conceived applications of the ER effect available.     

Realization of High Performance AR‐coatings with Dust‐ and Water‐Repellent Properties

Hydrophobic coatings enable the manufacture of easy‐to‐clean surfaces having dust‐ and water‐repellent properties. In this work, a hydrophobic coating is deposited as a top layer on an antireflective (AR) multilayer system to produce low reflectance optical surfaces at a normal incident angle in the visible spectrum with dust‐ and water‐repellent properties for applications in precision optics. It is shown that the hydrophobic coating can be considered, from an optical point of view, as two adjacent thin layers having specific thicknesses and densities. In fact, the hydrophobic layer is one monolayer comprising molecular chains with anchoring groups responsible for the chemical bond with the substrate material and functional groups responsible for the water‐ and oil‐repellent properties. Their optical constants are determined and included in the final coating design. High performance AR coatings having an average reflectance of 0.14% at 7° incident angle in the 400‐680nm spectral range together with a pleasing purplered reflex color are produced. Coated lenses exhibit an excellent abrasion resistance, environmental stability, resistance to cleaning agents, homogeneity and water repellence with contact angles against water higher than 110°.     

Nanoporous Al‐Ni‐Co‐Ir‐Mo High‐Entropy Alloy for Record‐High Water Splitting Activity in Acidic Environments

Ir‐based binary and ternary alloys are effective catalysts for the electrochemical oxygen evolution reaction (OER) in acidic solutions. Nevertheless, decreasing the Ir content to less than 50 at% while maintaining or even enhancing the overall electrocatalytic activity and durability remains a grand challenge. Herein, by dealloying predesigned Al‐based precursor alloys, it is possible to controllably incorporate Ir with another four metal elements into one single nanostructured phase with merely ≈20 at% Ir. The obtained nanoporous quinary alloys, i.e., nanoporous high‐entropy alloys (np‐HEAs) provide infinite possibilities for tuning alloy's electronic properties and maximizing catalytic activities owing to the endless element combinations. Particularly, a record‐high OER activity is found for a quinary AlNiCoIrMo np‐HEA. Forming HEAs also greatly enhances the structural and catalytic durability regardless of the alloy compositions. With the advantages of low Ir loading and high activity, these np‐HEA catalysts are very promising and suitable for activity tailoring/maximization.     

High Detectivity Graphene‐Silicon Heterojunction Photodetector

A graphene/n‐type silicon (n‐Si) heterojunction has been demonstrated to exhibit strong rectifying behavior and high photoresponsivity, which can be utilized for the development of high‐performance photodetectors. However, graphene/n‐Si heterojunction photodetectors reported previously suffer from relatively low specific detectivity due to large dark current. Here, by introducing a thin interfacial oxide layer, the dark current of graphene/n‐Si heterojunction has been reduced by two orders of magnitude at zero bias. At room temperature, the graphene/n‐Si photodetector with interfacial oxide exhibits a specific detectivity up to 5.77 × 10¹³ cm Hz^1/2 W^‐1 at the peak wavelength of 890 nm in vacuum, which is highest reported detectivity at room temperature for planar graphene/Si heterojunction photodetectors. In addition, the improved graphene/n‐Si heterojunction photodetectors possess high responsivity of 0.73 A W^?1 and high photo‐to‐dark current ratio of ≈10⁷. The current noise spectral density of the graphene/n‐Si photodetector has been characterized under ambient and vacuum conditions, which shows that the dark current can be further suppressed in vacuum. These results demonstrate that graphene/Si heterojunction with interfacial oxide is promising for the development of high detectivity photodetectors.