Rationally Designed Li-Ag Alloy with In-Situ-Formed Solid Electrolyte Interphase for All-Solid-State Lithium Batteries.

All-solid-state lithium batteries (ASSLBs) with sulfide-based solid electrolytes have attracted significant attention as promising energy storage devices, owing to their high energy density and enhanced safety. However, the combination of a lithium metal anode and a sulfide solid electrolyte results in performance degradation, owing to lithium dendrite growth and the side reactions of lithium metal with the solid electrolyte. To address these issues, a Ag-based Li alloy with a favorable solid electrolyte interphase (SEI) was prepared using electrodeposition and applied to the ASSLB as an anode. The electrochemically formed SEI layer on the Li-Ag alloy primarily comprised LiF and Li2O with high mechanical strength and Li3N with high ionic conductivity, which suppressed the formation of lithium dendrites and short-circuiting of the cell. The symmetric cell with the Li-Ag alloy achieved a critical current density of 1.6 mA cm-2 and maintained stable cycling for over 2000 h at a current density of 0.6 mA cm-2. Consequently, the all-solid-state lithium cell assembled with the Li-Ag alloy anode with SEI, Li6PS5Cl solid electrolyte, and LiNi0.78Co0.10Mn0.12O2 cathode delivered a high discharge capacity of 185 mAh g-1 and exhibited good cycling performance in terms of cycling stability and rate capability at 25 °C.

Fabricating self-powered microfluidic devices via 3D printing for manipulating fluid flow.

Advances in 3D printing technologies allow fabrication of complex structures at micron resolution. Here, we describe two approaches of fabricating self-powered microfluidic devices utilizing 3D printing: PDMS (polydimethylsiloxane)-based microfluidic devices with a built-in vacuum pocket fabricated by soft lithography using a 3D-printed mold, and non-PDMS microfluidic devices operating by a removable vacuum battery fabricated by 3D-printed materials. These microfluidic devices can be used for controlling blood flow and separating blood plasma. For complete details on the use and execution of this protocol, please refer to Woo et al. (2021).

Molecular diffusion analysis of dynamic blood flow and plasma separation driven by self-powered microfluidic devices.

Integration of microfluidic devices with pressure-driven, self-powered fluid flow propulsion methods has provided a very effective solution for on-chip, droplet blood testing applications. However, precise understanding of the physical process governing fluid dynamics in polydimethylsiloxane (PDMS)-based microfluidic devices remains unclear. Here, we propose a pressure-driven diffusion model using Fick's law and the ideal gas law, the results of which agree well with the experimental fluid dynamics observed in our vacuum pocket-assisted, self-powered microfluidic devices. Notably, this model enables us to precisely tune the flow rate by adjusting two geometrical parameters of the vacuum pocket. By linking the self-powered fluid flow propulsion method to the sedimentation, we also show that direct plasma separation from a drop of whole blood can be achieved using only a simple construction without the need for external power sources, connectors, or a complex operational procedure. Finally, the potential of the vacuum pocket, along with a removable vacuum battery to be integrated with non-PDMS microfluidic devices to drive and control the fluid flow, is demonstrated.

Different Single-Enzyme Conformational Dynamics upon Binding Hydrolyzable or Nonhydrolyzable Ligands.

Single-molecule measurements of protein dynamics help unveil the complex conformational changes and transitions that occur during ligand binding and catalytic processes. Using high-resolution single-molecule nanocircuit techniques, we have investigated differences in the conformational dynamics and transitions of lysozyme interacting with three ligands: peptidoglycan substrate, substrate-based chitin analogue, and indole derivative inhibitors. While processing peptidoglycan, lysozyme followed one of the two mechanistic pathways for the hydrolysis of the glycosidic bonds: a concerted mechanism inducing direct conformational changes from open to fully closed conformations or a nonconcerted mechanism involving transient pauses in intermediate conformations between the open and closed conformations. In the presence of either chitin or an indole inhibitor, lysozyme was unable to access the fully closed conformation where catalysis occurs. Instead, lysozymes' conformational closures terminated at slightly closed, "excited" conformations that were approximately one-quarter of the full hinge-bending range. With the indole inhibitor, lysozyme reached this excited conformation in a single step without any evidence of rate-liming intermediates, but the same conformational motions with chitin involved three hidden, intermediate processes and features similar to the nonconcerted peptidoglycan mechanism. The similarities suggest that these hidden processes involve attempts to accommodate imperfectly aligned polysaccharides in the active site. The results provide a detailed glimpse of the enzyme-ligand interplay at the crux of molecular recognition, enzyme specificity, and catalysis.

Selective Manipulation of Biomolecules with Insulator-Based Dielectrophoretic Tweezers.

Insulator-based dielectrophoretic (iDEP) trapping, separating, and concentrating nanoscale objects is carried out using a non-metal, unbiased, mobile tip acing as a tweezers. The spatial control and manipulation of fluorescently-labeled polystyrene particles and DNA were performed to demonstrate the feasibility of the iDEP tweezers. Frequency-dependent iDEP tweezers' strength and polarity were quantitatively determined using two theoretical approaches to DNA, which resulted in a factor of 2 ~ 40 differences between them. In either approach, the strength of iDEP was at least 4-order of magnitude stronger than the thermal force, indicating iDEP was a dominant force for trapping, holding, and separating DNA. The trapping strength and volume of the iDEP tweezers were also determined, which further supports direct capture and manipulation of DNA at the tip end.

Electronic structure and properties of lithium-rich complex oxides.

Lithium-rich complex transition-metal oxides Li2MoO3, Li2RuO3, Li3RuO4, Li3NbO4, Li5FeO4, Li5MnO4 and their derivatives are of interest for high-capacity battery electrodes. Here, we report a first-principles density-functional theory study of the atomic and electronic structure of these materials using the Heyd-Scuseria-Ernzerhof (HSE) screened hybrid functional which treats all orbitals in the materials on equal footing. Dimerization of the transition-metal ions is found to occur in layered Li2MoO3, in both fully lithiated and partially delithiated compounds. The Ru-Ru dimerization does not occur in fully lithiated Li2RuO3, in contrast to what is commonly believed; Ru-Ru dimers are, however, found to occur in the presence of neutral lithium vacancies caused by lithium loss during synthesis and/or lithium removal during use. We also analyze the electronic structure of the complex oxides and discuss the delithiation mechanism in these battery electrode materials.

Electronic structure, polaron formation, and functional properties in transition-metal tungstates.

Transition-metal tungstates MWO4 (M = Co, Ni, Cu, Zn) have applications in many areas, including supercapacitors. A good understanding of the electronic structure is essential to understanding their functional properties. Here, we report a first-principles study of the materials using hybrid density-functional calculations. The electronic structure is analyzed with a focus on the nature of the electronic states near the band edges. We find that hole polarons can form at the Co lattice site in CoWO4 and the O site in NiWO4, CuWO4, and ZnWO4, resulting in the formation of Co3+ in the former and O- in the latter. The electrochemical activity observed in certain tungstate compounds, but not in others, appears to be related to the ability to form hole polarons on the transition-metal ions. The formation energy and migration barrier of the hole polaron in CoWO4 are also calculated and the results are employed to understand the reported p-type conductivity.

Insights on the Structure, Molecular Weight and Activity of an Antibacterial Protein-Polymer Hybrid.

Protein-polymer conjugates are attractive biomaterials which combine the functions of both proteins and polymers. The bioactivity of these hybrid materials, however, is often reduced upon conjugation. It is important to determine and monitor the protein structure and active site availability in order to optimize the polymer composition, attachment point, and abundance. The challenges in probing these insights are the large size and high complexity in the conjugates. Herein, we overcome the challenges by combining electron paramagnetic resonance (EPR) spectroscopy and atomic force microscopy (AFM) and characterize the structure of antibacterial hybrids formed by polyethylene glycol (PEG) and an antibacterial protein. We discovered that the primary reasons for activity loss were PEG blocking the substrate access pathway and/or altering protein surface charges. Our data indicated that the polymers tended to stay away from the protein surface and form a coiled conformation. The structural insights are meaningful for and applicable to the rational design of future hybrids.