Xiaowei Lei

Tilted washboard potentials, realized through acoustic, electric, or optical fields, provide a minimal model for driven transport in periodic energy landscapes. In this work, we develop a unified analytical framework describing particle dynamics in potentials inclined at arbitrary angles to an external flow. The system exhibits a well-defined transition between drift and locked regimes, governed by the ratio of potential to viscous drag forces. In the drift mode, the particle trajectory exhibits an intrinsically nonlinear oscillation with a finite mean slope, while the locked mode yields a straight trajectory along the externally applied potential node. The theory quantitatively reproduces previously reported experiments and establishes universal scaling for the drift-lock transition and particle separation. The universal scaling statement is understood within the stated dilute, overdamped, local-flow model. The exact phase analysis and the added validity criteria below specify where this interpretation applies. This work not only deepens the theoretical understanding of particle transport but also offers a framework for optimizing flow-based microsystem designs under low potential intensities and variable flow conditions.

Nanofluidic energy absorption systems store or dissipate mechanical work through pressure-driven intrusion and extrusion of a non-wetting liquid in a porous network. Their macroscopic pressure-volume response is strongly rate dependent, whereas the frequency dependence of the loop area and the associated energy metrics are often discussed separately from the underlying interface dynamics. Here we introduce a phenomenological constitutive model for the pressure-volume relationship by solving the first-order law under alternating pressure cycles. The model generates rate-dependent pressure-volume loops, a finite-memory window, and the associated input, dissipated, and recoverable work. The formulation provides a compact bridge between nanofluidic transport measurements and engineering-level energy metrics, while its single-time-scale assumptions define clear boundaries for application to cascade filling, pore-size heterogeneity, irreversible collapse, and inertial high-rate flow.

Electrowetting has emerged as a versatile technique for manipulating discrete liquid volumes. However, its practical utility is constrained by the saturation of the contact angle at elevated applied voltages, where further increases in voltage produce diminishing changes in wettability. In this work, we formulate a bounded statistical-mechanical description of the interfacial dipoles under an externally applied electric field. The resulting model recovers the classical quadratic voltage dependence in the low-field limit, while in the high-field limit the apparent contact angle saturates to a constant value. The probabilistic modulation also accounts for the asymmetry in electrowetting under positive and negative bias when the solid surface and the liquid possess unbalanced acid–base character. This work provides a self-consistent and experimentally falsifiable electrowetting framework, offering both a molecular-level interpretive tool for existing data and a predictive approach to rational design in digital microfluidic platforms.

Monte Carlo simulations combined with the embedded-atom method were employed to calculate the liquid surface tension, viscosity, and diffusion coefficients of fifteen lanthanide elements near their melting points in this work. Results indicate that the surface tension of liquid lanthanide metals not only decreases linearly with increasing temperature, but also varies with atomic number in a classical “double-valley” pattern. The calculated values show good agreement with available experimental data. Viscosity decreases exponentially with increasing temperature, whereas diffusion coefficients increase with temperature and exhibit an approximately exponential dependence, consistent with the Sutherland–Einstein equation. Further analysis shows the variation trends of these thermophysical properties with the atomic number, which are closely related to the electron configuration of lanthanide metals.

The addition of Cu or La plays an important role in microstructure and property manipulation of 4xxx series Al-Si alloys. However, the effects of Cu-La hybrid modification on the microstructure and properties of Al-5Si alloys and welding performance remain unclear. In this paper, the influence of Cu-La addition on the strength and elongation of one commercial Al-5Si alloy and the welding joint characterization are investigated. The results show that the addition of Cu-La can refine α-(Al) and Fe-rich phase and improve the fluidity. Meanwhile, the elongation can be improved by Cu-La microalloying, which is beneficial for the manufacturing filler wire. The uniform distribution of Cu in the alloy but not segregation at grain boundaries due to La addition is the key factor to adjust the mechanical properties. Moreover, the filler materials were used to conduct metal inert gas welding on 6061 alloy. It reveals that, with Cu-La addition, the weld pool width increases and porosity defect decreases significantly. This is ascribed to Cu-La co-addition enhancing wettability and fluidity, which improves the welding performance. Our results offer an effective strategy for manufacturing and optimizing welding performance of welding wires.