Ji Zeng

The rapid development of electric vehicles has increased the demand for high-efficiency thermal management through topology-optimized cold plates. However, the underlying physical basis of this effectiveness under varying operating conditions remains unclear. This study investigated the thermal-hydraulic behavior of confined battery liquid cooling plates using topology optimization with Reynolds number (Re), coolant composition, heat source intensity, and thermal-hydraulic weighting ratio as operating inputs. The optimized cold plate consistently formed a hierarchical transport structure composed of a main flow pathway and distributed branches, and stronger thermal loading produced more local branches around the main flow pathway. Standardized sensitivity analysis revealed that different operating inputs acted through distinct physical routes. Heat removal was jointly governed by coolant properties, Re, and objective weighting, whereas viscous dissipation was governed mainly by coolant composition and Re. Compared with the serpentine and rectangular fixed channel reference configurations, this hierarchical transport structure reduced temperature nonuniformity by 28% and 70%, respectively. Field synergy analysis interpreted the matching between the velocity field and the temperature gradient field after morphology evolution. Field synergy number (Fc) increased by about 3.1 times, and flow energy consumption was reduced by about 85% relative to the serpentine configuration. The higher Fc and lower flow energy consumption indicate that the cooling improvement comes from the main flow and branch transport mode, which produces more favorable synergy between the velocity field and the temperature gradient field. This study provides a physical interpretation of channel morphology evolution in topology-optimized cold plates for battery thermal management.

Composite materials with precisely controlled particle assembly show exciting properties and enable numerous new applications. However, it is challenging to manipulate particle patterns in a programming mean during composite fabrication. In this study, we propose a novel electric-field-based method for particle assembly. In such a method, charges generated in air by corona discharge are injected into the liquid polymer and attached to particles, and charged particles are directionally driven by the electric field to form assembled patterns. Compared to the conventional electric-field-based particle assembly methods, the presented method eliminates the requirement of the particle’s electric properties, thus extending the potential applications. Moreover, enhancing particle charge amount can lead to high-efficiency particle assembly. By controlling the charge injection area with masks or tuning the electric field with the patterned electrodes, programmable particle assembly is achieved in a low-cost way. As a demonstration of the application, the proposed method is implemented in LED packaging, wherein phosphor particles are controllably deposited on a 1mm × 1mm LED chip in the silicone gel, which achieves directional sedimentation. The optical performances are enhanced significantly, especially in angle color uniformity (ACU) and luminous efficiency. Furthermore, this new charge-injection-based particle assembly method shows broad application prospects in large-scale composite manufacture and high-precision electronic device packaging.

The electric field is considered an effective stimulus to control droplet bounce or adhesion on demand on solid surfaces, which is important for various applications, including water harvesting and oil/water separation. However, it remains challenging to switch droplet bouncing/adhering on electrode surfaces smartly. Herein, we present a smart control method for droplet bouncing on dielectric surfaces by coupling charge transfer with contact electrification and a uniform electric field. Subject to electric fields, water droplets carrying the like charges in the insulating silicone oil present electric field-direction-dependent impact behaviors, bifurcating into bouncing and adhesion on hydrophobic and hydrophilic surfaces. Furthermore, oppositely charged water droplets with contact electrification led to contrary bouncing behaviors on hydrophobic and hydrophilic surfaces. The transfer charges and electric forces in the experiments are especially quantitively analyzed. By constructing dielectric pairs with hydrophobic and hydrophilic surfaces, reciprocating bouncing or selective adhesion can be modulated via switching electric field directions. This route of separately charging droplets and building electric fields facilitates droplet manipulation techniques and applications.