Programmable Particle Assembly in Composite Through Controlled Charge Injection

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 with 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 light-emitting diode (LED) packaging, wherein phosphor particles are controllably deposited on a
$1\times 1$
mm 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.