Under-liquid Self-Assembly of Submerged Buoyant Polymer Particles

TL;DR

This paper investigates the self-assembly of plasma-treated polyethylene beads submerged in liquid, revealing how capillary forces and surface energy modifications lead to ordered structures and defect healing through vibration.

Contribution

It introduces a novel method for submerged self-assembly of buoyant polymer particles using plasma treatment and capillary forces, demonstrating defect healing via mechanical vibration.

Findings

Formation of well-ordered 2D quasi-crystalline structures

Capillary immersion attraction drives self-assembly

Mechanical vibration heals point defects

Abstract

The self-assembly of submerged cold-plasma-treated polyethylene beads is reported. The plasma-treated immersed millimetrically-sized polyethylene beads formed well-ordered 2D quasi-crystalline structures. The submerged floating of light polyethylene beads is possible due to the energy gain achieved by the wetting of the high-energy plasma-treated polymer surface prevailing over the energy loss due to the upward climb of the liquid over the beads. The capillary immersion attraction force is responsible for the observed self-assembly. The observed 2D quasi-crystalline structures demonstrate dislocations and point defects. Mechanical vibration of self-assembled rafts built of polyethylene beads leads to the healing of point defects. The immersion capillary lateral force governs the self-assembly, whereas the elastic force is responsible for the repulsion of polymer beads.