Engineering Disorder in Droplet Packings through Polydispersity and Adhesion.

Disorder opens avenues for biomimetic design and material innovation if harnessed as a tunable property. A robust microfluidic platform is presented that transforms disorder into a controllable design parameter in droplet-based soft matter systems. This work is inspired by extensive research on controlled disorder in 2D materials and adapts it to 2D microdroplet packings. Controlled disorder is investigated through a microfluidic platform integrating droplet generation, transfer, and imaging. Transfer channel height optimization and air interface sweeping, the two microfluidic engineering strategies, aided in compact and reproducible 2D droplet packing. Adhesion and polydispersity are modulated to engineer a controlled disorder in droplet packing. Structural disorder is quantified using metrics derived from statistical mechanics, such as bond orientational order parameters and excess entropy. Bond orientational parameters validate the increase in disorder as the polydispersity increases. Additionally, excess entropy reveals that adhesive droplets exhibit higher structural disorder than nonadhesive droplets. Together, these structural parameters demonstrate the platform's capability to engineer controlled disorder. This workflow establishes a microscale 2D platform for exploring controlled disorder in patterned materials and biomimetic models.