# Efficient Separation of Methanol Single-Micron Droplets by Tailing Phenomenon Using a PDMS Microfluidic Device

## TL;DR

A new microfluidic device efficiently separates methanol droplets using a tailing phenomenon without surfactants.

## Contribution

A novel surfactant-free method for generating and separating single-micron organic droplets using a PDMS microfluidic device.

## Key findings

- A tapered separation channel with side channels enhances shear forces to break up methanol droplets.
- Surface treatment with CYTOP fluoropolymer prevents organic fluid damage to PDMS devices.
- The method enables tailing-based separation of methanol droplets smaller than 5 μm in diameter.

## Abstract

Microdroplet-based fluidic systems have the advantages of small size, short diffusion time, and no cross-contamination; consequently, droplets often provide a fast and precise reaction environment as well as an analytical environment for individual molecules. In order to handle diverse reactions, we developed a method to create organic single-micron droplets (S-MDs) smaller than 5 μm in diameter dispersed in silicone oil without surfactant. The S-MD generation microflow device consists of a mother droplet (MoD) generator and a tapered separation channel featuring multiple side channels. The tapered channel enhanced the shear forces to form tails from the MoDs, causing them to break up. Surface treatment with the fluoropolymer CYTOP protected PDMS fluid devices from organic fluids. The tailing separation of methanol droplets was accomplished without the use of surfactants. The generation of tiny organic droplets may offer new insights into chemical separation and help study the scaling effects of various chemical reactions.