Efficient Generation of Microdroplets Using Tail Breakup Induced with Multi-Branch Channels

Abstract

In recent years, research on the application of microdroplets in the fields of biotechnology and chemistry has made remarkable progress, but the technology for the stable generation of single-micrometer-scale microdroplets has not yet been established. In this paper, we developed an efficient and stable single-micrometer-scale droplet generation device based on the fragmentation of droplet tails, called “tail thread mode”, that appears under moderate flow conditions. This method can efficiently encapsulate microbeads that mimic cells and chemical products in passively generated single-micrometer-scale microdroplets. The device has a simple 2D structure; a T-junction is used for droplet generation; and in the downstream, multi-branch channels are designed for droplet deformation into the tail. Several 1–2 µm droplets were successfully produced by the tail’s fragmentation; this continuous splitting was induced by the branch channels. We examined a wide range of experimental conditions and found the optimal flow rate condition can be reduced to one-tenth compared to the conventional tip-streaming method. A mold was fabricated by simple soft lithography, and a polydimethylsiloxane (PDMS) device was fabricated using the mold. Based on the 15 patterns of experimental conditions and the results, the key factors for the generation of microdroplets in this device were examined. In the most efficient condition, 61.1% of the total droplets generated were smaller than 2 μm.

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

“…The device consists of two components: a mother droplet (MoD) generator and a single-micron droplet (S-MD) separator. The basic structure of the fluidic device is an adaptation of the device design we developed in 2021 [31] for methanol.…”

“…Droplet separation and recovery devices mainly utilize multilayer flow extraction and separation to isolate the target products [30]. So far, we have succeeded in generating singlemicron droplets from approximately 100 µm droplets using water and oil by applying the tailing phenomenon [31]. Most experiments to date have been conducted on an aqueous phase dispersed in an oil phase.…”