Droplet group production in an AC electro-flow-focusing microdevice

Abstract

We report the production of droplet groups with a controlled number of drops in a microfluidic electro-flow focusing device under the action of an AC electric field. This regime appears for moderate voltages (500-700 V peak-to-peak) and signal frequencies between 25 and 100 Hz, much smaller than the droplet production rate (∼ 500 Hz). For this experimental conditions the production frequency of a droplet package is twice the signal frequency. Since the continuous phase flow in the microchannel is a Hagen-Poiseuille flow, the smaller droplets of a group move faster than the bigger ones leading to droplet clustering downstream.

Rectifying jet breakup by electric forcing

“…The jet breaks up into one big and a train of smaller droplets, as can be seen in Figure 4d at f pert = 1 kHz. This regime corresponds to observations of the production of groups of droplets under the influence of the electric field in the dripping regime 40 . A second increase of a p is seen around 8 kHz, the natural production frequency of the jet, where a 0 decreases.…”

“…This regime corresponds to observations of the production of groups of droplets under the influence of the electric field in the dripping regime. 40 A second increase of a p is seen around 8 kHz, the natural production frequency of the jet, where a 0 decreases. This means that when f pert is around the natural breakup frequency of the jet, it is amplified, while the other frequencies in the spectrum are reduced.…”

Pushing the limits of microfluidic droplet production efficiency: engineering microchannels with seamlessly implemented 3D inverse colloidal crystals

“…Despite their ability to control droplet size, droplet generation processes using a single microchannel confluence usually suffer from the critical limitation of low production throughput. The number-base droplet production speed depends on the type of droplet generation scheme (e.g., squeezing, dripping, and jetting), but most droplet generation frequencies using a flow-focusing scheme or T-junction are on the order of several hundred Hz, 17,[27][28][29][30][31][32] and only a limited number of systems are able to produce microdroplets at high frequency. 33 Consequently, applications for particulate preparation that use droplets as templates require long-term operations to ensure sufficient productivity.…”

Controllable production of Janus ligaments by AC fields in a flow-focusing junction

“…AC electro-flow focusing devices have been previously used to control the production of droplets (Tan et al, 2014;Castro-Hernández et al, 2017) and long jets (Castro-Hernández et al, 2015, 2016. Tan et al (2014) studied in depth the influence of the voltage amplitude, signal frequency and conductivity of the dispersed phase on the droplet size and production frequency.…”