A novel surgery-like strategy for droplet coalescence in microchannels

Abstract

We report an innovative and efficient surgery-like strategy for achieving the coalescence of surfactant-stabilized droplets in microchannels. As pairs of preformed droplets flow across a micro-lancet, with a suitable surface wettability, in a converging microchannel simultaneously, their surfaces are scratched by the micro-lancet, which causes temporarily local scattering of surfactants, and thus induces their coalescence by joining up their scratched wounds. Our approach shows highly controllable flexibility and stability. We demonstrate this by controlling the coalescence of emulsion droplets with different numbers and complex structures. This surgery-like strategy is totally passive and has great potential in myriad applications including micro-reaction, high-throughput injection, and multiple emulsion formation, etc.

Droplet Micro‐Reactor for Internal Gelation to Fabricate ZrO2 Ceramic Microspheres

“…The dyed component was soon distributed inside the droplet under a proper flow rate ratio. Actually, the mixing was caused by the convection inside the drop, and the mechanism of this motion has already been studied by Deng and Stone . In this droplet micro‐reactor, the viscosity ratio and the flow rate ratio of the two components will affect the mixing efficiency, as found in our experiments.…”

From single-molecule detection to next-generation sequencing: microfluidic droplets for high-throughput nucleic acid analysis

“…Subsequent to their generation, droplets need to be manipulated in ways that mimic the standard analytical procedures used on the bench top. Fortunately, a wide range of (both passive and active) functional components have been presented for operations that include droplet merging (Niu et al 2008;Deng et al 2013;Mazutis and Griffiths 2012;Akartuna et al 2015), dilution (Niu et al 2011;Sun and Vanapalli 2013), dosing (Abate et al 2010;Chen et al 2008), splitting (Link et al 2004;Gao et al 2016), pairing (Ahn et al 2011;Bai et al 2010), sorting (Baret et al 2009;Nam et al 2012;Cao et al 2013), trapping/releasing Korczyk et al 2013;Courtney et al 2017), counting (Boybay et al 2013;Yesiloz et al 2015;) and incubation (Huebner et al 2009;Wen et al 2015). An instructive example in this respect was reported by Hatch et al (2011), who used successive bifurcations to split single droplets into 256 daughter droplets in a rapid and passive fashion ( Fig.…”

Droplet Coalescence by Selective Wettability Enhancement in Microfluidic Devices

“…Such techniques include electrocoalescence [6,7], dielectrophoresis (DEP) [8,9], magnetophoretically actuated droplet coalescence [10], and temperature and pneumatically actuated droplet coalescence [11][12][13]. While active techniques result in highly controlled droplet dynamics, they are inherently complex techniques requiring complicated methods for the fabrication of microfluidic channels with integrated elements to be activated by the external sources [14]. Moreover, the presence of external fields limits the use of the active techniques to specific compatible systems.…”

“…Recent studies of geometrically induced coalescence included inducing droplet coalescence in the merging zone of Y-and T-junction channels [15,16], and by introducing microgrooves [16], micropillars [17], micro-lancet [14], and by microexpansion techniques [18], and microfluidic traps [19]. These techniques are restricted to the design of the channels and require accurate droplet synchronization [3].…”