Microdroplet formation of water and nanofluids in heat-induced microfluidic T-junction

Abstract

This paper reports experimental investigations on the droplet formation and size manipulation of deionized water (DIW) and nanofluids in a microfluidic Tjunction at different temperatures. Investigations of the effect of microchannel depths on the droplet formation process showed that the smaller the depth of the channel the larger the increase of droplet size with temperature. Sample nanofluids were prepared by dispersing 0.1 volume percentage of titanium dioxide (TiO 2 ) nanoparticles of 15 nm and 10 nm 9 40 nm in DIW for their droplet formation experiments. The heater temperature also affects the droplet formation process. Present results demonstrate that nanofluids exhibit different characteristics in droplet formation with the temperature. Addition of sphericalshaped TiO 2 (15 nm) nanoparticles in DIW results in much smaller droplet size compared to the cylindrical-shaped TiO 2 (10 nm 9 40 nm) nanoparticles. Besides changing the interfacial properties of based fluid, nanoparticles can influence the droplet formation of nanofluids by introducing interfacial slip at the interface. Other than nanofluid with cylindrical-shaped nanoparticles, the droplet size was found to increase with increasing temperature.

Micro-magnetofluidics: interactions between magnetism and fluid flow on the microscale

“…Since ferrofluid is a special class of nanofluid, even without an applied magnetic field, the droplet formation of ferrofluid is affected by the nanoparticles and their surfactant. Nanoparticles at the fluid interface reduce the interfacial tension leading to the formation of smaller droplets as compared to those of the pure carrier fluid under the same condition (Murshed et al 2009). Chen et al (2009) only used the magnetic body force to form ferrofluid droplets through an orifice.…”

Characterization of acoustic droplet formation in a microfluidic flow-focusing device

“…Several groups of researchers have attempted to provide local control together with the flow-rate ratio ϕ upon extending the droplet size distribution [14][15][16][17][18][19][20][21]. Kim et al [14] and He et al [15] attempted to use an electric field in a flowfocusing microfluidic device to transform the flow front of the dispersed phase to a Taylor cone, which causes the droplet to break up due to the Rayleigh capillary instability.…”

“…Submicron-sized droplets can be formed with this method, but the droplet size can only be controlled precisely at small flow-rate ratios. Nguyen et al [16], Murshed et al [17], and Tan et al [18] developed thermally controlled droplet formation in flow-focusing and T-shaped geometries. This method exploits the temperature-dependent nature of viscosity and interfacial tension to affect the breakup of droplets under preset temperatures.…”

Industrial lab-on-a-chip: Design, applications and scale-up for drug discovery and delivery

“…The active control of the 2 droplet size can be achieved using controllable moving wall structures [11], integrated 3 microheaters [119] (Fig. 3.1.1d), and pneumatically [120,121] X-and Y-junction.…”

“…Fabrication of straight-through channels by photolithography and Deep Reactive ion Etching (DRIE) adapted from [44] (for clarity purpose, the thickness of the silicon substrate is unrealistically small compared to the thickness of deposited layers); (c) Fabrication of micronozzles by photolithography and two-step DRIE [63,68]. (d) Active T-junction with controllable moving wall structure [120] and integrated microheater [119]; (e) Cross junction [45]; (f) Y-junction [127]; (g) co-flow [135,164,165]; (h) Standard flow focusing device [141]; (i) Flow focusing device with CP supplied through the central channel [166]; (j) Flow focusing with counter-current flow [82]; (k) Cross flow [150]; (i) Spontaneous droplet generation [133,134]. In all figures, DP does not wet the channel walls.…”