A nano emulsion generator using a microchannel and a bolt blamped type transducer

Emulsification mechanism in an ultrasonic microreactor: Influence of surface roughness and ultrasound frequency

“…10 and Vid 12 . Previous accounts of emulsification at a frequency above 1 MHz point to the role of a standing wave in the microchannel in the breakup of dispersed phase droplets [29] , [30] . To determine the presence of a standing wave in the microchannel, we introduced 10 μm fluorescent polystyrene particles in the channel.…”

“…The bubble oscillation in the aqueous phase leads to the generation of oil droplets in water. High-frequency ultrasound (f > 1 MHz) has also been successfully applied for emulsification in batch and microreactors [27] , [28] , [29] , [30] . For this frequency range, the droplet breakup results from the surface destabilization of the interface in the absence of any cavitation activity.…”

Ultrasound-assisted production and optimization of mini-emulsions in a microfluidic chip in continuous-flow

“…The height (175 µm) and width (290 µm) of the serpentine microreactor were chosen to be considered a microfluidic channel (i.e. < 1000 µm) and they are within the range of reported microchannels in which cavitation has been observed (20–1000 µm height, 100–1000 µm width) [21] , [22] , [23] , [24] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] , [33] , [34] , [35] , [36] , [37] . For the channel length (7.0 cm), an intermediate value was chosen within reported values (1.2–28 cm).…”

“…PDMS would not be the most suitable material for this purpose, as it will deform with higher flow rates and could be swollen by some organic solvents [42] . Suitable materials to construct, for example, several identical units in parallel [24] , [65] are silicon–glass [65] or engraved metal [33] , [34] , [35] , [36] , [37] , in which impedance differences are minimized [66] and which are capable of withstanding higher pressures employed for emulsion production on a L/h scale. Another alternative would be the use of sonoreactor bags [40] .…”

“…In microfluidic channels the use of low-frequency ultrasound generates cavitation bubbles [21] , [22] , [23] , [24] , [25] , which have been used for DNA fragmentation [26] , cell disruption [27] , [28] , generation of chemi- and sonoluminescence [29] , mixing of low and high-viscosity fluids [30] , [31] , dissolution of gas bubbles in water [32] and liquid–liquid extraction process [33] , [34] . The demonstration of emulsion preparation using ultrasound in microfluidic devices has been described in conference proceedings [35] , [36] , [37] , and in two research articles some of the mechanism of octane and water emulsification have been reported [33] , [34] . Different small-scale reactors with sonication have been explored for preparing mini-emulsions and the size and polydispersity of the emulsion droplets have been measured: a glass flow-through cell with a 2.0 mm inner diameter [38] , epoxy resin channels with a 1.0 – 1.5 mm in diameter [39] and an ultrasonic bag reactor with microstructures inside which can be considered as a scaled-up microfluidic sonoreactor [40] .…”