Channel Emulsification

T. Kawakatsu, Y. Kikuchi, and M. Nakajima Regular-Sized Cell Creation in Micro-Channel Emulsification by Visual Microprocessing Method. JAOCS 74, 317 (1997). 

Micro-channel emulsification is even farther away from industrial application however, there are a few small companies offering nozzle plates that show relatively large fluxes, coming into the realm of practical feasibility. For example, fluxes of... 

A second, new class of processes is that of membrane and micro-channel emulsification. A to-be-dispersed phase is here pushed through pores of a membrane or through micro-engineered micron-scale channels. At the pore or channel mouth, droplets are formed. These droplets can spontaneously detach from the pore or channel mouth (interfacial tension driven snap-off), due to the distortion of the droplet shape when it is still attached to the mouth. At higher fluxes or with channel mouths not giving a strong shape distortion, droplets are sheared off by a cross-flowing continuous phase. 

Alginate microspheres have been extensively used as delivery system because they are very easy to prepare, the process is very mild, and virtually any ingredient can be encapsulated (Vladisavljevic and Williams, 2005). That is the reason why they are chosen to exemplify the use of the membrane and channel emulsification processes to produce gel particles. 

Kobayashi I, Lou XF, Mukataka S, Nakajima M. 2005c. Preparation of monodisperse water-in-oil-m-water emulsions using microfluidization and straight-through micro-channel emulsification. J Am Oil Chem Soc 82 65-71. 

Sugiura S, Nakajima M, Yamamoto K, Iwamoto S, Oda T, Satake M, Seki M. 2004a. Preparation characteristics of water-in-oil-in-water multiple emulsions using micro-channel emulsification. J Colloid Interface Sci 270 221-228. 

S. Sugiura, M. Nakajima, and M. Seki Effect of Channel Structure on MicroChannel Emulsification. Langmuir 18, 5708 (2002). 

Jurkat cells have been lysed in a flow stream in a glass microchip for cell content analysis. After cell lysis, the two preloaded fluorescent dyes and their metabolites were released from the cells and separated by CE (see Figure 8.36). To prevent cell adhesion, the glass channel surface was modified by adsorbing Pluronic F-127 to the channels. In addition, to avoid blockage of adhered cell debris and to improve migration time stability, an emulsification agent, such as Pluronic P84, was added to the separation buffer [1176],... 

An emerging class of emulsification methods is not based on imposing an overall flow field, but rather by making individual droplets on the mouths of membrane pores or micro-engineered channels. Characteristic is that the flow fields applied are much milder energy consumption is much lower, while the droplet sizes are strongly dependent on the shape and dimensions of the pores or micro-channels. A number of processes belong to this class ... 

Figure 15.17. (a) Emulsification process found by Kawakatsu et al. (2001a). Oil was led through a small channel, which ended on a slit-shaped opening (Van Dijke et al. 2006). (b) A... 

For the caustic systems used for recovering heavy oils it has been observed that the formation of stable emulsions by spontaneous emulsification is desirable (10, 11). The stable emulsions formed during caustic flooding tend to lower injected water mobility, viscous fingering, and water channeling while improving the sweep efficiency of the injected fluids. The produced fluids from this recovery technique are emulsions and must be demulsi-fied. 

In the first demonstration of formation of monodisperse droplets in a microfluidic T-junction [9], on the basis of the experimental results on scaling of the droplet size with the rate of flow of the continuous fluid, it was hypothesized that the droplets are sheared off from the junction by the flow of the continuous fluid, similarly to the classical models of shear-driven emulsification. However, the fact that the break-up occurs in a confined geometry of the microchannels, and that the droplet growing off the inlet of the fluid-to-be-dispersed usually occupies a significant fraction of the cross-section of the main channel, suggest that the pressure drop along a growing droplet may be an important factor in the process. 

This chapter overviews ongoing activities in microchannel process technology development, from single-channel laboratory experiments to industrially-driven, multi-channel and multi-unit development at or near the prototype and pilot level. The non-reactive unit operations covered include heat transfer, mixing, emulsification, phase separation, phase transfer, biological processes, and body force applications. 

Sugiura S, Nakajima M, Seki M (2002) Effect of channel structure on microchannel emulsification. Langmuir 18(15) 5708-5712... 

The T-shaped junction is the most studied shear-based emulsification device. In T-shaped junctions as shown in Fig. 4, the continuous phase flows through the horizontal channel, and the to-be-dispersed phase is pressurized through the vertical channel where it meets the continuous phase, is distorted, and eventually forms droplets at the T-junction. Typical images of this process in an experimental setup through Lattice Boltzmann simulations are shown in Fig. 4. 

S. Sugiura, M. Nakajima, M. Seki, Effect of channel structure on microchaimel emulsification. Langmuir. 2002, 18. 5708-5712. 

Figure18.7 Top Left schematic drawing of the MFFD. Top right optical images of MAOP-DMS emulsification with methylene blue dye labeled water in an MFFD made of PU (a, b) or PDMS (c, d) MAOP-DMS was delivered to the central channel (a, d) or the side channels (b, c). Bottom SEM images of poly(TPCDA) particles (a, b, c) and poly(PETA-3) particles (d) obtained with 2 (a),4 (b, d) and 6wt.% (c) of initiator (HCPK). From Ref [12].

In this chapter, we describe the new technologies that can produce various double emulsions of controlled sizes, structures and compositions. We also explain the emerging new applications of the monodisperse double emulsions prepared using those technologies. Section 21.2 describes the use of porous materials for emulsification membranes. Section 21.3 describes the use of a channel array or through-holes fabricated on a silicon substrate. Section 21.4 describes the use of microfiuidic channels on a planar substrate. Section 21.5 explains coaxial microcapillary devices. Section 21.6 describes the applications of monodisperse multiple emulsions to a new class of functional materials. 

Microcharmel (MC) emulsification [52-58] is a technique developed in the 1990s, which utilizes hthographically fabricated geometries for producing monodisperse emulsion droplets. Thus far, two configurations have mainly been studied one consists of a micron-sized comb-hke channel array microfabricated on a silicon plate [52-54], whereas the other is called a straight-through MC plate and has thousands of... 

---