Microcapillary devices

Utada AS, Lorenceau E, Link DR, Kaplan PD, Stone HA, Weitz DA (2005) Monodisperse double emulsions generated from a microcapillary device. Science 308 537-541... 

The formation of polymersomes from water in- oil-in-water drops. Initially, a double emulsion consisting of single aqueous drops within drops of a volatile organic solvent ( oil ) is prepared using a microcapillary device. Amphiphilic diblock copolymers dissolved in the middle phase assemble into monolayers at the oil-water interfaces. Evaporation of the solvent then leads to the formation of polymer bilayers (polymersomes). 

FIGURE 20.13 Examples of multiple emulsions formed in microfluidic systems (a) multiple shells-multiple cores configurations of monodisperse triple emulsions made with cascaded microcapillary devices results. (Reproduced with permission from Utada, A.S. et al.. Bull. MRS, 32(09), 702, 2007.), (b) composite emulsion formed by droplets of different composition and different volumes. (Reproduced with permission from Hashimoto, M. et al.. Small, 3(10), 1792, 2007.), and (c) examples of anisotropic particles formed by either polymerization (spheres and disks, rods) of droplets of monomer or thermal setting of droplets. (Reproduced with permission from Xu, S. et al., Angew. Chem. Int. Ed. Engl, 44(5), 724, 2005.)... 

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. 

Figure 21.8 A microcapillary device for generating monodisperse doubleemulsion, (a) A schematic ofthe device and flow orientation (b) formation of monodisperse O/W/O emulsion consisting of uniform waterdroplets having a single silicone oil droplet. CV is less than 1%. From Ref [99]. Reprinted with permission from AAAS.

Figure 6.14 Microcapillary devices for generating monodisperse emulsions from coaxial liquid jets. This approach allows single-, double-, or triple emulsion droplets to be generated in a single step (Weitz).

A. Berthold, F. Laugere, H. Schellevis, C.R. de Boer, M. Laros, R.M. Guijt, P.M. Sarro and M.J. Vellekoop, Fabrication of a glass-implemented microcapillary electrophoresis device with integrated contactless conductivity detection, Electrophoresis, 23 (2002) 3511-3519. 

A micromixer in which the fluid can be stirred by periodically pumping through the side channels is shown in Figure 3.45 [481]. The periodic perturbation applied via the side channel allows liquids A and B to be mixed. Other mixers based on oscillating pressure-pumped flow have also been reported [482,483]. Two droplets (600 pL) were merged and mixed by a push-pull (shuttling) method in a PDMS device consisting of a hydrophobic microcapillary vent (HMCV) [364]. 

Figure 10.13 shows examples of high-resolution patterns formed on small scale cylindrical objects - optical fiber and microcapillary tubes [1]. These simple devices (integrated photomasks for optical fiber Bragg gratings and intravascular stents), require only one patterned layer. 

Cf-FAB in all its forms is a low flow-rate technique, i.e., 1-15 pl/min. Therefore, one should use either a microbore or packed microcapillary column, or a conventional colunm in combination with a post-column splitting device [47-48]. 

A 5-20-pm-lD micro-ESl needle was described by Eimnett and Caprioli [70]. The flow-rates used were 0.3-6.4 pEmin. Similar needles were successfully made by other as well. Robins and Guido [71] reported an integrated packed 150-250-pm-lD microcapillary LC coluitm-micro-ESl device. A Teflon frit retains the coluttm packing material. The last part of the fused-silica colirnm tubing is drawn into a sharp tip to act as an ESI emitter. 

The bottom-up approach very much resembles classical protein identification strategies. The proteins in the proteome are first separated by 2D-GE (Ch. 17.3), or in some cases by SCX, size-exclusion (SEC), or affinity (AfC) chromatography. Specific proteins are excised from the gel, blotted, or electroeluted. The protein is digested, and the digest is analysed by LC-MS. The EC separation involves either RPLC with microcapillary or nano-LC columns (Ch. 17.5.2), or 2D-LC with typically SEC or SCX in the first dimension and RPLC in the second (Ch. 17.5.4). Alternatively, the sample may be introduced via either direct-infusion nano-ESl (Ch. 17.2), CE-MS (Ch. 17.5.6), or a microfluidic device coupled to MS (Ch. 17.5.5). 

The universal TLC facilities are utilized plates, adsorbents, microcapillaries, or micropipettes for sample application, development tanks, detection spray reagents, devices for spraying, and densitometers for quantification. Plates are either commercially precoated or handmade. Silica gel G (G, for gypsum as a binding substance), silica gel H (no binding substance) and, rarely, alumina and kieselguhr, form the thin-layer stationary phases. Complete sets of devices necessary for the preparation of handmade plates are commercially available. After the silica gel slurry is spread on the plates, they are left to dry in the air for at least 24 hr and shortly in an oven at 110°C. The plates are then ready for either direct use or for modification of the layer. From the great variety of precoated plates, which are commercially available and preferred nowadays, silica gel plates and plates with layers... 

Keywords Continuous flow PCR DNA analysis DNA microarrays Genetic analysis Integrated microsystems Microcapillary electrophoresis Microfluidics Micro-PCR devices Solid-phase extraction... 

Fig. 5 Determination of the chemotactic sensitivity of E. colt, (a) Schematic of the microfluidic device. Chemoattractant and fluorescein were injected in the microcapillary via inlet C by means of a passive valve, (b) Flow in the main channel (from A to B) was used to transport E. coll past the entrance (M) of the microcapillary, (c, d) Epifluorescence images of the microcapiflary filled with...

A particular class of focusing device is represented by coaxial injectors (Figure 20.6), first implemented using microcapillaries in the context of microfluidics by Cramer et al." " ... 

In 1998, Anderson and Busch presented an offline TLC-MS probe composed of an array of microcapillaries [9]. This device lacked the general sensitivity of Luftmann s device because it only sampled the uppermost layer of the TLC plate. Nevertheless, it also planted the idea of MS imaging of sample spots from the developed TLC plates by an elution-based approach. Van Berkel further developed this concept in 2002 [10]. A liquid microjunction surface sampling probe enabled stepwise as well as continuous sampling mode of operation, which theoretically could be used for imaging analyses of whole TLC plates. The spatial resolution was a function of scan speed and the nature of the eluting solvent. This device underwent many improvements in the following years however, it has been never commercialized. 

Figure t. Microcapillary spotting device for TLC a) Capillary tube b) Septum c) Support tube d) Rubber bulb... 

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