Microfluidic synthesis

Xiang, Y. LaVan, D., Parallel microfluidic synthesis of conductive biopolymers, Proc. 2nd IEEE/ASME International Conference on Mechatronic and Embedded Systems and Applications 2006, 1-5... 

Fig. 9 Reactions in microdroplets. (a) Schematic showing enhanced mixing and suppressed dispersion in droplets. Reproduced with permission from [47]. (b) Millisecond kinetics on droplet microfluidics. Reproduced with permission from [53]. (c) Droplet-based microfluidic synthesis of anisotropic metal nanocrystals. Reproduced with permission from [94]...

Chan, E.M., A.P. Alivisatos, and RA. Mathies, High-temperature microfluidic synthesis of CdSe nanocrystals in nanohter droplets. Journal of the American Chemical Society, 2005,127 13854—13861. 

Z. Nie, W. Li, M. Seo, S. Xu, and E. Kumacheva, Janus and ternary particles generated by microfluidic synthesis Design, synthesis, and self-assembly. Journal of the American Chemical Society, 128, 9408-9412, 2006. 

The reasons why small-volume microfluidic synthesis is preferred are ... 

The percentage yield or percentage atom economy is a widely reported quantitative metric for evaluating a microfluidic synthesis route and comparing it with conventional-scale synthesis. In the case of parallel reactions, the evaluation criterion with respect to obtaining the desired product is the percentage selectivity. The figures of merit are defined below ... 

Microfluidic synthesis Microparticle synthesis Nanoparticle synthesis Particle synthesis... 

Similar approaches can be used in the microfluidic synthesis of Janus particles where two compartments are formed within the particle that have different compositions. In this case immiscible monomers are passed along microfluidic channels in parallel streams and then subsequently polymerized. This approach allows precise control over the volumetric fraction of each monomer by controlling the relative flow rates of the two monomer streams [3]. Polymerization is usually by UV irradiation, and the surfaces of each compartment of the Janus particles can be subsequently functionalized or used for immobilization of biomolecules. They can also be loaded with dyes or other small molecules to act as colorimetric indicators or in microencapsulation of drugs [3]. 

Once formed, microgel particles can be useful as scaffolds in the constructimi of other particles. A useful variant on the emulsification/ gelation approach to microfluidic synthesis of particles is the use of double emulsions in which it is possible to carefully adjust the size, monodispersity, and chemical composition within a microfluidic framework [3]. fri this case, microgel particles may form a stmctural scaffold to shift the relative position of the inner droplet in the emulsion and thus help to control the morphology of the particles subsequently produced. 

Park J, Saffari A, Kumar S, Gtmther A, Kumacheva E (2010) Microfluidic synthesis of polymer and inorganic particulate materials. In Clarke D, Ruble M, Zok F (eds) Annual review of materials research. Annual Reviews, Palo Alto... 

Fig. 4 Numerical simulations to calculate the pulse frequency for optimised mixing for the microfluidic synthesis of ZnO nanoparticles (a) 1 Hz pulse mixing, (b) 3 Hz pulse mixing and (c) 5 Hz pulse mixing. Reproduced with permission from ref. 19. Copyright 2014 Royal Society of Chemistry...

S.A. Khan, K.E. Jensen, Microfluidic synthesis of titania shells on colloidal silica. Advanced Materials, 2007, 19, 2556. 

Ti02 nanopartides [10-12], NiO nanopartides [13] and various nanopartides of metal oxides [14] are formed in droplets or in a micellar environment. Cottam et al. reported a microfluidic synthesis of small nanorods of titanium oxide by fast mixing of an oleic add solution of tetraisopropoxytitanium (TTIP) with trimethylamine N-oxide dihydrate (TMAO) [15]. Both reaction solutions were mixed by a Y-shaped micro channel structure and conducted through a 40 cm microchannel with an internal channel width of 100 Jim. As a result, bunched assemblies of rod-like titanium dioxide were obtained. The length of the bundles was more than 100 nm and the diameter of the single rods was less than 10 nm. 

M. Bouquey, S. Serra, L. Prat, G. Hadziioannou, Microfluidic synthesis and assembly of reactive polymer beads to form new structured polymer materials, in Book of Abstracts of the 9th International Conference on Microreaction Technology, IMRET 9, 6-8 September 2006, Potsdam/ Berlin, 2006, pp. 104—105. 

S.A. Khan, A. Gunther, M.A. Schmidt, K.F. Jensen, Microfluidic synthesis of collodial silica, Langmuir 2004, 20, 8604-8611. 

Haseloh S, Ohm C, Smallwood F, Zentel R (2011) Nanosized shape-changing colloids from liquid crystalline elastomers. Macromol Rapid Commun 32(l) 88-93 Ohm C, Kapemaum N, Nonnenmacher D, Giesselmann F, Serra C, Zentel R (2011) Microfluidic synthesis of highly shape-anisotropic particles from liquid crystalline elastomers with defined director field configurations. J Am Chem Soc 133(14) 5305-5311. doi 10.1021/ jal095254... 

Figure 6.16 Microfluidic synthesis and conversion of diazomethane (28) in the Pd-catalyzed cydopropanation of styrene (31). (Courtesy of S. Ldbbecke.)...

The presented results clearly show that photooxygenation can be carried out continuously in microfluidic devices, delivering high yields of the desired products. Moreover, the microfluidic synthesis steps can easily be integrated in continuous multistep processes. Thus, microstructured reactors are considered as important tools in the synthesis of fine chemicals and pharmaceuticals. 

Microfluidic synthesis of polymers with controllable molecular weight and compositions requires efficient mixing. There are a number of strategies for the enhancement of mixing in microchannels, which involve either passive or active elements [18,19]. 

Khan SA, Guenther A, Schmidt MA, and Jensen KF 2004 Microfluidic synthesis of colloidal silica. Langmuir, 20, pp. 8604-8611. 

Song, Y., Doomes, E.E., Prindle,)., Tittsworth, R., Hormes, J. and Kumar, C.S.S. (2005) Investigations into sulfobetaine-stabihzed Cu nanopartide formation toward development of a microfluidic synthesis. The Journal of Physical Chemistry B, 109, 9330-8. 

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