Laboratory crystallization studies are important for understanding the rates, pathways and mechanisms of nanoparticle growth. Most studies have been done using simple batch reactors because they are easy to design and operate. A significant drawback of this approach is that they produce concentration versus time data that must be differentiated to obtain reaction rates. By comparison mixed flow reactors (MFR) are more complicated to construct but have the advantage of measuring rates directly. MFRs can also be coupled with different types of analytical characterization methods to measure structural, physical and chemical properties in real time. This information is essential for scientific investigations of important geochemical processes involving nanoparticle and mineral formation. We have designed and implemented several new types of MFRs for controlled nanoparticle synthesis and real time in situ characterization. Models of the MFR parts are created by computer-aided design software and converted to working physical models using desktop stereolithography 3D printing. We have also developed microfluidic “chips” that are relatively x-ray transparent, using a new polymer casting method. These new types of devices are highly adaptable, inexpensive, and easy to manufacture, compared to conventional machining. Our custom reactor designs have different sized channels and mixing configurations that enable nanoparticle synthesis at a wide range of chemical and flow conditions. Microfluidic-style devices with channel sizes of 1 mm or smaller create laminar flow where mixing of reagents is only by diffusion. Diffusion and mixing can be enhanced using the so-called lamination method, which involves splitting the influent solutions into series of smaller, interwoven streams. The conditions created in these devices are relevant to mineral precipitation (and dissolution) in relatively confined spaces such as in soil pores and rock fractures. More traditional, larger volume MFRs that create turbulent conditions can also be fabricated rapidly and inexpensively using desktop SLA 3D printing. Designs are highly customizable and can be shared easily between research groups. Synchrotron total scattering experiments on gold, calcium phosphates, and ferric hydroxylsulfates show that the reactor designs described here are suitable for real time in situ crystallization studies in a variety of chemical systems.

Custom micro- and millifluidic devices for controlled nanoparticle synthesis and real-time In situ characterization

256th National Meeting (2018)

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