Microchannel silicon-glass

Multiphase packed-bed or trickle-bed microreactor [29, 30] Standard porous catalysts are incorporated in silicon-glass microfabricated reactors consisting of a microfluidic distribution manifold, a single micro-channel reactor or a microchannel array and a 25-pm microfllter. The fluid streams come into contact via a series of interleaved high aspect ratio inlet chaimels. Perpendicular to these chaimels, a 400-pm wide channel is used to deliver catalysts as a slurry to the reaction chaimel and contains two ports to allow cross-flow of the slurry. High maldistribution, pressure drop and large heat losses may occur... 

Microchannels are generally fabricated in silicon, glass or poly(dimethyl siloxane) (PDMS). Glass and PDMS provide transparency for optical monitoring, and the latter is also permeable to the oxygen and carbon dioxide that is... 

Combination of immunoassay and microfluidic platforms offers advantages related to the selectivity and sensitivity, associated to the antigen-antibody interaction with the remarkable features stated above for microfluidic platforms. Microfluidic immunoassays make use of a network of microchannels and/or immunoreactor chambers usually built in a monolithic platform (similar or even the same designs used in ME) from different materials as silicon, glass, or polymers with part of all the necessary components of an immunoassay... 

Micropumps based on piezoelectrics are made of pumping chambers that are actuated by three piezoelectric lead zirconate titanate disks (PZT). The pump consists of an inlet, pump chambers, three silicon membranes, three normally closed active valves, three bulk PZT actuators, three actuation reservoirs, flow microchannels, and outlet. The actuator is controlled by the peristaltic motion that drives the liquid in the pump. The inlet and outlet of the micropump are made of a Pyrex glass, which makes it biocompatible. Gold is deposited between the actuators and the silicon membrane to act as an upper electrode. Silver functions as a lower electrode and is deposited on the sidewalls of the actuation reservoirs. In this design, three different pump chambers can be actuated separately by each bulk PZT actuator in a peristaltic motion. 

Fig. 12 a. All-glass microchannels formed by DRIE with back-etched silicon... 

MicroChannel reactors have some significant drawbacks. The most troublesome is clogging of the channels via incoming particulate matter or from fouling during the reaction process. Robustness is another common problem with microreactors. Because the unit is made at such a small internal scale, the resistance to mechanical shock is low. These issues usually render the microchannel reactor unsuitable for reactions that have precipitates as a product. For the Prox reaction, microchannel reactors are suitable provided there is no water condensation and the incoming reformate is particulate free, especially from carbon. Since microchannel reactors are often made from substrates that include stainless steel, Hastelloy, glass, silicon, polymers, and ceramics, another issue that could arise is chemical compatibility. 

---