Design and characterization of a microreactor for monodisperse catalytic droplet generation at both elevated temperatures and pressures

We report the fabrication and characterization of a microfluidic droplet microreactor with potential use for single catalyst particle diagnostics. The aim is to capture Fluid Catalytic Cracking (FCC) particles in droplets and perform a probe reaction that results in a fluorescent output signal. The intensity of such a signal can be used as a measure of the catalytic activity of the particle. The microreactor features a droplet generator, platinum (Pt) microheaters, and Pt micro temperature sensors, and is able to operate at pressures up to at least 5 bar. Fluidic channels are etched in a silicon substrate, and platinum heater and sensor structures embedded in the glass cover. We have mapped the temperature inside the microchannels using nanoparticles that show temperature-dependent luminescence. At various spots on the chip, the temperature deviates by 0.86 degrees Celsius close to the Pt sensor and 5.5 degrees Celsius farther away from it. Experiments with making oil-in-water droplets at various temperatures and pressures result in stable droplets up to 100 degrees Celsius at atmospheric pressure. At this temperature, small gas bubbles are formed in the water phase, and then collected by the oil droplets. At a pressure of 5 bar, the droplets are stable up to at least 120 degrees Celsius. E-cat FCC particles were captured in water droplets at a rate of 150 droplets per second.