A drop-on-demand droplet generator for coating catalytic materials on microhotplates of micropellistor

The size of the microhotplates based on MEMS is micron-grade, typically rectangular membrane of 270 μm × 70 μm in micropellistors. Coating carrier catalytic materials on the microhotplate appeared to be an extremely critical step in practice. To solve this problem, this paper presents a droplet generator based on microfluidic pulse inertia force, which can be used for dispersing carrier catalytic materials into uniform fine droplets and coating them on the microhotplate. The principle of the generator is to actuate a hollow PZT stack by a signal generator and a voltage amplification to provide an enough pulse inertia force for a glass micro-nozzle and catalytic materials inside to eject droplets. The micro-nozzle was fabricated by glass heating process without complicated microfabrication technology. So it has the advantages of good chemical resistance, low friction, easy to manufacture and low cost. The porous Al2O3 matrix thickness and the amount of platinum palladium catalyst can be controlled accurately using the droplet generator. The micropellistor with original signal of 75 mV was fabricated and 36 mV was remained after aging treatment. The power consumption can remain as low as 75 mW as well.