Relying on the piezoelectric effect to convert an applied electrical field into a mechanical strain, the micro diaphragm pump generates pressure in the pump chamber by moving its silicon membrane up or down, drawing in ambient air through a valve and compressing it in the pump chamber before expelling it.
“Our smart pump measures only 25 square millimeters, making it the world’s smallest pump. That said, it still has a high compression ratio,” says Dr. Martin Richter, department head of micro dosing systems at the Fraunhofer Research Institution for Microsystems and Solid State Technologies EMFT in Munich.
Conventional micro diaphragm pumps powered by piezoelectricity generate only relatively low pressure with air; the asymmetry of the piezo effect means a lot of room is required in the pump chamber to move the membrane. This results in a high dead volume within the chamber. Richter and his team came up with a trick to reduce this dead volume and increase the pump’s suction capacity. “We use the piezo effect to specifically preload the diaphragm when assembling the piezoceramic. The advantage of this is that we no longer need a deep pump chamber. This trick enables us not only to build micropumps with high compression ratios but also to make them smaller in size.”