"Our smart pump measures only 25 square millimeters,
Richter and his team use the piezoelectric effect, which converts an applied electrical field into mechanical strain, to generate pressure in the pump chamber. Alternating the voltage helps move the silicon membrane up or down, which in turn draws in ambient air through a valve and compresses it in the pump chamber before expelling it.
Using tricks to increase pressure
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 inevitably results in a high dead volume, in other words a high volume of residual gas 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."
Not just the diaphragm but also the flap valves and the pump chamber are made of monocrystalline silicon, which offers numerous benefits over metals and plastics. For one, the metalloid – which is also used to make solar cells and computer chips – is pliable and fatigue-free. For another, the individual pump components can be etched from the silicon layer with a high degree of precision and subsequently joined together.
However, its disadvantage is the relatively high cost of silicon, which is why it is crucial to make the pump as small as possible. "Our goal is to reduce the size of the pump to 10 square millimeters to make its mass production profitable. We are well on track to achieving this," Richter says.
Read more at: https://phys.org/news/2017-10-powerful-micro-diaphragm-mini-sensors.html#jCp
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