This tiny diaphragm pump could enable medical device innovation

The world’s smallest micromembrane pump measures just 25 square millimeters. [Image from Fraunhofer]

Fraunhofer researchers have created a tiny yet powerful diaphragm pump that can deliver ambient air to gas sensors. The sensors are attached to a smartphone that warns a user of heavy exposure to particulate matter.

“Our smart pump measures only 25 sq mm, making it the world’s smallest pump. That said, it still has a high compression ratio,” said Martin Richter, department head of microdosing systems at the Fraunhofer Research Institution for Microsystems and Solid State Technologies EMFT, in a press release.

Richter also claims the pump could be used as a medical patch to continuously deliver small amounts of hormones and pain killers or even as an implant to regulate eye pressure in glaucoma treatment. It could also deliver scents through a headset for the gaming industry.

“A headset fitted with our smart pump could deliver precise doses of different scents close to the nose. The gaming industry has already expressed an interest in this,” said Richter.

The pump uses a piezoelectric effect that converts an applied electrical field into mechanical strain which creates pressure in the pump chamber. The silicone membrane moves up and down when alternating the voltage which allows for ambient air to flow into the pump through a valve where it is compressed in the pump chamber before being released.

“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,” said Richter.

Traditional micro diaphragm pumps that use piezoelectricity create low air pressures which means more room is needed in the chamber to move the membrane.

The Fraunhofer diaphragm features flap valves and pump chambers made of monocrystalline silicon that tends to be more beneficial than metals and plastics.

However, silicon is rather expensive which means the smaller the part, the less expensive it will be to produce it.

“Our goal is to reduce the size of the pump to 10 sq mm to make its mass production profitable. We are well on track to achieving this,” Richter said.

Smart sensor reaction times are too long in smartphones. Fraunhofer’s smart pump delivers air directly to the gas sensors to reduce reaction time to just 2 seconds. This allows for the sensors to detect particulate matter and can even alert the user of when the air in a room is too stale and needs to be ventilated.

The researchers also claim that the pump could detect alcohol content like a breathalyzer.

“However, this requires a high degree of measurement accuracy, which has not yet been achieved. Otherwise someone might decide to get behind the wheel of a car believing they measure just 0.3 per mille, when in fact they measure 0.9 per mille,” Richter said.

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