The smallest pressure sensor in the world!

A pressure sensofr for measuring blood pressure drop in the coronary arteries has been developed in a project between The Royal Institute of Technology (KTH), Radi Medical Systems, and Acreo. The sensor is used in balloon dilatation, for monitoring of the blood pressure in "real time" during the surgery. Dimensions of the chip are 0.1x0.15x1.3 mm. This is now a commercial product.

The developmenft of the sensor started in a research project at KTH (prof Göran Stemme and Edvard Kälvesten) in cooperation with Acreo with the goal to measure turbulance in air flows. For this a combined pressure and flow sensor with a size of 100µm was designed and successfully presented. The fabrication was based on surface micromachining in silicon and piezoresistivity - MEMS. By redesigning the sensor it could fit into a small catheter used for balloon dilutation. The development was made in close copperation with the Uppsala based company Radi Medical Systems. Radi had already developed a small pressure sensor using bulk micromachining of a silicon and  fiber optical readout. An important advantage with the piezoelectrical sensor was the electrical contact to the instrument, allowing the catheter to be used as combined pressure sensor and guide-wire for balloon-dillutation. Also production yield could be improved.

By being able to measure the pressure drop in the coronary arteries the diagnosis can be much more precise than only relying on the x-ray image of the heart. For small pressure drops a balloon dilutation could even make more harm. The sensor has thererfore been well accepted by medical doctors and the sensor is used all over the world.

The sensor chip development at Acreo was focused on improvement of stability and manufacturing control, and a small scale production started in 1997. Assembly of the sensor was done at Radi. With the small size of the chip > 40000 chips could be put on one single wafer. In 2000 Silex Microsystem started as a spin-off company from Acreo, commercialising MEMS foundry production. The production was moved over to Silex.

Radi sold to St Jude

In january 2009 Radi Medical Systems was sold to St Jude Medical for 250 miljon dollar. Radi had 380 employees, with almost half at the headquarter in Uppsala. St Jude Medical has 13000 employees in the whole world. In Sweden St Jude is mostly known for the pacemaker business it took over from Siemens Elema in 1994.

The product is sold as PressureWire™