Optical Cantilever MEMS Microphone

Superior performance when applied to photoacoustic gas detection

Cantilever sensor

High sensitivity is achieved by using a patented cantilever pressure sensor that is over hundred times more sensitive compared to a membrane, which is used in conventional techniques.

Gasera’s patented cantilever-type pressure sensor

Gasera’s patented cantilever-type pressure sensor is designed to significantly improve the sensitivity of photoacoustic spectroscopy (PAS). An extremely thin cantilever portion moves like a flexible door due to the pressure variations in the surrounding gas. The movement of the free end of the cantilever can be about two orders of magnitude greater than the movement of the middle point of the tightened membrane under the same pressure variation. This is because the cantilever only bends and does not stretch.

The sensor is made out of single crystal SOI-silicon with a specially developed dry-etching process that leads to a highly stable component; this is why the sensor is practically totally immune to temperature and humidity variations. In addition, the sensor is not suffering from wearing. The manufacturing process of the cantilever has been developed in co-operation with the Department of Micro- and Nanosciences of Aalto University in the research group of Micro and Quantum systems which is lead by professor Ilkka Tittonen.

Readout Interferometer

Gasera's laser based readout inteferometer

The displacement of the cantilever is measured optically to avoid the so called “breathing effect”, which occurs in capasitive measurement principle where the other electrode damps the movement of the sensor. For precise measurement of the cantilever movement Gasera has developed a laser based readout inteferometer which is able to accurately measure displacement from well under a pico-meter up to millimeters.

Together the cantilever sensor and the readout interferometer form an optical microphone that has demonstrated over hundred times better sensitivity compared to conventional microphone technology when applied to photoacoustic gas detection.