Micro-scale liquid flow sensors

February 10, 2014 // By Graham Prophet
Swiss sensor manufacturer Sensirion’s liquid flow series LPP10 and LPG10 are based on planar microfluidic substrates and the sensors are available with a glass (LPG10) or a plastic (LPP10) packaging.

The glass version is extremely durable, while the plastic version is more suitable for disposable applications and is very cost-effective in high volume. Both versions are ideal for various medical and biomedical applications. With a form factor of 10 x 10 mm, both  sensors have no moving parts and no obstacles in the flow path of the fluid.

Packaging technology enables Sensirion's  thermal flow sensor microchips to measure non-invasively through the wall of a flow channel inside a microfluidic planar substrate. This design provides unique sensitivity for liquid flow measurement and bubble detection in the range of 0 to 1000 microlitres per minute. The sensors are suitable for monitoring flow rates and improving system performances in biomedical and life science applications.

Non-invasive flow sensing is possible thanks to the high sensitivity achieved with CMOSens Technology. A small digital CMOSens microchip (2.2 x 3.5 mm) is bonded to the microfluidic channel substrate. In addition to the sensor element, it houses the  digital intelligence and the memory necessary for signal linearisation, temperature compensation and self-test algorithms. The chip provides a digital I²C interface. Electrical contact is made via metallisation above the microfluidic substrate. Fluidic ports below facilitate integration of discrete sensors into numerous designs. The sensor has a flow sensing response time of 30 msec, and sensor resolutions down to 0.5 nl/min are feasible. A digital microsensor chip provides a calibrated digital output, eliminating the need for additional signal conditioning.

This significant simplification of liquid flow sensing technology enables extremely small and efficient sensor solutions. Customised solutions based on this technology can also be developed for various applications; standard versions are available immediately.

Sensirion; www.sensirion.com/lpx