Simplification of Liquid Flow Sensors with Planar Package Technology
Simplicity for high-volume products
Sensirion has developed a simplified liquid flow sensor technology which is available for projects starting at an annual demand of 10'000 sensors.
As for all our liquid flow sensor products the high sensitivity of the CMOSens microsensors, allows to thermally measure flow rate non-invasively through the walls of a flow channel with full media isolation. The channel can be made from inert or bio compatible materials such as glass, plastic, ceramic, or steel.
As shown above, the flow channel can also be formed inside a planar substrate, such as is well known in lab-on-chip technology. As long as the thickness of top layer covering the channels is not more than 50-100 μm, the microsensor chip can be bonded to the outside and reliably measure through this layer. Metallic circuitries on the outer surface of the planar substrate provide electrical connection between the microsensor chip and the outside world (connection using flip-chip bonding).
Flow sensors based on this new planar packaging technology combine mechanical robustness, electrical contacts and fluidic connections in a device consisting of just two parts: a planar microfluidic substrate containing the flow channel and a microsensor chip that measures non-invasively through the top layer of the microfluidic substrate.
Two core technologies are merged at this point, with microfluidics chips and digital microsensor chips bonded directly together. Communication is provided by Sensirions I²C bus interface to read out linearized and temperature-compensated flow rate values.
Microfluidic chips with flow channels as described before can be produced using standard manufacturing processes according to the specific requirements of the application. For example, the sensor channel substrate can be a separate lab-on-chip system with supplementary flow sensing capability, or as shown in the photo left, it can be a simple flow channel substrate that forms the basis for a discrete, miniaturized flow sensor element. With the fluid inlet and outlet on the bottom side, discrete bio-compatible sensor elements of this sort can reliably be integrated into any fluid manifold system.