The highly sensitive thermal-flow sensor microchips can detect bubbles and measure noninvasively through the wall of a flow channel inside a microfluidic substrate. The sensors are suitable for monitoring flow rates in high-volume biomedical applications and micro fuel cells. Noninvasive flow sensing is possible thanks to the high sensitivity achieved with the firm’s CMOSens technology. A 2.2 × 3.5-mm digital CMOSens microchip is bonded to the microfluidic channel substrate. Beside the sensor element, it houses the complete digital intelligence as well as the memory necessary for signal linearization, temperature compensation, and self-test algorithms. The chip provides a fully digital I²C interface and can operate over a supply voltage of 2.8 to 3.3 V. Electrical contact is made via metallization on top of the microfluidic substrate. Fluidic ports on bottom facilitate easy integration of discrete sensors for manifold designs if necessary. The sensor boasts a short flow-sensing response time of around 30 milliseconds, and sensor resolutions down to 0.5 nl/min are feasible.
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