A chip-integrated highly variable thermal flow rate sensor

In this work, we present an approach for seamless integration of a highly variable flow rate sensor in chip based microfluidic devices. This novel, optically readable microfluidic calorimetric flow rate sensor is realized by a combination of an inkjet printed heating element with a fluorescent sensor layer inside microfluidic channels. This enables to read out flow rate induced variances in the temperature profile along the channels, which results in an unsurpassed wide working range of the microfluidic anemometer from the lower nl min(-1) range up to several 100 mu l min(-1). The system was thoroughly investigated and revealed high flexibility, stability, repeatability and sensitivity.