Monolithic Integration of Micro-Channel on Disposable Flow Sensors for Medical Applications

We report on the integration of a micro flow channel with a thermal flow sensor chip. Two different technologies were investigated: First the fluid channel is performed at the back side of the standard HSG-IMIT flow sensor chip using a double KOH etching process (DKOH). The second technology consists of a bond process between the flow sensor die and a polydimethylsiloxane (PDMS) sheet containing the channel. Both sensor types can be used for detecting flow rates in the range of 0.1- 5.0 mu1/min (H₂O) and/or pressure differences of 10-600 Pa. Compared to our previous sensor design [1] this leads to reduced packaging costs, increased reproducibility (better than 1%) and in particular a higher sensitivity at low flow rates. Finally a concept of an adhesive-free packaging of the sensor is presented.