Nanofluidic flowmeter using carbon sensing element

The field of nanofluidics dealing with nL fluids is growing, and sensors for monitoring ever smaller flow rates (∼nL/min) are needed. This paper presents a new, sensitive micromachined thermal sensor for measuring flow rates. The integrated sensor uses a high-TCR (temperature coefficient of resistance) carbon sensing element obtained from ion-implanted parylene. The ion-implanted carbon element has a high temperature coefficient of resistance of -2%/°C and is embedded in a freestanding microchannel suspended from the substrate. The developed sensor has been characterized for flow measurements with a volumetric flow sensitivity of 380 μV/(nl/min) under a constant current bias with a power consumption of only 28 μW. To our knowledge, this is the first such nanofluidic carbon flow sensor and its sensitivity is better than any of flow sensors reported to date.