Fabrication and testing of a SU-8 thermal flow sensor

Ikerlan S. Coop. (CIC microGUNE), Paseo J.M. Arizmendiarrieta 2, 20500 Mondragón (Guipuzcoa), Spain
Sensors and Actuators B Chemical (Impact Factor: 4.1). 06/2010; 147(2):411-417. DOI: 10.1016/j.snb.2010.03.054


In this work, a microthermal flow sensor integrated in a completely polymeric based microfluidic chip is presented. The fabrication process is based on photolithography of SU-8 layers to pattern the fluidic channels, surface treatment processes in order to improve adhesion of metal layer on top of the polymer, and the use of an adhesive bonding of two patterned SU-8 layers, allowing an easy packaging and integration with other SU-8 based devices like micropumps, microvalves, etc. Characterization of the device shows its successful performance detecting flows in the order of tens of μl/min, working at heater temperatures from 60 °C down to 40 °C. Moreover, the sensor exhibits a linear response at flows below 25 μl/min and the detection of volumes in the range of nanoliters. Such characteristics of the sensor are of great interest for its use in biological applications.

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Available from: Luis J Fernandez, Apr 15, 2015
    • "They achieved a maximum resolution of 100 nl·h -1 with a sensitivity of 0.53 K·(µl·min -1 ) -1 at a limited flow rate range between 83 nl·min -1 and 1.5 µl·min -1 [34]. A slightly wider working range of about 40 nl·min -1 up to 2 µl·min -1 with a resolution of 40 nl·min -1 of was reported by Vilares et al. and Dijkstra et al. [24] [25]. Increased working ranges could be implemented by Ahrens et al. and Meng et al. "
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    • "Evaporation of 20 nm of titanium (that acts as an adhesion layer) and 200 nm of gold were subsequently performed using an electron beam gun in a Univex 450B coating system (Oerlikon Leybold, Germany). However, before evaporation, a low-power oxygen plasma etching was applied to the wafer to improve metal adhesion to the SU-8 surface (Vilares et al. 2010). Afterwards, patterning of the metal layer was performed by using a standard photolithography process and different selective wet chemical etchings. "
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