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4706919 
Journal Article 
3D printing of microfluidic devices with embedded sensing electrodes for generating and measuring the size of microdroplets based on contactless conductivity detection 
Duarte, LC; Chagas, CLS; Ribeiro, LEB; Coltro, WKT 
2017 
1 
Sensors and Actuators B: Chemical
ISSN: 0925-4005
EISSN: 1873-3077 
251 
427-432 
WOS:000406184600052 
This report describes the 3D printing of integrated microfluidic platforms containing microchannels and embedded sensing electrodes for capacitively coupled contactless conductivity detection ((CD)-D-4). Sensing electrodes were printed on poly(lactic acid) filament doped with carbon nanotubes and then integrated with fluidic channels printed on acrylonitrile butadiene styrene. The proposed microfluidic chips were explored to generate and measure the size of microdroplets based on (CD)-D-4 measurements. To the best of our knowledge, this is the first report showing the entire fabrication of an integrated platform by 3D printing as well as its use for measuring the size of droplets. The proof-of-concept was successfully demonstrated by generating oil droplets in an aqueous phase and water droplets in an oil phase. The droplet sizes were estimated based on their residence time within the detection cell in association with the flow velocity. According to the data achieved by (CD)-D-4 measurements, the length of water droplets decreased from 3.4 +/- 0.1 to 2.3 +/- 0.1 mm when the total flow rate raised from 15 to 55 mu L min(-1). For oil droplets, length values ranged from 3.6 +/- 0.1 to 2.4 +/- 0.1 mm at the same flow rate range. The achieved results exhibited an exponential correlation with the data obtained by optical measurements. (C) 2017 Elsevier B.V. All rights reserved. 
Additive manufacturing; Conductive polymer sensor; Droplet-based microfluidics; Electrochemical detection; Microemulsion; Rapid prototyping