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Optofluidics, Microfluidics and Nanofluidics

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In-line characterization and identification of micro-droplets on-chip

Emanuel Weber
  • Corresponding author
  • Institute for Microsensors, -actuators, and -systems (IMSAS), MCB, University of Bremen Otto-Hahn-Allee, Build. NW1, 28359 Bremen, Germany
  • Email:
/ Dietmar Puchberger-Enengl
  • Institute of Sensor and Actuator Systems (ISAS), Vienna University of Technology Gusshausstrasse 27-29, 1040 Vienna, Austria
/ Franz Keplinger
  • Institute of Sensor and Actuator Systems (ISAS), Vienna University of Technology Gusshausstrasse 27-29, 1040 Vienna, Austria
/ Michael J. Vellekoop
  • Institute for Microsensors, -actuators, and -systems (IMSAS), MCB, University of Bremen Otto-Hahn-Allee, Build. NW1, 28359 Bremen, Germany
  • Email:
Published Online: 2013-06-25 | DOI: https://doi.org/10.2478/optof-2013-0002


We present an integrated optofluidic sensor system for in-line characterization of micro-droplets. The device provides information about the droplet generation frequency, the droplet volume, and the content of the droplet. Due to its simplicity this principle can easily be implemented with other microfluidic components on one and the same device. The sensor is based on total internal reflection phenomena. Droplets are pushed through a microfluidic channel which is hit by slightly diverging monochromatic light. At the solid-liquid interface parts of the rays experience total internal reflection while another part is transmitted. The ratio of reflected to transmitted light depends on the refractive index of the solution. Both signals are recorded simultaneously and provide a very stable output signal for the droplet characterization. With the proposed system passing droplets were counted up to 320 droplets per second and droplets with different volumes could be discriminated. In a final experiment droplets with different amounts of dissolved CaCl2 were distinguished based on their reflected and transmitted light pattern. This principle can be applied for the detection of any molecules in microdroplets which significantly influence the refractive index of the buffer solution.

Keywords: micro droplets; partial total internal reflection; refractive index; optofluidics


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About the article

Received: 2013-04-08

Accepted: 2013-04-26

Published Online: 2013-06-25

Published in Print: 2014-01-01

Citation Information: Optofluidics, Microfluidics and Nanofluidics, ISSN (Online) 2300-7435, DOI: https://doi.org/10.2478/optof-2013-0002. Export Citation

© 2013 Emanuel Weber et al.. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License. (CC BY-NC-ND 3.0)

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