A microfluidic system for analysis of electrochemical processing using a highly sensitive optical fiber microcavity

After months of work on the article, Martin and Andrzej finally got their second paper about electrochemical and optical studies using an optical fiber accepted. The article “A microfluidic system for analysis of electrochemical processing using a highly sensitive optical fiber microcavity” will be published in the journal “Optics and Lasers in Engineering” ¹ and it was written together with Mateusz Śmietana, Tomasz Gabler, Monika Janik and Marcin Koba (all from Warsaw University of Technology).

The article is a summary of the works done last year in the framework of of our common project with the Śmietana group at WUT. We created a new multi-domain sensor combining electrochemical and optical methods, which main part is a microcavity made in an optical fibre, incorporated into microfluidic system (Fig. 1.). The sensor is based on the concept of an in-line Mach- Zehnder interferometer and it is a direct upgrade from our previous device described in the first article in Lab on a Chip ² , where we put microelectrodes inside the microcavity.

This time we used band electrodes outside the cavity to induce redox reactions and analyse the products of these reactions optically after they flow inside the microcavity. By the addition of microfluidic system, we are able to control the flow of the analysed solution and get rid of problems such as evaporation of the liquid. We showed in the article, that after addition of microfluidic system, the sensor is still highly sensitive to small changes of refractive index in the cavity (with sensitivity over 14,000 nm/RIU). We also proved that the process of exchanging solution in the cavity is so fast, that the orientation of the cavity is not important. And most importantly, we showed for both redox probe and dopamine that we are able to detect products of electrochemical reactions also optically, which is promising for future highly sensitive studies of analytes in a microchannel.

1. A. Krześniak, T. Gabler, M. Janik, M. Koba, M. Jönsson-Niedziółka, M. Śmietana
   A microfluidic system for analysis of electrochemical processing using a highly sensitive optical fiber microcavity, Opt. Lasers Eng. 158 107173 (2022) (link – OA)(ChemRxiv – preprint)
2. T. Gabler, A. Krześniak, M. Janik, A. Myśliwiec, M. Koba, J. Buczyńska, M. Jönsson-Niedziolka*, M. Śmietana*
   Electrochemistry in an optical fiber microcavity – optical monitoring of electrochemical processes in picoliter volumes, Lab Chip 21, 2763-2770 (2021). (link, ChemRxiv – OA) (blog)