Since the emergence of Lab-On-Chip applications for biomedical protocols, electrowetting on dielectric-digital microfluidic (EWOD-DMF) systems have been implemented in many domains such as enzyme assays, immunoassays, DNA-based applications, cell-based assays, tissue engineering and proteomics [1,2]. Thus, Digital MicroFluidic (DMF) Lab-On-Chip devices have been coupled with off-line Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) analysis as an alternative to optical methods [3]. MALDI-MS analysis brings the advantage of time reduction, less complexity of sample preparation and high sensitivity. Even though this system is a pioneering one in the LoC applications for MS analysis, several drawbacks can be underlined: proteins or peptides concentrations remain still quite high (> nmol/µL) and the analysis protocol is somewhat time consuming and complicated due to manipulation of viscous matrix and to proteins drying on the surface.

In this presentation, I will discuss an original study consisting of coupling EWOD-DMF and matrix-free Laser Desorption/Ionization Mass Spectrometry (LDI-MS) analysis using superhydrophobic nanostructured silicon substrates. Compared to a classical hydrophobic surface, it leads to an improvement of the microfluidic actuation (both in terms of minimal applied voltage threshold and droplet speed) and it allows a matrix free LDI-MS analysis of very low concentration of peptides sample (down to fm/µL) through a rapid and simple protocol (without addition of any organic matrix) [3-6].

[2] V. Srinivasan, V. Pamula, and R. Fair, Lab Chip 4 (2004) 310-315.

[3] A. R. Wheeler, H. Moon, C. A. Bird, R. R. O. Loo, C. J. Kim, J. A. Loo, R. L. Garrell, Anal. Chem. 77 (2005) 534

[4] F. Lapierre, G. Piret, H. Drobecq, O. Melnyk, Y. Coffinier, V. Thomy and R. Boukherroub, Lab Chip11 (2011) 1620-1628.

[5] M. Jönsson-Niedziolka, F. Lapierre, Y. Coffinier, S. J. Parry, F. Zoueshtiagh, T. Foat, V.

      Thomy, R. Boukherroub, Lab-on-Chip 11 (2011) 490-496

[6] G. Perry, V. Thomy, M. R. Das, Y. Coffinier and R. Boukherroub (2011)

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