On-chip flow microreactors may increase space-time efficiency for reaction screening and compound library synthesis (e.g. for drug discovery) as they enable miniaturization and process automation. Cutting-edge microfabrication of highly chemically inert silicon-based microfluidics compatible with MEMS (microelectromechanical systems) and CMOS (complementary metal-oxide-semiconductor) fabrication technologies allows novel reactor designs and functionalities to be realized and thus the exploration of new chemical reactivities and testing of new compounds [1]. On-chip features such as electrically driven joule heaters, electrodes or field-enhanced nanophotonic surface textures may allow site-selective electrochemical surface functionalization [2,3], precise reaction control and on-line analytics.

Silicon-based milli- and microfluidic devices are developed for solid-phase synthesis of catalytically active surfaces. In contrast to frequently utilized glass channel walls as catalyst adhesion layers [4], we use metallic coatings along microchannels that permit the formation of segregated thin-films patterns to site-selectively functionalize surfaces along a single channel. The metallic adhesion layers thereby act as electrodes for electrosynthesis, catalyst immobilization and electrochemical analysis. These wall-coated microreactors with a high surface-to-volume ratio are employed to screen single- and multistep chemical reactions with organo- and organometallic catalysts. In addition, nanofabricated resonant plasmonic nanohole arrays embedded in the electrodes are designed to characterize catalyst monolayers by surface-enhanced Raman spectroscopy (SERS).

[1] R. Munirathinam, J. Huskens, W. Verboom, Adv. Synth. Catal., 2015, 357, 1093-1123.
[2] M. Hellstern, M. Gantenbein, L. Le Pleux, G. Puebla-Hellmann, E. Lörtscher, M. Mayor, Adv. Mater. Interfaces, 2019, 6, 1801917.
[3] M. Hellstern, M. Gantenbein, G. Puebla-Hellmann, M. Mayor, E. Lörtscher, “Electrochemical Deprotection for Site-selective Immobilization and Local Assembly of Molecules by Click-Chemistry” US Patent Application No. P201701725US01 (2018).
[4] R. Ricciardi, J. Huskens, W. Verboom, J. Flow Chem., 2013, 3, 127-131.