Sylgard 184 silicone kit

The PDMS composite was prepared by mixing with 10:1 weight ratio of base and cross linker (Sylgard 184 silicone kit, Dow Corning) and mixed in a planetary mixer (Thinky ARE-250) for 1 minute at 2000 rpm. After that, silver powder (2–3.5 micron, Sigma Aldrich) was dispersed by pre-mix for 30 seconds at 500 rpm, and full mixing for 10 minutes at 2000 rpm and degassing for 30 seconds at 2000 rpm. The viscous paste obtained was stored in a freezer at −24 °C for 30 minutes and then thawed. Prior to usage, the Ag-PDMS paste was mixed for 5 minutes at 2000 rpm and degassed for 30 seconds at 2000 rpm. The mechanical properties of PDMS composites were measured by a Universal Testing Machine. The viscosity of PDMS composites was measured by a coaxial cylinder rotational viscometer. Five samples were made for each resistance measurements.

All reagents and solvents were purchased in a highest available purity and used without further processing. The monomers 4,4′-methylenediphenyl diisocyanate (MDI), poly(4-vinylphenol) (PVP), 4,4′-dihydroxy-2,2-diphenylpropane (bisphenol A, BPA) and solvent (tetrahydrofuran, THF) were purchased from Merck Chemicals and Life Science GesmbH (Vienna, Austria). The cross linker 1,3,5-trihydroxybenzene (phloroglucinol, PG), and pyridine catalyst were purchased from Fluka (Vienna, Austria). The artificial bacterial cells were prepared by using polydimethylsiloxane (PDMS). The required silicone elastomer kit (Sylgard 184 silicone kit) was obtained from Dow Corning (Wiesbaden, Germany). Bacteria E. coli strain W (ATCC 9637), strain B (EC 11303) and Bacillus subtilis (ATCC 6633) were purchased from Sigma-Aldrich Handels Gmbh (Vienna, Austria). AT-cut quartz crystals with 15.5 mm diameter and 168 μm thickness were purchased from Zhejiang Quartz Crystal Corporation (Taizhou, China). Electrodes were screen printed on the quartz crystal microbalance (QCM) using GGP 2093-12% brilliant gold paste (Heraeus, Hanau, Germany).