Inkjet-printed flexible silver electrodes on thiol-enes

Flexible and conductive silver electrodes were fabricated by inkjet printing on several different compositions of thiol-ene polymers. Conductive electrodes with resistivity down to 30 µΩcm and good adhesion of the electrodes were obtained by optimizing the printing parameters. The maximum printing resolution was 100 µm lines and 80 µm gaps between the lines. Printing on top of cross-linked off-stoichiometric thiol-ene polymer was tested for compositions ranging from 30 % thiol excess to 5 % allyl (‘ene’) excess. The roughness off the thiol-ene surfaces was shown to greatly improve the quality of the printed electodes: consistently high yield of conductive electrodes was obtained on rough surfaces (roughness ≈ 1 µm), whereas on smooth surfaces the electrodes were often cracked. The lowest resistivity values were obtained on electrodes printed on near stoichiometric thiol-ene substrates. The conductivity of the electrodes was retained after 5 % linear strain and after repeated bending with 1 mm radius of curvature, showing the potential for flexible sensors. The electrodes were also applied to electrical impedance-based monitoring of cell growth on thiol-ene surfaces, which showcased that the electrodes survive stressed cell culture conditions for at least 36 h.