(i) (a) Schematic of the OOC system with modifications to incorporate the control with external elements and the spring load for the connectors on the top plate, (b) cross section of the bioreactor showing the position of the three DO printed sensors, and (c) real picture of the ExoLiver system with all fluidic and electrical connections.107 Reproduced with permission from Moya et al., Lab Chip 18(14), 2023–2035 (2018). Copyright 2018 the Royal Society of Chemistry. (ii) (a) Measurement setup with microsensor device placed in the 96-well cell culture plate. (b) Close-up scheme of microsensor tip with electrode layout.208 Reproduced with permission from Weltin et al., Biosens. Bioelectron. 87, 941–948 (2017). Copyright 2016 Elsevier. (iii) Design, fabrication, and control of the automated microfluidic EC biosensor. (a) Photograph of the lectrochemical (EC) microfluidic chip bonded with a microelectrode. (b) Labeling of the microfluidic channels and the valves with corresponding flowing solutions for fully automated biosensing measurements. (c) Three-layered microfluidic chip consisting of the microfluidic channel, a thin membrane, and the valve channel layer. (d) Schematic of the microfluidic EC biosensing system integrated with organ-on-a-chip for continual monitoring of a target biomarker in an automated manner. (e) A schematic illustration for immobilization of antibodies using streptavidin on the surface of the microelectrodes.209 Reproduced with permission from Shin et al., Adv. Sci. (Weinh) 4(5), 1600522 (2017). Copyright 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. (iv) (a) Design of reconfigurable microfluidic co-culture system. (b) A typical microfluidic device used in a co-culture experiment. The wall separating microchannels was lowered to demonstrate the food dye did not mix. (c) Principle of TGF-β detection. The binding of cytokine molecules causes aptamer molecules to change conformation.8 Reproduced with permission from Zhou et al., Lab Chip 15(23), 4467–4478 (2015). Copyright 2015 the Royal Society of Chemistry.