A breathable flexible glucose biosensor with embedded electrodes for long-term and accurate wearable monitoring

This paper reports a breathable flexible glucose biosensor with excellent flexibility and moisture/air permeability. The biosensor's electrodes are embedded in a flexible porous nanofiber polyimide substrate through electrospinning. The porous structure of this nanofiber substrate makes the biosensor breathable, effectively avoiding the body-fluid accumulation that can significantly affect measurement accuracy in long-term wearable monitoring. It also completely embeds the electrodes in the substrate preventing them from falling off, which frequently occurs in a surface-electrode structure, effectively avoiding degradation of sensing performance over time. The air-permeable film substrate was obtained by optimizing the manufacturing parameters, including spinning voltage, flow rate, solution concentration, and electrospinning distance. Three electrodes were then embedded on the flexible air-permeable substrate by inkjet printing to form the breathable glucose biosensor. The fabricated breathable flexible glucose biosensor was found to have excellent moisture (-3954.8 g/[m(2) x 24 h]) and air (-63.59 mm/s) permeability. A bending test verified the firmness of the embedded structure, and the microscopic connectivity and conductivity of the electrodes were stable. This breathable biosensor can precisely detect glucose in the linear range of 0-25 mM with a detection limit of 0.128 mM.