Inkjet printing of Pd/SO₃H-modified graphene on different polymeric substrates to construct flexible electrochemical sensors

The hydrophilic nature of sulfonated (SO₃H) graphene was exploited to prepare aqueous inks with high concentrations and the development of disposable, flexible, and enzyme-free electrochemical glucose sensors is described. The inks were printed on the flexible substrates using inkjet printing method. Different polymeric flexible substrates, polyethylene terephthalate (PET) film, and polypropylene-based crystal clear A4 folder (CCF) were used as substrates. Micron-scale (~ 4 µm) electrode thickness with an average surface roughness of 14 nm was obtained. The changes in the sheet resistances of Pd/SO₃H-rGO@PET and Pd/SO₃H-rGO@CCF after bending cycles were found to be 6.8% and 2.0%, respectively, confirming the high bending resistance of the deposited layers. The results showed that developed flexible sensors showed high electrocatalytic activities against glucose. Furthermore, CCF-based flexible sensors showed higher sensitivity [y (nA) = 0.52x (mM) + 12.15) with a wider linear range of 1–20 mM compared to PET-based sensors. Graphical abstract: Preparation and the performance of flexible electrodes.[Figure not available: see fulltext.].