PH sensing for healthcare applications requires sensors with mechanically stable materials of high sensitivity and high reproducibility combined with low-cost fabrication technologies. This work proposes a fully printed pH sensor based on a specially formulated conducting polymer deposited on a microelectrode in a flexible substrate. A formulation, which combined polyaniline (PANI) and polypyrrole (PPy) with integrated polyelectrolyte poly(sodium 4-styrenesulfonate) (PSS), was specially prepared to be printed by inkjet printing (IJP). The sensor has good sensitivity in the physiological region (pH 7–7.5) key for the healthcare biosensor. This mixture printed over a commercial gold ink, which has a singular chemical functionalization with phthalocyanine (Pc), increased the sensor sensitivity, showing an excellent reproducibility with a linear super-Nernstian response (81.2 ± 0.5 mV/pH unit) in a wide pH range (pH 3–10). This new ink together with the IJP low-cost technique opens new opportunities for pH sensing in the healthcare field with a single device, which is disposable, highly sensitive, and stable in the whole pH range.

Bioanalytical methods, in particular electrochemical biosensors, are increasingly used in different industrial sectors due to their simplicity, low cost, and fast response. However, to be able to reliably use this type of device, it is necessary to undertake in-depth evaluation of their fundamental analytical parameters. In this work, analytical parameters of an amperometric biosensor based on covalent immobilization of glucose oxidase (GOx) were evaluated. GOx was immobilized using plasma-grafted pentafluorophenyl methacrylate (pgPFM) as an anchor onto a tailored HEMA-co-EGDA hydrogel that coats a titanium dioxide nanotubes array (TiO₂NTAs). Finally, chitosan was used to protect the enzyme molecules. The biosensor offered outstanding analytical parameters: repeatability (RSD = 1.7%), reproducibility (RSD = 1.3%), accuracy (deviation = 4.8%), and robustness (RSD = 2.4%). In addition, the Ti/TiO₂NTAs/ppHEMA-co-EGDA/pgPFM/GOx/Chitosan biosensor showed good long-term stability; after 20 days, it retained 89% of its initial sensitivity. Finally, glucose concentrations of different food samples were measured and compared using an official standard method (HPLC). Deviation was lower than 10% in all measured samples. Therefore, the developed biosensor can be considered to be a reliable analytical tool for quantification measurements.

This article describes the development of silicone gel-based inks for direct ink writing (DIW) with tunable viscoelastic properties that mimic the mechanical behavior of a wide range of soft tissues.