Plasma polymers derived from oxazoline precursors present a range of versatile properties that is fueling their use as biomaterials. However, coatings deposited from commonly used methyl and ethyl oxazoline precursors can be sensitive to the plasma deposition conditions. In this work, we used various spectroscopic methods (ellipsometry, x-ray photoelectron spectroscopy, and time of flight secondary ion mass spectrometry) and cell viability assays to evaluate the transferability of deposition conditions from the original plasma reactor developed by Griesser to a new wider, reactor designed for upscaled biosensors applications. The physicochemical properties, reactivity, and biocompatibility of films deposited from 2-isopropenyl-2-oxazoline were investigated. Thanks to the availability of an unsaturated pendant group, the coatings obtained from this oxazoline precursor are more stable and reproducible over a range of deposition conditions while retaining reactivity toward ligands and biomolecules. This study identified films deposited at 20 W and 0.012 mbar working pressure as being the best suited for biosensor applications.

Electrochemical immunosensors are an emerging technology for the fast, sensitive, and reliable diagnosis of diseases from bodily fluids. These sensors work by detecting a change in current upon analyte binding to an immuno‐functionalized electrode. Current methods of electrode functionalization are lengthy processes involving self‐assembled monolayer formation and wet chemistry biofunctionalization. Herein, thin films deposited from the plasma phase of oxazoline precursors are investigated and optimized as an alternative approach for electrode functionalization. The plasma‐enabled method has the advantage of being substrate independent and allows the spontaneous binding of biomolecules in physiological buffer. Surface sensitive analysis techniques are employed to characterize the thickness, reactivity, and stability of the thin films before investigating their electrochemical properties on indium tin oxide and gold electrodes including the feasibility to reduce charge transfer resistance with gold nanoparticles. Last, these films are employed to develop an immunosensor for the detection of free epithelial cell adhesion molecule with a limit of detection of 8.7 ng mL−1.

In bioelectronics, conducting polymer coatings allow the reduction of the impedance of metallic electrodes and facilitate the translation of bioelectrical signals at their interface. Such coatings can be made using thin film deposition from a solution or direct synthesis via electrodeposition. The electrical control over the deposition offers the possibility for a fine‐tuning of the film's thickness and structure. However, the mechanical stability of such coatings mainly suffer from their poor adhesion to the electrode surface and film cracking. Here, an extended study on the kinetics of poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) electropolymerization and the evolution of its physicochemical properties is provided. The impedance spectroscopy closely follows the electrochemical variations during the PEDOT:PSS's film growth, described by modeled equivalent circuits. The film's properties change during polymerization in relation to the supporting electrode size, its surface chemistry, and the deposition time. The film growth structures polymeric morphology in a confluent layer with a strong thickness increase before reaching its mechanical surface failure. Before this point, the film remains stable over a hundred cycles of applied potential strain in a defined redox window. These evaluations benchmark the PEDOT:PSS film properties during its electropolymerization toward electrochemically tunable transducers for bioelectronics.