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Controlling the nanostructure of polymeric films using cost-effective deposition methods, like inkjet printing, has proven challenging due to the relative low resolution of such techniques. In this study, we combine inkjet printing with the use of nanopatterned substrates composed of TiO2 thin films on top of silicon wafers (NP-TiO2) for the preparation of polymeric films with similar surface morphologies. First, the evaporation induced self-assembly (EISA) process was used in the presence of a block co-polymer (polybutadiene-b-polyethyleneoxide) to prepare the NP-TiO2 substrates. The TiO2 ridges can be selectively modified with a hydrophobic perfluorinated phosphate, Zonyl FSE (ZFNP-TiO2). Conducting polymers (biotinylated polythiophene and polyaniline) were inkjet-printed both onto NP-TiO2 and ZFNP-TiO2 substrates, resulting either in continuous polymeric thin films or matrixes with separate droplets, respectively. The high surface energy determined for the NP-TiO2 substrate deemed it more suitable for the deposition of uniform and nanometer thin polymer layers. In fact, atomic force microscopy demonstrates that the deposited polymers are evenly distributed over the substrate surface while the nanopatterned structure is maintained. We conclude that the combination of inkjet printing and nanotemplating is a simple and cost-efficient way to fabricate nanopatterned polymer films with high potential in biosensing and electrical devices. [ABSTRACT FROM AUTHOR]

In this study, two different supramolecular recognition architectures for impedimetric detection of DNA hybridization have been formed on disposable paper-supported inkjet-printed gold electrodes. The gold electrodes were fabricated using a gold nanoparticle based ink. The first recognition architecture consists of subsequent layers of biotinylated self-assembly monolayer (SAM), streptavidin and biotinylated DNA probe. The other recognition architecture is constructed by immobilization of thiol-functionalized DNA probe (HS-DNA) and subsequent backfill with 11-mercapto-1-undecanol (MUOH) SAM. The binding capacity and selectivity of the recognition architectures were examined by surface plasmon resonance (SPR) measurements. SPR results showed that the HS-DNA/MUOH system had a higher binding capacity for the complementary DNA target. Electrochemical impedance spectroscopy (EIS) measurements showed that the hybridization can be detected with impedimetric spectroscopy in picomol range for both systems. EIS signal indicated a good selectivity for both recognition architectures, whereas SPR showed very high unspecific binding for the HS-DNA/MUOH system. The factors affecting the impedance signal were interpreted in terms of the complexity of the supramolecular architecture. The more complex architecture acts as a less ideal capacitive sensor and the impedance signal is dominated by the resistive elements. [ABSTRACT FROM AUTHOR]

Abstract Methylamine (MA) is highly toxic even at low concentrations. The current U.S.A. Occupational Safety and Health Administration Permissible Exposure Limit (OSHA PEL) is 10 ppm in the gas phase. In this study we have developed low-cost, robust and stable copper sulphide film on flexible plastic and paper substrate. The sensitivity of the film towards MA as a function of print density is studied at room temperature. The electrical and colorimetric response of the sensing films is optimized with respect to print density. The performance parameters of the sensing films including, sensitivity, a lower limit of detection (LOD), selectivity and onset time of detection are determined. X-ray photoelectron spectroscopy is employed for chemical characterization of the sensing film. It is demonstrated that copper sulphide films register either change in resistance or colour when exposed to methylamine in a range of 1 to 100 ppm. A LOD of 1 ppm is achieved which is lower than the current OSHA PEL. The optimized sensing film has shown over three and six orders of magnitude change in resistance when exposed to 10 ppm and 500 ppm of MA respectively. The low cost, room temperature operation, electrical and colorimetric response of the developed sensing films make them promising candidates to be used for medical diagnostics as well as industrial use for example in chemical industry and environmental applications. Highlights • Low-cost, mass producible and flexible sensing film. • An electro-optical sensing response at room temperature. • Highly sensitive methylamine sensor. • lower limit of detection of 1 ppm is achieved. [ABSTRACT FROM AUTHOR]

Low-cost and robust hydrogen sulfide (H 2 S) gas sensors can be utilized in different industrial applications. Earlier we have demonstrated an inexpensive wirelessly readable copper acetate based H 2 S gas sensor which was successfully employed for monitoring the quality of raw poultry. In this study we have thoroughly investigated and optimized the performance of inkjet-printed copper acetate based H 2 S gas sensor on flexible plastic substrate at room temperature. The effect of ink composition, print density, number of print nozzles and temperature of the substrate on sensor performance was tested. The long term stability of these sensors after exposure to H 2 S was studied extensively and was optimized as a function of the print density of copper acetate. The conversion of copper acetate to copper sulfide upon reaction with H 2 S was established by X-ray photoelectron spectroscopy. We believe that the optimized sensor developed in this study with respect to stability, repeatability and material consumption will pave the way for the commercial use of these sensors e.g. in food quality monitoring and environmental applications. [ABSTRACT FROM AUTHOR]

Abstract: An electrode platform printed on a recyclable low-cost paper substrate was characterized using cyclic voltammetry. The working and counter electrodes were directly printed gold-stripes, while the reference electrode was a printed silver stripe onto which an AgCl layer was deposited electrochemically. The novel paper-based chips showed comparable performance to conventional electrochemical cells. Different types of electrode modifications were carried out to demonstrate that the printed electrodes behave similarly with conventional electrodes. Firstly, a self-assembled monolayer (SAM) of alkanethiols was successfully formed on the Au electrode surface. As a consequence, the peak currents were suppressed and no longer showed clear increase as a function of the scan rate. Such modified electrodes have potential in various sensor applications when terminally substituted thiols are used. Secondly, a polyaniline film was electropolymerized on the working electrode by cyclic voltammetry and used for potentiometric pH sensing. The calibration curve showed close to Nerstian response. Thirdly, a poly(3,4-ethylenedioxythiophene) (PEDOT) layer was electropolymerized both by galvanostatic and cyclic potential sweep method on the working electrode using two different dopants; Cl− to study ion-to-electron transduction on paper-Au/PEDOT system and glucose oxidase in order to fabricate a glucose biosensor. The planar paper-based electrochemical cell is a user-friendly platform that functions with low sample volume and allows the sample to be applied and changed by e.g. pipetting. Low unit cost is achieved with mask- and mesh-free inkjet-printing technology. [Copyright &y& Elsevier]

Inkjet-printing of metal nanoparticles is a particularly promising technique for the fabrication and modification of surfaces with a multifunctional nature. Recently copper sulfide nanoparticles (CuS NPs) have attracted wide interest due to a range of valuable properties including long term stability, photo-thermal activity, ease of synthesis and low cost. In the present study, printed CuS patterns were successfully fabricated on latex coated paper substrates and characterized by means of atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), UV–Vis-NIR spectroscopy, and grazing incidence X-ray diffraction (GID). The resulted patterns displayed pronounced photo-thermal effect under Near Infrared Irradiation (NIR) even with relatively low laser power. Finally, by utilizing an automated real-time imaging platform it was possible to verify that the CuS printed film was not cytotoxic to human dermal fibroblast cells (HDF). The pronounced photo-thermal properties and nontoxic nature of these printed low-cost flexible CuS films make them promising candidates for fabrication of devices with localized photo-thermal effect suitable for biomedical applications. [ABSTRACT FROM AUTHOR]

Printed electrodes on a recyclable low-cost coated paper were used as a platform for constructing potentiometric ion sensors consisting of an ion-selective electrode (ISE) and a reference electrode (RE). The reference and working electrodes were printed by using a stable suspension of gold nanoparticles (AuNP) as the ink. Sintering turned the printed electrodes conductive. A poly(3,4-ethylenedioxythiophene) (PEDOT) layer, with poly(styrene sulfonate) (PSS) ions as counterions was deposited on the gold electrodes by electropolymerization, drop-casting or ink-jet printing. The reference electrode was prepared by further coating the PEDOT(PSS) layer with a poly(vinyl chloride) (PVC) membrane containing a lipophilic salt, tetrabutylammonium tetrabutylborate (TBA-TBB), thus resulting in a solid-contact reference electrode (SCRE). The working electrode was modified by coating the PEDOT(PSS) layer with a K + -selective membrane, to obtain a solid-contact K + -ISE. The electrochemical characteristics of the resulting electrode systems were studied by amperometric, potentiometric and electrochemical impedance spectroscopic (EIS) measurements. The potentiometric response toward K + ions was additionally studied. The surface structure of the PEDOT(PSS) layers deposited by the different methods was studied with atomic force microscopic (AFM) measurements. It was shown that a well-functioning planar electrode platform with good electrochemical characteristics could be prepared by ink-jet printing in a repeatable manner. The planar electrode platform presented here offers a user-friendly and ecological alternative to perform chemical analysis from small sample volumes. [ABSTRACT FROM AUTHOR]

The aim of this study was to prepare printable inks of the poorly water soluble drug indomethacin (IMC), fabricate printed systems with flexible doses and investigate the effect of ink excipients on the printability, dissolution rate and the solid state properties of the drug. A piezoelectric inkjet printer was used to print 1 × 1 cm 2 squares onto a paper substrate and an impermeable transparency film. l -arginine (ARG) and polyvinylpyrrolidone (PVP) were used as additional formulation excipients. Accurately dosed samples were generated as a result of the ink and droplet formation optimization. Increased dissolution rate was obtained for all formulations. The formulation with IMC and ARG printed on transparency film resulted in a co-amorphous system. The solid state characteristics of the printed drug on porous paper substrates were not possible to determine due to strong interference from the spectra of the carrier substrate. Yet, the samples retained their yellow color after 6 months of storage at room temperature and after drying at elevated temperature in a vacuum oven. This suggests that the samples remained either in a dissolved or an amorphous form. Based on the results from this study a formulation guidance for inkjet printing of poorly soluble drugs is also proposed. [ABSTRACT FROM AUTHOR]