There are a broad range of applications such as analytical sensors, biosensing and medical applications that require the monitoring of dissolved oxygen (DO) and pH using sensitive, stable, compact and low cost sensors. Here we develop full inkjet printing sensors to measure DO and pH. They have been fabricated using commercially available gold and platinum inks in plastic substrates. The inks are specially designed formulation which allows their sintering at temperatures as low as 150 and 190 °C for Au and Pt respectively. This is a key point in the development of low-cost sensors made on plastic and paper substrates. These sensors integrate in a single platform all the basic elements for pH and DO recording, allowing the measures without any external electrode. The DO is directly measured with a gold working electrode, and the pH sensors is achieved after electrodepositing iridium oxide film over platinum working electrode. The printed electrodes for DO sensing exhibits excellent linearity between 0 and 8 mg L _1 range, with correlation factors greater than 0.99, obtaining low limits of detection, 0.17 mgL _1 and a sensitivity of 0.06 A(mgL) _1. IrOx pH sensors exhibit a super-Nernstian response in sensitivity repeatedly and reversibly between 65 mV/pH in the pH range of 3 to 10. This work demonstrates that these sensors are suitable for the determination of DO and pH and provide a cost-effective solution for future electrochemical monitoring systems.
Lithographic patterns of electrically conducting polymers are obtained starting from films of insulating precursor polymers or from appropriate composites via laser irradiation. The precursor polymers yield conducting patterns directly, whereas in the composites the initially formed latent images have to be developed in a subsequent step. Vapors of pyrrole, thiophene, or aniline derivatives are used as gaseous developers. Laser ablation of the materials may be combined with the laser induced generation of electrical conductivity using the same exposure apparatus.
Three-dimensional lithographic patterns can be obtained using a new two component UV sensitive polymer system. The light-sensitive material consists of a chlorine containing conventional polymer, i.e., poly(chloroacrylonitrile) as a typical acceptor, and a heterocyclic or aromatic monomer as the donor, here pyrrole. This two component precomposite can be irradiated by either an excimer laser or the radiation of a high pressure mercury lamp. The resulting image, essentially a black and white pattern, can be developed in wet or dry (ion etching, ablation) modes giving resist patterns with a resolution in the micrometer range.
Patterns of different electrical conductivity can be converted into three-dimensional lithographic structures taking advantage of differential etching behavior of the electrically conducting versus the insulating areas under reactive ion etching conditions. Particularly suited substrates are intrinsically conducting polymers and composites thereof with common, insulating polymers. Initially, electrically conducting images are obtained via exposure of a photosensitive composite to visible of UV-light, followed by a subsequent (`dry') development step in the vapor of a suited monomer. The electrically conducting areas experience RIE-type etching and thus etch faster in an oxygen plasma than the insulating sections.
Patterns of electrically conducting polymers (100 S cm-1) can be obtained by irradiating thin layers of insulating poly (bis-ethylthio-acetylene) (10-14 S cm-1) with 488 nm Ar+-laser or 351 nm XeF-excimer laser radiation. On the other hand this polymer is a suitable material for laser-induced ablation (photodecomposition), whereby this excimer laser patterned insulating polymer can be made conductive by another Ar+-laser afterwards. The conducting tracks have a stable resistivity both in air (without encapsulation) and in moisture at various temperatures and even in corrosive atmospheres. With these techniques, using a computer-controlled linear positioning system, printed microcircuit boards with integrated passive electronic components can be obtained. Surface mounted devices may be integrated into such circuitry using conductive adhesives.
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