Parylene C as a versatile dielectric material for organic field-effect transistors.

An emerging new technology, organic electronics, is approaching the stage of large-scale industrial application. This is due to a remarkable progress in synthesis of a variety of organic semiconductors, allowing one to design and to fabricate, so far on a laboratory scale, different organic electronic devices of satisfactory performance. However, a complete technology requires upgrading of fabrication procedures of all elements of electronic devices and circuits, which not only comprise active layers, but also electrodes, dielectrics, insulators, substrates and protecting/encapsulating coatings. In this review, poly(chloro-para-xylylene) known as Parylene C, which appears to become a versatile supporting material especially suitable for applications in flexible organic electronics, is presented. A synthesis and basic properties of Parylene C are described, followed by several examples of use of parylenes as substrates, dielectrics, insulators, or protecting materials in the construction of organic field-effect transistors.

High-performance single crystal organic field-effect transistors based on two dithiophene-tetrathiafulvalene (DT-TTF) polymorphs.

Solution prepared single crystal organic field-effect transistors (OFETs) combine low-cost with high performance due to structural ordering of molecules. However, in organic crystals polymorphism is a known phenomenon, which can have a crucial influence on charge transport. Here, the performance of solution-prepared single crystal OFETs based on two different polymorphs of dithiophene-tetrathiafulvalene, which were investigated by confocal Raman spectroscopy and X-ray diffraction, are reported. OFET devices prepared using different configurations show that both polymorphs exhibited excellent device performance, although the -phase revealed charge carrier mobility between two and ten times higher in accordance to the closer stacking of the molecules.

Interaction of parylene C with biological objects.

The aim of the present work was to examine the interactions of parylene C with such selected biological objects as: blood plasma proteins, platelets, endothelial cells, and bacterial biofilm produced by E. coli cells. The results obtained strongly support the thesis that parylene C is a material worth considering for biomedical use. Parylene C coating on polished medical steel significantly reduces platelet adhesion to this surface. On the other hand, in the case of the surface of machined medical steel coated with parylene C, the number of adhered platelets is significantly higher. This also means that surface texture of substrate material is very well reproduced by parylene C coating and is an important factor facilitating the platelet adhesion. Adsorption of plasma proteins at parylene C surface is very effective, and this finding confirms a notion that cell interaction with surfaces is mediated by the adsorbed proteins. In the light of the above, a high susceptibility of parylene C surface to bacterial colonization is easy to explain. The results showing reduced proliferation and changes in endothelial cell gene expression should also be seriously analysed when parylene C is considered for the use in contact with blood vessels.