Joachim H. G. Steinke

High performance organic semiconducting thin films: Ink jet printed polythiophene [rr-P3HT]

Abstract The piezoelectric ink jet (IJ) printing of an organic semiconducting ink, as applied to the fabrication of a thin film diode, has been demonstrated. IJ printed regioregular poly (3-hexylthiophene-2,5-diyl) [ rr -P3HT] semiconducting films were directly patterned on to gold thin film contact surfaces. The resulting metal–semiconductor–metal diode exhibited low leakage current and a good forward–reverse current ratio. IJ printing of the P3HT as directly patterned thin films represents a significant step toward the realisation of cheap, large area, organic microelectronic devices and transistor active matrix backplanes.

The imitation game - A computational chemical approach to recognizing life

When is an artificial cell alive? A Turing test–like method may provide the answer.

Patterned low temperature copper-rich deposits using inkjet printing

A PZT piezoelectric ceramic research drop-on-demand inkjet print head operating in bend mode was used as a means of delivering a copper precursor, vinyltrimethylsilane copper (+1) hexafluoroacetylacetonate, in a controlled and placement accurate fashion. The reagent disproportionates at low temperature (<200 °C), to deposit copper on glass. These deposits are shown to be more than 90% copper by weight by electron probe microanalysis and microbeam Rutherford backscattering spectroscopy. Microscopy shows a deposit diameter and three-dimensional profile that suggests a complex deposition and conversion mechanism. Our findings represent an important step towards the manufacture of electronic devices by entirely nonlithographic means.

Interconnected macroporous glycidyl methacrylate-grafted dextran hydrogels synthesised from hydroxyapatite nanoparticle stabilised high internal phase emulsion templates

Commercially available hydroxyapatite (HAp) nanoparticles were used as sole emulsifiers to produce stable methyl myristate-in-water and soybean oil-in-water high internal phase emulsions (HIPEs). The droplet size in the Pickering inverse HIPEs (i-HIPEs) could be adjusted within a certain range by tailoring the energy input during emulsification and emulsifier concentrations. These HAp nanoparticle stabilised i-HIPEs were then used as templates to synthesise interconnected high porosity macroporous hydrogels by crosslinking glycidyl methacrylate (GMA) functionalised dextran, which was dissolved in the continuous aqueous phase of the i-HIPEs. The pore size of these polyPickering-HIPE hydrogels could be adjusted by the emulsifier concentration, oil type, emulsification conditions or ripening time of the i-HIPE templates.

Ion-responsive alginate based macroporous injectable hydrogel scaffolds prepared by emulsion templating

Ion-responsive biocompatible macroporous hydrogels with a well-defined highly interconnected open porous structure were synthesised using oil-in-water (o/w) high internal phase emulsion (HIPE) templating. Methacrylate-modified alginate was crosslinked in the continuous minority water phase and the oil internal phase removed to produce macroporous hydrogel monoliths. The physical dimensions, pore and pore throat size as well as water uptake of the alginate polyHIPE hydrogel can be controllably tuned by ion-responsive behaviour towards Ca2+ ions. The ionic crosslinks formed are fully reversible and be dissolved using sodium citrate to remove Ca2+ ions through chelation. The polyHIPE hydrogels possess mechanical properties with storage moduli up to 20 kPa and are biocompatible as shown by cytotoxicity assays. The hydrogel can be extruded through a hypodermic needle causing it to break into small pieces (about 1 to 3 mm in diameter) while retaining the interconnected pore morphology after injection. Furthermore, these hydrogel fragments can be reformed into a coherent scaffold under mild conditions using an alginate solution containing Ca2+ ions.

Catalytically self-threading polyrotaxanes

A mainchain polyrotaxane is formed in which polymerisation and rotaxane formation occur simultaneously, due to the presence of the catalytically-active self-threading macrocycle cucurbituril.

High-performance flexible bottom-gate organic field-effect transistors with gravure printed thin organic dielectric

One of the key advantages of organic field-effect transistors (OFETs) is their ability to form flexible, conformable and lightweight electronic devices, e.g. radio frequency identification (RFID) tags,[1] microprocessors[2] and flexible displays.[3] These require fabrication over large-areas on flexible plastic substrates, the poor dimensional stability of such substrates creating the additional demand of low-temperature processing (<200 °C).[4] While high performance source, drain and gate electrodes and interconnects require metal evaporation under vacuum, ideally the dielectric and organic semiconductor (OSC) should be processed from solution under ambient conditions to reduce fabrication costs. Regarding device architecture, OFETs with a bottom-gate (BG) bottom-contact (BC) geometry (Figure ​1c)1c) have an advantage in that the organic semiconducting layer is deposited last.[5] This affords easy fabrication and patterning of micron-scale OFET channels, electrodes and interconnects by conventional photolithographic methods, whilst avoiding exposure of the active OSC material to UV radiation and aggressive or solubilising chemicals. Furthermore, this architecture is compatible with vacuum sublimation or vapour phase techniques for OSC deposition, allowing access to a wide range of high-performance materials. Such OFETs can form the building blocks of high performance, low-cost electronic circuitry.

Ionic Liquids as Internal Phase for Non‐Aqueous PolyHIPEs

Stable high internal phase emulsions (HIPEs) with the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)imide as dispersed phase were prepared and polymerised thermally into polyHIPEs. All polyHIPEs exhibited pore morphologies similar to that of polyHIPEs obtained with an aqueous dispersed phase. PolyHIPEs containing the dispersed phase possess a low T(g) and are thermally stable in excess of 200 °C, offering the potential for new porous materials where water as dispersed phase is chemically or physically undesirable.

Bioresponsive Small Molecule Polyamines as Noncytotoxic Alternative to Polyethylenimine

Nonviral gene therapy continues to require novel synthetic vectors to deliver therapeutic nucleic acids effectively and safely. The majority of synthetic nonviral vectors employed in clinical trials to date have been cationic liposomes; however, cationic polymers are attracting increasing attention. One of the few cationic polymers to enter clinical trials has been polyethylenimine (PEI); however, doubts remain over its cytotoxicity, and in addition it displays lower levels of transfection than viral systems. Herein, we report on the development of a series of small molecule analogues of PEI that are bioresponsive to the presence of pDNA, forming poly(disulfide)s that are capable of efficacious transfection with no associated toxicity. The most effective small molecule developed, a cyclic disulfide based upon a spermine backbone, is shown to form very well-defined polyplexes (100-200 nm in diameter) that mediate murine lung transfection in vivo to within an order of magnitude of in vivo jetPEI, and at the same time display a much improved cytotoxicity profile.

Formation of oligotriazoles catalysed by cucurbituril

The catalytic activity of cucurbituril in 1,3-dipolar cycloadditions has been applied to the synthesis of oligotriazoles.