A substrateless, flexible, and water-resistant organic light-emitting diode.

Despite widespread interest, ultrathin and highly flexible light-emitting devices that can be seamlessly integrated and used for flexible displays, wearables, and as bioimplants remain elusive. Organic light-emitting diodes (OLEDs) with µm-scale thickness and exceptional flexibility have been demonstrated but show insufficient stability in air and moist environments due to a lack of suitable encapsulation barriers. Here, we demonstrate an efficient and stable OLED with a total thickness of ≈ 12 µm that can be fully immersed in water or cell nutrient media for weeks without suffering substantial degradation. The active layers of the device are embedded between conformal barriers formed by alternating layers of parylene-C and metal oxides that are deposited through a low temperature chemical vapour process. These barriers also confer stability of the OLED to repeated bending and to extensive postprocessing, e.g. via reactive gas plasmas, organic solvents, and photolithography. This unprecedented robustness opens up a wide range of novel possibilities for ultrathin OLEDs.

Fast Delayed Emission in New Pyridazine-Based Compounds.

Three novel donor-acceptor molecules comprising the underexplored pyridazine (Pydz) acceptor moiety have been synthesized and their structural, electrochemical and photophysical properties thoroughly characterized. Combining Pydz with two phenoxazine donor units linked via a phenyl bridge in a meta configuration (dPXZMePydz) leads to high reverse intersystem crossing rate k RISC = 3.9 · 106 s-1 and fast thermally activated delayed fluorescence (TADF) with <500 ns delayed emission lifetime. Efficient triplet harvesting via the TADF mechanism is demonstrated in OLEDs using dPXZMePydz as the emitter but does not occur for compounds bearing weaker donor units.

Narrowband Organic Light-Emitting Diodes for Fluorescence Microscopy and Calcium Imaging.

Fluorescence imaging is an indispensable tool in biology, with applications ranging from single-cell to whole-animal studies and with live mapping of neuronal activity currently receiving particular attention. To enable fluorescence imaging at cellular scale in freely moving animals, miniaturized microscopes and lensless imagers are developed that can be implanted in a minimally invasive fashion; but the rigidity, size, and potential toxicity of the involved light sources remain a challenge. Here, narrowband organic light-emitting diodes (OLEDs) are developed and used for fluorescence imaging of live cells and for mapping of neuronal activity in Drosophila melanogaster via genetically encoded Ca2+ indicators. In order to avoid spectral overlap with fluorescence from the sample, distributed Bragg reflectors are integrated onto the OLEDs to block their long-wavelength emission tail, which enables an image contrast comparable to conventional, much bulkier mercury light sources. As OLEDs can be fabricated on mechanically flexible substrates and structured into arrays of cell-sized pixels, this work opens a new pathway for the development of implantable light sources that enable functional imaging and sensing in freely moving animals.

Analysis and interpretation of mixed profiles generated by 34 cycle SGM Plus(®) amplification.

Interpretation rules for standard 28 cycle PCR have been described previously for the analysis of mixed STR profiles. In this study the same guidelines are applied to 200 mixtures derived from pairs of known donors combined in ratios of 1:1, 2:1 and 5:1 which have been profiled in duplicate with SGM Plus(®) at total inputs ranging from 1ng to 50pg. The paired profiles were distributed among 35 FSS (Forensic Science Service) reporting officers trained in low copy number (LCN) interpretation who analysed them blind following standard casework procedures. Based upon the results from initial duplicate 34 cycle PCR reactions, the reporting officers made appropriate decisions regarding the benefits of processing the reserved third aliquot. Using the combined results, 49 consensus profiles were successfully resolved into major and minor contributor peaks. This demonstrates the reliability of the interpretation rules used in standard 28 cycle SGM Plus analysis when applied to 34 cycle generated profiles by trained and experienced reporting officers. No minor contributor peaks were assigned to a major profile in the final reported results. Those profiles which did not show sufficiently marked and consistent differentiation into major and minor peaks would have been correctly resolved if the profile of one contributor (e.g. the "victim") was known.

Validation of a dual cycle ethylene oxide treatment technique to remove DNA from consumables used in forensic laboratories.

Validation of a dual cycle ethylene oxide (EO) approach to removing DNA contamination from consumables has been undertaken. The limits of the technique were investigated resulting in evidence that the DNA from up to 50microl of blood and saliva can be removed to a level where the consumable can be considered DNA free. DNA from semen was more resilient and some allelic peaks remained that would have prevented the consumable being classed as suitable for use in low template DNA analysis. No residual effect on consumables resulting in inhibition of subsequent DNA analysis was noted. However, if consumables had been previously treated with gamma or electron beam irradiation then slight inhibition of the downstream STR process was observed. Dual cycle EO treatment was effective at removing recoverable DNA from swabs and stain cards and consideration should be given to the suitability of EO treatment for use on critical consumables used in the forensic laboratory.