Flexible
pressure sensors are an attractive area of research due
to their potential applications in biomedical sensing and wearable
devices. Among flexible and wearable pressure sensors, capacitive
pressure sensors show significant advantages, owing to their potential
low cost, ultralow power consumption, tolerance to temperature variations,
high sensitivity, and low hysteresis. In this work, we develop capacitive
flexible pressure sensors using graphene based conductive foams. In
these soft and porous conductive foams, graphene is present either
as a coating of the pores in the foam, inside the structure of the
foam, or as a combination of both. We demonstrate that they are durable
and sensitive at low pressure ranges (<10 kPa). Systematic analysis
of the different pressure sensors revealed that the porous foams with
graphene coated pores are the most sensitive (∼0.137 kPa–1) in the pressure range 0–6 kPa, with a limit
of detection of 50 Pa. Further, we demonstrated the potential applications
of our pressure sensors by showing detection of weak physiological
signals of the body. Our work is highly relevant for research in flexible
pressure sensors based on conductive foams as it shows the impact
of different ways of incorporating conductive material on performance
of pressure sensors.
Herein, we compare a series of solution-processible TADF polymers with different host pendant groups to achieve balanced charge transport properties through the combination of unipolar co-hosts.
Organic thin film transistors, employing diverse device architectures, materials and form factors, have been demonstrated as effective sensors of a variety of analytes, including ions. In many such devices, it...
We introduce a catalyst-free, highly efficient, ambient temperature Diels−Alder reaction employing omethylbenzaldehyde derivatives as photocaged dienes as an ideal approach for forming three-dimensional insoluble networks for inkjet printing of OLED emissive layer. Herein, poly(methyl methacrylate) based polymers containing 4-(9H-carbazol-9-yl)-2-(3′-hydroxy-[1,1′-biphenyl]-3-yl)isoindoline-1,3-dione as a blue-green (λ max = 495−500 nm) thermally activated delayed fluorescence (TADF) emitter and a photochemically active maleimide/o-methylbenzaldehyde cross-linker couple were synthesized and their photo-cross-linking behavior was studied. Time resolved fluorescence measurements confirm that the TADF properties are maintained upon integration in a polymer network and HOMO/LUMO levels of the emitter species remain unchanged by the photo-cross-linking at 365 nm of the polymer chains. The network formation of the fluorescent films is evidenced by solvent resistance tests and monitored by Fourier transform infrared (FT-IR) spectroscopy as well as time of flight secondary ion mass spectroscopy (ToF-SIMS), showing the consumption of maleimide and o-methylbenzaldehyde groups with increasing irradiation time. The surface roughness is investigated via atomic force microscopy (AFM) and found to be unchanged by a solvent wash after the cross-linking. Furthermore, confirmation that the polymer solution can be printed on an inkjet-printer and subsequently photo-cross-linked for multilayer OLED device fabrication is obtained.
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