Origami devices have the ability to spatially reconfigure between 2D and 3D states through folding motions. The precise mapping of origami presents a novel method to spatially tune radio frequency (RF) devices, including adaptive antennas, sensors, reflectors, and frequency selective surfaces (FSSs). While conventional RF FSSs are designed based upon a planar distribution of conductive elements, this leaves the large design space of the out of plane dimension underutilized. We investigated this design regime through the computational study of four FSS origami tessellations with conductive dipoles. The dipole patterns showed increased resonance shift with decreased separation distances, with the separation in the direction orthogonal to the dipole orientations having a more significant effect. The coupling mechanisms between dipole neighbours were evaluated by comparing surface charge densities, which revealed the gain and loss of coupling as the dipoles moved in and out of alignment via folding. Collectively, these results provide a basis of origami FSS designs for experimental study and motivates the development of computational tools to systematically predict optimal fold patterns for targeted frequency response and directionality.
Self-assembled polymer photo-detectors (PPDs) composed of ruthenium complex N3 and PPDs based on thin films of poly(p-phenylene vinlyene) with sulfonated polystyrene are examined for their ability to function in a simulated space radiation environment. Examination of the PPD pre- and post- response data following gamma-ray irradiation ranging in total dose from 10 krad(Si) to 100 krad(Si) are examined. The output photovoltage was observed to decrease for all irradiated devices. The brief study was performed at room temperature and a discussion of the preliminary data and results are presented.
Recently, there has been increased interest in polymer-based photovoltaic devices due to their promise for the creation of lightweight, flexible, and inexpensive electrical power. WE examined the possibility of using nanoparticles and nanoparticles with tailored interfaces for the creation of hybrid polymer-based devices with enhanced photovoltaic response. Initially, we investigated the incorporation of multi-walled carbon nanotubes (MWNT) in the poly(benzimidazo-benzophenanthroline) ladder (BBL) layer of two-layer poly(p-phenylene vinylene)(PPV)-BBL photovoltaic devices. Subsequently, we explored the possibility of tuning polymer-particle interfaces through the creation of core-shell particles fabricated using electrostatic self- assembly. For the PPV/BBL(MWNT) devices, a doubling of the photocurrent and a drastic reduction in photovoltage with MWNT incorporation is observed for a range of BBL layer thickness values. This behavior is consistent with the MWNTs functioning as a three dimensional extension of the top aluminum electrode. Fabrication studies on core-shell particles demonstrate that the interfacial properties of a variety of particles can be manipulated, shells of up to 10 bilayers can be achieved, and TiO2 nanoparticles with PPV polymer shells are possible.
We have recently reported on the fabrication of organic light emitting devices based on sequentially adsorption layers of a polycationic poly(p-phenylene vinylene) (PPV) precursor and poly(methacrylic acid) (PMA). Here we have fabricated devices with PPV precursor and poly(acrylic acid) (PAA) in an effort to further improve device performance by controlling the nature of the polyanion with which the PPV precursor is assembled. We have seen dramatic differences in device performance by systematically varying the bilayer composition and the total film thickness by controlling the solution parameters and the total number of bilayers deposited. In addition, the conversion temperature has also been shown to strongly influence device characteristics. The current, best performing device has been for a system in which the bilayer thickness is around 60 angstrom, approximately half of which is due to the PPV. From this system we have been able to achieve luminance levels greater than 1000 cd/m2 using an aluminum cathode and an ITO anode. Such high brightness levels from a PPV single slab device with an aluminum top electrode are quite unusual.