Optically Transparent Tri-Wideband Mosaic Frequency Selective Surface with Low Cross-Polarisation

Acquiring an optically transparent feature on the wideband frequency selective surface (FSS), particularly for smart city applications (building window and transportation services) and vehicle windows, is a challenging task. Hence, this study assessed the performance of optically transparent mosaic frequency selective surfaces (MFSS) with a conductive metallic element unit cell that integrated Koch fractal and double hexagonal loop fabricated on a polycarbonate substrate. The opaque and transparent features of the MFSS were studied. While the study on opaque MFSS revealed the advantage of having wideband responses, the study on transparent MFSS was performed to determine the optical transparency application with wideband feature. To comprehend the MFSS design, the evolutionary influence of the unit cell on the performance of MFSS was investigated and discussed thoroughly in this paper. Both the opaque and transparent MFSS yielded wideband bandstop and bandpass responses with low cross-polarisation (−37 dB), whereas the angular stability was limited to only 25°. The transparent MFSS displayed high-level transparency exceeding 70%. Both the simulated and measured performance comparison exhibited good correlation for both opaque and transparent MFSS. The proposed transparent MFSS with wideband frequency response and low cross-polarisation features signified a promising filtering potential in multiple applications.

Nanoplasmonic Structure of a Polycarbonate Substrate Integrated with Parallel Microchannels for Label-Free Multiplex Detection

In this study, a multiplex detection system was proposed by integrating a localized surface plasmon resonance (LSPR) sensing array and parallel microfluidic channels. The LSPR sensing array was fabricated by nanoimprinting and gold sputter on a polycarbonate (PC) substrate. The polydimethylsiloxane (PDMS) microfluidic channels and PC LSPR sensing array were bound together through (3-aminopropyl)triethoxysilane (APTES) surface treatment and oxygen plasma treatment. The resonant spectrum of the LSPR sensing device was obtained by broadband white-light illumination and polarized wavelength measurements with a spectrometer. The sensitivity of the LSPR sensing device was measured using various ratios of glycerol to water solutions with different refractive indices. Multiplex detection was demonstrated using human immunoglobulin G (IgG), IgA, and IgM. The anti-IgG, anti-IgA, and anti-IgM were separately modified in each sensing region. Various concentrations of human IgG, IgA, and IgM were prepared to prove the concept that the parallel sensing device can be used to detect different targets.

Comparative Evaluation of Cu(acac)2 and {[Cu(μ-O,O′-NO3) (L-arg) (2,2′-bpy)]·NO3}n as Potential Precursors of Electroless Metallization of Laser-Activated Polymer Materials

This paper presents a comparative assessment of Cu(acac)2 and {[Cu(μ-O,O′-NO3) (L-arg)(2,2′-bpy)]·NO3}n as potential precursors for the electroless metallization of laser activated polymer materials. Coatings consisting of polyurethane resin, one of the two mentioned precursor compounds, and antimony oxide (Sb2O3), as a compound strongly absorbing infrared radiation, were applied on the polycarbonate substrate. The coatings were activated with infrared Nd: YAG laser radiation (λ = 1064 nm) and electroless metallized. It was found that after laser irradiation, a micro-rough surface structure of the coatings was formed, on which copper was present in various oxidation states, as well as in its metallic form. For selected parameters of laser irradiation, it was possible to deposit a copper layer on the coating containing Cu(acac)2 and Sb2O3, which is characterized by high adhesion strength. It was also found that the {[Cu(μ-O,O′-NO3) (L-arg)(2,2′-bpy)]·NO3}n complex was not an effective precursor for the electroless metallization of Nd:YAG laser activated coatings. An attempt was made to determine the influence of the precursor chemical structure on the obtained metallization effects.

Passive Adaptive Wave Manipulation Using Nonlinear Acoustic Metamaterials

Acoustic metamaterials display unusual mechanical wave manipulation behavior not seen in natural materials. In this study, nonlinear metamaterials with passive, amplitude-activated directional bandgaps are investigated. Test articles are constructed by installing periodic arrays of mass-loaded dome resonators on a square polycarbonate substrate. These resonators display nonlinear softening response with increase in excitation amplitude. Experiments conducted by mounting the test articles on low-stiffness boundaries along two adjacent sides and applying mechanical excitations at the opposite corner. A mechanically-staged laser vibrometer mounted overhead was used to make noncontact measurements at discrete plate and resonator locations. Measured displacement transmissibility verify the existence and extent of bandgap frequency ranges as well as amplitude-activated shifts in their bounds. Moreover, by tailoring the pattern of resonators within the array, preferential steering, focusing and selective beaming of waves within tunable frequency ranges depending on their amplitude are shown to be possible. Steady-state spatial maps depicting the displacement transmissibility field were generated from experiments and correlated with simulations to bring out underlying mechanisms. In addition, both lumped parameter and continuum models are considered to aid the design of scalable, passive adaptive metamaterial waveguides for applications ranging from seismic wave mitigation to MEMS transduction.