Inductive grid filters for rejection of infrared radiation

Abstract

Inductive grid filters are metallic mesh structures, which reject long wavelengths but transmit short wavelengths. Our interest is in filters with the rejection cut-off at around 1 μm. In this region the finite conductivity of metals must be considered. An extensive theoretical investigation is carried out by rigorous diffraction theory to determine the best choice of metal and the influence of the grid parameters on the spectral transmittance of the filter. Experimental results with nickel and gold grids fabricated on dielectric substrates are presented. Their fabrication process involves thin-film deposition, electron beam lithography, reactive ion etching and electroplating. The optical characterization results performed with spectrophotometry are in reasonable agreement with the theoretical predictions.     

Preparation and Characterization of Dentin Phosphophoryn‐Derived Peptide‐Functionalized Lignin Nanoparticles for Enhanced Cellular Uptake

The surface modification of nanoparticles (NPs) using different ligands is a common strategy to increase NP?cell interactions. Here, dentin phosphophoryn‐derived peptide (DSS) lignin nanoparticles (LNPs) are prepared and characterized, the cellular internalization of the DSS‐functionalized LNPs (LNPs‐DSS) into three different cancer cell lines is evaluated, and their efficacy with the widely used iRGD peptide is compared. It is shown that controlled extent of carboxylation of lignin improves the stability at physiological conditions of LNPs formed upon solvent exchange. Functionalization with DSS and iRGD peptides maintains the spherical morphology and moderate polydispersity of LNPs. The LNPs exhibit good cytocompatibility when cultured with PC3‐MM2, MDA‐MB‐231, and A549 in the conventional 2D model and in the 3D cell spheroid morphology. Importantly, the 3D cell models reveal augmented internalization of peptide‐functionalized LNPs and improve antiproliferative effects when the LNPs are loaded with a cytotoxic compound. Overall, LNPs‐DSS show equal or even superior cellular internalization than the LNPs‐iRGD, suggesting that DSS can also be used to enhance the cellular uptake of NPs into different types of cells, and release different cargos intracellularly.     

Time integration in linear viscoelasticity—a comparative study

One of the key tasks in computational viscoelasticity is the time integration of the constitutive equation. It is important that the behaviour of the integrators is well understood since they are used in a variety of applications. In the present paper, the performance of conventional semi-analytical methods and implicit Runge-Kutta methods for the integral model of linear viscoelasticity with Prony series is evaluated analytically and numerically. Although a linear viscoelastic constitutive equation is considered, the analyzed integrators can be extended to handle also Schapery-type nonlinear constitutive equations. Numerical examples involving a simple uniaxial problem and multiaxial simulations are presented in order to analyze and compare the time integrators.     

Manufacturing of prestressed piezoelectric unimorphs using a postfired biasing layer

A novel manufacturing method for prestressed piezoelectric unimorphs is introduced and the actuator properties are examined. Prestressed PZT 5A and PZT 5H unimorphs with piezo material thickness of 250 microm and 375 microm were manufactured by using sintering and thermal shrinkage of the prestressing material. The process was carried out by screen printing a layer of AgPd paste on one side of the sintered bulk ceramic. As an alternative method, dielectric low temperature co-fired ceramic (LTCC) tape was used as the prestressing material. Different configurations were tested to obtain high displacements and to make a comparison between materials. After firing, the samples were poled, and the displacement versus load characteristics of the resulting actuators were investigated. A maximum displacement of 118 microm was obtained from a 250 microm thick, prestressed PZT 5H actuator with a diameter of 25 mm, in which LTCC tape was used as the prestressing layer. Similarly, the PZT 5H material provided a maximum displacement of 63 microm with a screen-printed AgPd prestressing layer. The manufacturing method described offers a novel approach for the production of a wide range of integrated active structures on, for instance, an LTCC circuit board. This is especially important because piezoelectric bulk materials with high piezoelectric coefficients can be used to produce high displacements.