In this paper, the development of an all 3-D printed wide band (2-18 GHz) free-space measurement system for characterizing the complex dielectric properties of flexible as well as rigid materials was demonstrated. Each part of the setup was designed and simulated precisely to show the effect of the 3-D printed quasi-optical lenses placed in front of the wide band ridged horn antennas on the beam and radiation pattern. More than 10 parts of the setup were 3-D printed using two different 3-D printers, and the parts were assembled together with precise alignment. The method used to analytically extract the dielectric properties was explained in detail, and the analytical S-parameters were compared with experimental S-parameters for various plastic materials to verify the measurement system. Four types of commercially available materials: polyimide film (Kapton), liquid crystalline polymer sheet (LCP), ceramic-filled polytetrafluoroethylene composites (RO3035), and polypropylene with different thicknesses were characterized, and obtained dielectric constant and loss tangent values were compared with the data available from the vendors.

We demonstrate a new fully printed, conformal, band-pass frequency selective surface (FSS) utilizing a novel interdigitated capacitor (IDC), in which the space between the fingers can be filled with dielectric materials with different dielectric constants. Every dielectric constant corresponds to a different resonance frequency for the FSS, leading to a bandpass performance that can be tuned in a static manner based on the dielectric choice. The 2-D FSS consists of a periodic array of non-resonant and subwavelength structures (i.e., a metallic square loop and a wire grid) printed on either side of a flexible polyimide film using direct-ink writing methodologies. The miniaturized-element nature of this metamaterial-inspired FSS results in localized frequency-selective properties with very low sensitivity to the angle of incidence. Moreover, its symmetric design makes it polarization independent. A multiphase barium strontium titanate/cyclic olefin copolymer (BST/COC) composite with two different BST loadings, corresponding to two different dielectric constants, is the dielectric ink that is printed on the IDCs to vary the resonance frequency of the FSS. Different models of the FSS involving various IDC designs, with a first-order bandpass response at X-band, were simulated, printed, and measured. The center frequency of the template FSS with the air-filled IDC was tuned by 4.52% and 21.08% from 9.96 GHz by printing BST/COC dielectrics with different BST loadings on the IDCs. Moreover, the operation mode of the FSS was switched from a first order filter to a dual-band filter using printed BST/COC ink in a novel FSS design.

In this letter, an absorber design is introduced that has a very wide absorption band at normal incidence over the midrange infrared (IR) wavelength regime. The proposed structure is comprises four layers, where the extra layer adds a degree of freedom in optimizing the response compared the conventional three-layered absorbers (dielectric spacer sandwiched between a ground thin film and a resonant conducting pattern). The simulations revealed a broadband absorption region that extends from 3 up to 12 μm of light wavelength achieving more than 120% of full bandwidth at half-maximum (FWHM).

In this article, we report the development of a new method for the 3D printing of dielectrics. An aerosol-jet printer is used to deposit overlapping layers of photopolymer material under ultraviolet floodlight in the assembly of ramping microstructures in situ without the need for supporting structures. Printing is conducted using an in-house photodielectric ink, the development of which is presented with an emphasis on dielectric and mechanical bulk material characterization. Low dielectric loss at the X-band and structural strength are demonstrated, followed by print characterization wherein the driving mechanisms of the new method are explored, tied to print conditions, and related to specific material properties. Finally, a complex structure in the form of a 3D flower is printed to demonstrate the controlled and repeatable performance of the proposed technique.