Mark S. Mirotznik

The development of electronic substrates from locally available materials is critical for sustainable lunar infrastructure. This work investigates the synthesis, processing, and characterization of cyanate ester–lunar regolith simulant (CE-LRS) composites designed specifically for the extreme lunar environment. LRS were evaluated as functional fillers at loadings up to 55 wt.% with CE binder selected for its thermal stability (T_g > 230 °C), vacuum compatibility, and known radiation resistance from prior literature. A vacuum-assisted curing procedure was developed that utilizes the lunar environment as a processing advantage, reducing porosity from approximately 7% to less than 1% as quantified by X-ray micro-computed tomography. Dynamic mechanical analysis revealed that increased filler loading and vacuum processing enhanced the storage modulus and T_g through constraining polymer chain mobility at the filler-binder interface, confirming effective stress transfer and interfacial adhesion. Scanning electron microscopy also verified intimate polymer–filler wetting. Waveguide measurements in the microwave frequency range demonstrated that the composites remain non-magnetic while exhibiting moderately increased permittivity and low dielectric loss, meeting the requirements for radio-frequency substrate applications. Through material selection and process design that embraces, rather than ignores, lunar environmental constraints, this work establishes the CE-LRS composites that represent a viable pathway for the in situ fabrication of structural electronics on the Moon.

Climate change and the global energy crisis have led to an increasing need for greenhouse gas remediation and clean energy sources. The electrochemical CO₂ reduction reaction (CO₂RR) is a promising solution for both issues as it harvests waste CO₂ and chemically reduces it to more useful forms. However, the high overpotential required for the reaction makes it electrochemically unfavorable. Here, we fabricate a novel electrode composed of TiO₂ nanoparticles grown in situ on MXene charge acceptor 2D sheets with excellent CO₂RR characteristics. A straightforward solvothermal method was used to grow the nanoparticles on the Ti₃C₂T_x MXene flakes. The electrochemical performance of the TiO₂/MXene electrodes was analyzed. The Faradaic efficiencies of the TiO₂/MXene electrodes were determined, with a value of 99.41% at −1.9 V (vs. Ag/AgCl). Density functional theory mechanistic analysis was used to reveal the most likely mechanism resulting in the production of one CO molecule along with a carbonate anion through ∗CO, ∗O, and activated CO₂²⁻ intermediates. Bader charge analysis corroborated this pathway, showing that CO₂ gains a greater negative charge when TiO₂/MXene serves as a catalyst compared to MXene or TiO₂ alone. These results show that TiO₂/MXene nanocomposite electrodes may be very useful in the conversion of CO₂ while still being efficient in both time and cost.

A conformal metasurface antenna exhibiting a pencil beam radiation pattern at 10.0 GHz has been designed using the Voronoi partition approach, and fabricated on the Kahu Uninhabited Aerial System (UAS) fuselage. Two manufacturing methods are presented and compared. The first approach utilized a 3-axis Trotec fiber laser to etch the flattened metasurface geometry in copper foil. The etched pattern was then ‘stretched’ over the UAS geometry. The second approach utilized a 6-axis nScrypt (retrofitted with an IDS aerosol jetting tool) to conformally print the metasurface pattern directly on the UAS fuselage. An electroless copper plating step was then utilized to improve the radiofrequency (RF) conductivity of the printed silver. Both manufacturing methods yielded functional metasurface antennas with equivalent performance at the operating frequency. However, the first method is limited to geometries that can be ‘flattened’ with acceptable tolerances, whereas the second approach is amenable to all practical geometries. This demonstration of two manufacturing techniques is a critical step forward in the cost-effective deployment of truly conformal metasurface antennas on realistic geometries.

Finite Element Analysis (FEA) is used to determine the sensitivity of feed placement on a Luneburg lens (LL) having large scale cubic discretization of its permittivity distribution. This is of practical importance for lenses fabricated using additive manufacturing, allowing accurate prediction of performance, and potentially reducing overall print time. It is shown that the far-field relative side lobe level (RSLL) is most sensitive to this form of discretization, and the impact to multi-feed and single-feed applications is considered. It is shown that for single-feed applications, large cubic macro cells are beneficial and provide a RSLL above that achieved with the continuous and non-uniform shelled counterparts.

In this paper, a new design method is introduced for wideband transitions from an unbalanced coaxial feed to a balanced two wire port. The device expands upon the traditional tapered coaxial balun by allowing for variations of both the inner and outer conductor radii in addition to the slot width. This multi-tapered approach provides additional design freedoms useful for realizing a wide range of impedance ratios, satisfying fixed geometrical constraints, and reducing transmission losses. A multimaterial additive manufacturing (AM) approach is described for fabricating the balun’s complex three-dimensional geometry. Experimental validation was conducted within the Ku-band for printed back-to-back baluns and an integrated antenna feed that combined a printed connector, a multi-tapered coaxial balun, and a spiral antenna. Simulated and measured results showed good performance over the frequency band of interest.

This research applies Effective Medium Theory and 3D Finite Element Analysis to model the transmissive loss through a waveguide fed additively manufactured Luneburg lens. New results are presented that provide rational function approximations for accurately modeling the aperture, beam, and radiation loss factors of the antenna. It introduces a normalized loss tangent and shows that the loss factors are dependent on the product of this parameter and the lens radius. Applying the constraint that the main beam of the radiation pattern contains 50% of accepted power, a maximum useful radius is tabulated for common polymers used in additive manufacturing.

Additively manufactured graded index lenses, such as the Luneburg lens, often result in some degree of uniaxial anisotropy in the effective permittivity distribution. A uniaxially anisotropic Luneburg lens modifies the polarization state of an incident electromagnetic field, thus giving rise to a polarization mismatch at the receiving antenna. Using 3D finite element simulation, the lens focal point polarization is analyzed and a model that fits the simulation data is created. The model allows prediction of polarization mismatch loss given any incident field and any receiving antenna polarization without resorting to further time-consumingsimulations.

We present the design and characterization of fully additively manufactured (AM) SubMiniature version A (SMA) connectors for use up to 18 GHz. Three-dimensional printed connectors can be directly integrated into the radio-frequency (RF) circuit without post-process bonding and can be fabricated into unusual shapes. The flexibility this affords in the manufacturing process offers significant advantages, especially for applications that need to meet strict size and volume constraints. To that end, we describe modifications to the traditional SMA design that better enable AM fabrication. A variety of different connector geometries were printed and fully characterized both electromagnetically and mechanically. Experimental measurements up to 18 GHz demonstrated good RF performance with low insertion losses (< 0.5 dB). Mechanical testing showed that the printed connectors could withstand up to 4.5 kg of direct force for extended periods of time without damage to the printed threads or other connector parts. Additionally, the printed connectors demonstrated good RF performance after repeated use.

We demonstrate a new method for realizing Luneburg lens antennas with nearly continuously graded permittivity profiles in three dimensions. The method combines fused filament fabrication, a nearly ubiquitous additive manufacturing technique, with an effective media approach that employs space-filling curves. We experimentally validate our design methodology by fabricating and characterizing two Luneburg lenses designed to operate at separate frequency bands (26–40 GHz and 70–110 GHz) with antenna gains of 20 and 24 dBi, respectively. The results demonstrate good agreement with rigorous electromagnetic simulations. We also demonstrate the ability to passively beam steer over a wideband of operation (26–40 GHz and 70–110 GHz) with less than 0.5% power loss due to dielectric material losses within the Luneburg lens.

The ability to fabricate multifunctional devices that combine good structural properties with embedded electromagnetic functionality has many practical applications, including antireflective surfaces for structural radomes, load bearing conformal antennas, integrated RF transmission lines and passive beam forming networks. We describe here a custom made 3D printer that can print high dielectric constant ceramic powders within a low-loss structural composite substrate to produce mechanically robust parts with integrated graded dielectric properties. We fabricated a number of these parts and evaluated their anisotropic dielectric properties by determining the complete permittivity tensor of the printed samples as a function of local powder weight. This data was then experimentally validated using two practical examples: a Chebyshev antireflective stack and a 2D passive beamsteering network. The results of both electromagnetic systems displayed acceptable agreement between the simulated and measured results. This agreement shows that powder printing is a potential approach for fabricating spatially graded dielectric electromagnetic systems.