A research collaboration between the University of California at Berkeley, the University of California, Los Angeles (UCLA), and Lawrence Berkeley National Laboratory (LBNL) has led to the development of a charge-programmed deposition method for 3D printing ultralight, high-frequency antennas. The study, published in Nature Communications, demonstrates a fabrication process that integrates conductive and dielectric materials without substrates or sintering. Tested at 19 GHz, the antennas include circularly polarized transmitarrays and a monolithic horn feed with internal waveguide structures. A 12 cm transmitarray fabricated using this method weighed 5 grams—over 90% lighter than a conventionally manufactured equivalent.
CPD is based on stereolithography combined with charge-guided material deposition. By assigning electrostatic polarities to photo-curable resins, engineers controlled where metal ions would attach during electroless plating. This allowed precise, substrate-free printing of interpenetrating dielectric and metallic features without relying on post-sintering or mechanical assembly. Measurements conducted at UCLA’s spherical near-field range confirmed that printed antennas performed within 0.8 dB of simulation results.
Fabrication process begins by patterning dielectric phases with prescribed surface charges using projection stereolithography. By formulating photoresins with positive, negative, or neutral charge characteristics, researchers were able to dictate material behavior during subsequent deposition steps. Copper plating occurred selectively in regions with opposite charge polarity, eliminating the need for direct writing, substrates, or high-temperature sintering.
Copper was deposited with a conductivity of 4.9 × 10⁷ S/m, verified through scanning electron microscopy and atomic force microscopy. Resolution reached 18 micrometers, determined by the pixel size of the light projection system. No cracking or delamination was observed across multiple test structures. Compared to traditional methods that require multiple fabrication stages, CPD reduced production to a single-print operation with minimal post-processing.
Antennas fabricated with high-resolution features and varied materials
The researchers produced several antenna types using CPD, including transmitarrays, Vivaldi antennas, folded electrically small antennas, and horn structures. These devices incorporated interlocking dielectric and copper elements that were directly printed in three dimensions. For instance, a gradient-phase transmitarray featured three layers of S-ring unit cells with structural air gaps. Copper rings were embedded in dielectric supports without excess substrate, reducing electromagnetic interference and physical mass.
Material compatibility extended beyond standard resins. Polyimide, epoxy thermosets, elastomers, and ceramic composites were all adapted for CPD use. Each formulation was modified to include charged monomers, enabling selective plating. A patch antenna using liquid metal eutectic gallium-indium (EGaIn) was fabricated by plating copper onto an elastomeric resin and applying EGaIn as the conductive interface. Another example involved printing a GPS antenna using a lead zirconate titanate ceramic that withstood sintering at 1000°C, followed by surface reduction at 300°C.
Performance across these devices remained consistent. Polyimide substrates, processed from polyamic acid precursors, showed a Young’s modulus of 2.4 GPa and retained stability from cryogenic temperatures to above 400°C. Copper patterns printed on these materials maintained structural adhesion and electrical performance through post-curing and handling. Liquid metal antennas retained stretchability and were measured under deformation, showing no loss of continuity in conductive paths.
A 12 cm transmitarray designed with CPD used three discrete copper S-ring elements per unit cell. These rings were embedded in a dielectric skeleton with minimized volume, maintaining air gaps to reduce weight and enable broadband phase control. Rotation of each ring introduced local phase shifts to flatten the incoming spherical wavefront from the source horn antenna.
That horn antenna, also fabricated via CPD, included a WR-42 standard interface, a square-to-circular adapter, and an internal septum polarizer constructed from a single print. Copper was deposited only along interior electromagnetic paths, avoiding full-thickness solid metal bodies. Simulation and measurement showed a directivity of 15.4 dBi at 19 GHz, with an axial ratio of 0.1 dB and a gain loss of 1.6 dB due to ohmic and dielectric losses.
Combined testing of the horn and transmitarray produced a total system directivity of 24.1 dBi. A second 12 cm transmitarray was fabricated using four tiled quadrants, aligned with snap-fit connectors and measured under identical conditions. Directivity dropped by only 0.2 dB, confirming that the tiling process preserved aperture integrity. Beamwidth variation remained within 0.3 degrees.
Scalability achieved through modular construction and tiling
To overcome the build-area constraints of desktop stereolithography systems—typically limited to under 10 cm—researchers implemented a modular tiling strategy. A 20 cm transmitarray was assembled from four individually printed quadrants and mounted using a frame to ensure mechanical alignment. This structure, too large to fabricate in a single print, was tested using the same horn antenna as a feed source.
At 19 GHz, the 20 cm tiled transmitarray demonstrated a measured directivity of 28.3 dBi, closely matching the 29.1 dBi predicted in simulation. Axial ratio remained below 2 dB across a 1 GHz bandwidth. Radiation pattern symmetry and gain stability confirmed that modular construction had minimal impact on electromagnetic performance. Total mass of the assembled array remained below 20 grams, compared to approximately 160 grams for an equivalent PCB-based version.
Researchers extended the CPD process to fabricate a gradient-phase transmitarray (GPTA) for use in a Risley prism antenna (RPA) configuration. This antenna system uses mechanical rotation of stacked GPTA and feed panels to steer the beam without electronic phase shifters. The GPTA panel reused the three-layer S-ring structure developed for previous transmitarrays.
Measurements at UCLA showed beam angles ranging from 0° to 60°, controlled by physical rotation of the GPTA. Total mass of the 20 cm GPTA, including the test mount, was 28 grams. A comparable laminate-based panel would weigh over 60 grams. Measured patterns aligned with simulation predictions across all steering angles, and no structural damage occurred during rotation cycles.
All components fabricated using commercial desktop system
All antenna elements were produced using the Anycubic Photon Mono X stereolithography printer. Resin exchange was performed manually between charged and neutral phases. Printing time for a typical 12 cm transmitarray was under two hours, followed by copper plating completed in less than one day. No sintering, machining, or toolpath generation was required. Alignment for multi-material prints was maintained by keeping the build platform stationary during resin changes.
The electroless deposition process used commercially available copper plating solutions, preceded by selective palladium nanoparticle activation and reducing steps. Copper layers were deposited up to desired thickness without exceeding 2 hours, avoiding surface cracking. SEM analysis confirmed conformal coverage, especially in recessed or narrow dielectric features.
Each antenna system was tested individually in a near-field chamber, then re-tested as part of an integrated assembly. Differences in directivity, polarization, or return loss remained within experimental uncertainty.
Charge-programmed deposition enables direct 3D printing of antennas with structural and electromagnetic characteristics previously unachievable by traditional manufacturing methods. Multi-layer devices with embedded conductive paths were fabricated in a single workflow, reducing weight by over 90% and enabling new form factors. Mechanical tiling allowed aperture scaling without performance degradation. Compatibility with polymers, ceramics, elastomers, and liquid metals further expands the range of antenna types that can be produced.
All fabrication steps were completed using a commercial desktop SLA printer and standard electroless copper solutions. No specialized machinery or post-processing infrastructure was required.
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Featured image shows 3D printed antenna systems. Image via Nature Communications.
