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Herein, a 3D printing technique to enable the manufacturing of selectively plated polymer objects by photopolymer printing and copper metallization is presented. Metallized plastic has become popular in a number of industries due to its lightweight, flexibility of design, and cost‐effective fabrication. Common metallization techniques require multiple pretreatment steps, such as surface etching, sensitization/activation, and acceleration. The proposed method, by eliminating the sensitization step, allows selective metallization of 3D‐printed samples by direct plating. The method relies on the inclusion of silver seeds into a mixture of acrylate‐ and methacrylate‐based monomers and oligomers, which enables direct electroless copper metallization following 3D printing. Ag(I) ions act as catalytic sites for copper deposition. Copper films grown with embedded 2 and 4 wt% Ag(I) seeds reach thicknesses of 5.7 ± 1.2 and 7.7 ± 1.3 μm, respectively. Furthermore, printing with pristine and silver‐modified resins on the same sample allows selective plating: only the modified resin is plated leaving the pristine resin unaffected. A proof‐of‐concept temperature sensor is manufactured to demonstrate the performance of the printed interconnects. [ABSTRACT FROM AUTHOR]

Photopolymer resins used in stereolithographic 3D printing are limited to penetration depths of less than 1 mm. Our approach explores the use of near-infrared (NIR) to visible upconversion (UC) emissions from lanthanide-based phosphors to initiate photopolymer crosslinking at a much higher depth. This concept relies on the use of invisibility windows and non-linear optical effects to achieve selective crosslinking in photopolymers. SLA resin formulation capable of absorbing light in the visible region (420–550 nm) was developed, in order to take advantage of efficient green-UC of Er3+/Yb3+ doped phosphor. NIR-green light UC shows versatility in enhancing curing depths in laser patterning. For instance, a structure with a curing depth of 11 ± 0.2 mm, cured width of 496 ± 5 µm and aspect ratios of over 22.2:1 in a single pass via NIR-green light UC. The penetration depth of the reported formulation approached 39 mm. Therefore, this technique would allow curing depths of up to 4 cm. Moreover, it was also demonstrated that this technique can initiate cross-linking directly at the focal point. This shows the potential of NIR-assisted UC as a low-cost method for direct laser writing in volume and 3D printing. [ABSTRACT FROM AUTHOR]

This article presents a novel waveguide loaded air slots’ resonator (WLASR) comprised of a surrounding metal box and inserted metal disk with etched air slots. The proposed WLASR exhibits a comparable unloaded quality factor ($Q_{\mathrm {u}}$) to the coaxial resonator and allows controlling the electric and magnetic couplings separately. These attractive characteristics were first deployed to design a four-pole inline electrical–magnetic mixed-coupling bandpass filter centered at 2.82 GHz with a fractional bandwidth of 6.73% and two controllable transmission zeros (TZs) located at 2.65 and 2.98 GHz, respectively. Direct metal 3-D printing technology was utilized to manufacture the prototype. The measured results were auspicious for the first demonstrated 3-D printed prototype. Hence, two six-pole filters with multiple TZs, more compact sizes, higher $Q_{\mathrm {u}}$ , and improved shape were designed. For experimental validation, one of them was printed with only two pieces. The measured results agreed well with the simulated ones. [ABSTRACT FROM AUTHOR]

This work presents the synergistic effect of silver (Ag) ions to enhance the crosslinking of 3D printing photopolymers via near-infrared (NIR) to ultraviolet (UV)/visible light upconversion (UC) and allow selective metallization of multi-material parts. By incorporating a commercial micron-sized ytterbium-thulium co-doped sodium yttrium fluoride phosphor (NaYF 4 :Yb3+, Tm3+) into a photopolymer resin, a low-cost NIR laser is used to initiate curing exactly at the focal point in the depth of the vat, allowing voxel crosslinking in any point of the space at a depth in the centimeter scale, beyond the traditional layer-by-layer 2D scheme. This allows the printing with the presented resin on pre-existing printed parts, which is the basis for multi-material integration in 3D printing, beyond the 2D limitation. The addition of Ag(I) ions in the photopolymer enables improved photo-curing at 10-fold faster speeds, after printing through 10 mm of resin. In our approach, after the 3D printing process, the Ag(I) ions embedded into the photopolymer serve as seeding sites for electroless copper (Cu) plating, which allows the integration of metalized parts on different substrates, such as glass and 3D printed polymer. Finally, selective copper plating has enabled the manufacture of objects with metal (copper) and plastic (acrylic) surfaces. [ABSTRACT FROM AUTHOR]