Single-mode, multi-fiber expanded-beam connectors (EBCs) were fabricated based on a two-step process using coreless glass fibers and two-photon polymerization (TTP) 3D printing technique. First, coreless glass fibers were spliced onto a single-mode fiber ribbon and then precisely laser-cleaved to the ideal length. A micro-lens array was directly laser printed onto the coreless fiber extensions using the TPP technique to create the expanded, collimated output beam. Coupling loss measurements at 1310 nm between two 3D-printed EBCs matched the results of simulations. The high spatial resolution of the TPP technique avoids cumbersome active alignment procedures, and thus enables low-cost, high-throughput optical connectivity solutions.
Two-photon polymerization (2PP), a 3D nano to microscale additive manufacturing process, is being used for the first time to fabricate small custom experimental packages (“targets”) to support laser-driven high-energy-density (HED) physics research. Of particular interest is the use of 2PP to deterministically print low-density, low atomic-number (CHO) polymer matrices (“foams”) at millimeter scale with sub-micrometer resolution. Deformation during development and drying of the foam structures remains a challenge when using certain commercial photo-resins; here we compare use of acrylic resins IP-S and IP-Dip. The mechanical strength of polymeric beam and foam structures is examined particularly the degree of deformation that occurs during the development and drying processes. The magnitude of the shrinkage in the two resins in quantified by printing sample structures and by use of FEA to simulate the deformation. Capillary drying forces are shown to be small and likely below the elastic limit of the core foam structure. In contrast the substantial shrinkage in IP-Dip (~5-10%) cause large shear stresses and associated plastic deformation particularly near constrained boundaries such as the substrate and locations with sharp density variation. The inherent weakness of stitching boundaries is also evident and in certain cases can lead to delamination. Use of IP-S shows marked reduction in deformation with a minor loss of print resolution
Low-density foam targets for laser induced shock wave propagation experiments were produced via laser direct writing from polymeric materials. These targets were designed with dimensions of 2.0X0.25X0.3mm with a density of 100mg/cm3 and included a fully polymerized ablation layer, 15μm thick, written contiguously with the low density material in a single fabrication step. We developed a unique protocol in order to assist in the release and harvest of the foam targets from the glass substrate on which they were fabricated. The fabrication process, as well as the assembly and handling of these delicate brittle samples is described in this paper, demonstrating the flexibility, versatility and efficiency of two photon polymerization as fabrication technique that may complement conventional approaches for low density materials fabrication. An ongoing research effort is being conducted in order to reduce to the minimum the content of stitching defects between the target’s building blocks.
Precise assembly of carbon nanotubes (CNTs) in arbitrary 3D space with proper alignment is critically important and desirable for CNT applications but still remains as a long-standing challenge. Using the two-photon polymerization (TPP) technique, it is possible to fabricate 3D micro/nanoscale CNT/polymer architectures with proper CNT alignments in desired directions, which is expected to enable a broad range of applications of CNTs in functional devices. To unleash the full potential of CNTs, it is strategically important to develop TPP-compatible resins with high CNT concentrations for precise assembly of CNTs into 3D micro/nanostructures for functional device applications. We investigated a thiol grafting method in functionalizing multiwalled carbon nanotubes (MWNTs) to develop TPP-compatible MWNT-thiol-acrylate (MTA) composite resins. The composite resins developed had high MWNT concentrations up to 0.2 wt%, over one order of magnitude higher than previously published work. Significantly enhanced electrical and mechanical properties of the 3D micro/nanostructures were achieved. Precisely controlled MWNT assembly and strong anisotropic effects were confirmed. Microelectronic devices made of the MTA composite polymer were demonstrated. The nanofabrication method can achieve controlled assembly of MWNTs in 3D micro/nanostructures, enabling a broad range of CNT applications, including 3D electronics, integrated photonics, and micro/nanoelectromechanical systems (MEMS/NEMS).
Two-photon polymerization (TPP) is of increasing interest due to its unique combination of truly three-dimensional (3D) fabrication capability and ultrahigh spatial resolution of ~40 nm. However, the stringent requirements of non-linear resins seriously limit the material functionality of 3D printing via TPP. Precise fabrication of 3D micro/nanostructures with multi-functionalities such as high electrical conductivity and mechanical strength is still a long-standing challenge. In this work, TPP fabrication of arbitrary 3D micro/nanostructures using multi-walled carbon nanotube (MWNT)-thiolacrylate (MTA) composite resins has been developed. Up to 0.2 wt% MWNTs have been incorporated into thiol-acrylate resins to form highly stable and uniform composite photoresists without obvious degradation for one week at room temperature. Various functional 3D micro/nanostructures including woodpiles, micro-coils, spiral-like photonic crystals, suspended micro-bridges, micro-gears and complex micro-cars have been successfully fabricated. The MTA composite resin offers significant enhancements in electrical conductivity and mechanical strength, and on the same time, preserving high optical transmittance and flexibility. Tightly controlled alignment of MWNTs and the strong anisotropy effect were confirmed. Microelectronic devices including capacitors and resistors made of the MTA composite polymer were demonstrated. The 3D micro/nanofabrication using the MTA composite resins enables the precise 3D printing of micro/nanostructures of high electrical conductivity and mechanical strength, which is expected to lead a wide range of device applications, including micro/nano-electromechanical systems (MEMS/NEMS), integrated photonics and 3D electronics.
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