Recently, 3D imaging endoscopes have made their way into endoscopy and enable three-dimensional visualization. While many of them require optics with mounts increasing the fibers diameter, two-photon polymerization enables mount-free fabrication of optical elements directly on the tip of fibers. Using multicore fibers combined with diffractive optical elements (DOE) enables the phase to be taken into account in measurements in addition to intensity, enabling 3D imaging. While each multicore fiber has an individual distribution of phase differences, an individual DOE is required, which can be fabricated rapidly and stitching-free with high precision using maskless 3D lithography.
KEYWORDS: 3D printing, Lithography, Two photon polymerization, Manufacturing, Ultraviolet radiation, Surface roughness, Printing, Laser systems engineering, Cartilage, Bone
Based on the underlying printing resolution Two-Photon Polymerization (TPP) can be distinguished into 3D Lithography and Micro 3D Printing applications. Both of these fields will be discussed in terms of the requirements on the fabrication process such as exposure strategy, overall resolution and accessible print height among others. Enabling both 3D Lithography and Micro 3D Printing in one TPP laser system imposes certain challenges which will be addressed with solutions being presented.
Recently, 3D imaging endoscopes have made their way into endoscopy and enable three-dimensional visualization. While many of them require optics with mounts increasing the fibers diameter, two-photon polymerization enables mount-free fabrication of optical elements directly on the tip of fibers. Using multicore fibers combined with diffractive optical elements (DOE) enables the phase to be taken into account in measurements in addition to intensity, enabling 3D imaging. While each multicore fiber has an individual distribution of phase differences, an individual DOE is required, which can be fabricated rapidly and stitching-free with high precision using maskless 3D lithography.
Industrial High Precision 3D Lithography via Two-Photon Absorption (TPA) is a potential disruptive tool for microfabrication that enables novel products for diverse applications in the field of optics, photonics, biomedicine, and life sciences. A customized therapeutic approach to develop bone cartilage transplants for patients with arthrosis by means of TPA is presented. These implants consist of scaffolds as extracellular matrices (ECM) that mimic natural tissue and serve as physical and bioactive support for the generation of autologous tissue capable of replacing or repairing damaged tissue. The variable TPA technology with adjustable precision and structure dimension is the key to a defined micro structuring that enables hierarchically 3D micro structured monolithic biphasic scaffolds for the therapy of bone cartilage damage on an industrial scale.
The use of two-photon absorption (TPA) for polymerization, also known as 3D Lithography, Direct Laser Writing, or High-Precision 3D Printing is gaining increasing attraction in industrial fabrication of micro- and nanostructures. Mainly due to its vast freedom in design and high-resolution capabilities, TPA enables the fabrication of designs which are not feasible or far too complicated to be achieved with conventional fabrication methods. TPA is a scanning technology and fabrication in 3D requires axial overwritings. High industrial throughput fabrication can be achieved by intelligent fabrication strategies combined with an excellent material basis. Further boosting the throughput can be achieved by multispot exposure strategies. In this paper, massive parallelization is demonstrated which was realized by using a beam splitting diffractive optical element (DOE). Simultaneous fabrication using commercially available acrylate-based hybrid resin with 121 parallel focal spots arranged as 11 x 11 array is reported. Structures fabricated by a single laser beam and by 121 parallel beams are compared to each other with regard to shape and polymerization threshold. It was found that polymerization is strongly increased when parallel beams are used, especially for the central beams. As a result, polymerization threshold is lower in the center of the 11 x 11 array compared to the edges of the array. Furthermore, structures at the center of the 11 x 11 array are bigger compared to structures at the edges of the array when assigning equal intensity to all diffracted beams. These results are attributed to diffusion of photo initiators, quenchers, and radicals.
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