Two-photon polymerization (TPP) is capable of fabricating 3D structures with dimensions from sub-µm to a few hundred µm. As a direct laser writing (DLW) process, fabrication time of 3D TPP structures scale with the third order, limiting its use in large volume fabrication. Here, we report on a scalable fabrication method that cuts fabrication time to a fraction. A parallelized 9 multi-beamlets DLW process, created by a fixed diffraction optical element (DOE) and subsequent stitching are used to fabricate large periodic high aspect ratio 3D microstructured arrays with sub-micron features spanning several hundred of µm 2. The wall structure in the array is designed with a minimum of traced lines and is created by a low numerical aperture (NA) microscope objective, leading to self-supporting lines omitting the need for line-hatching. The fabricated periodic arrays are applied in a cell-3D microstructure interaction study using living HeLa cells. First indications of increased cell proliferation in the presence of 3D microstructures compared to planar surfaces are obtained. Furthermore, the cells adopt an elongated morphology when attached to the 3D microstructured surfaces. Both results constitute promising findings rendering the 3D microstructures a suited tool for cell interaction experiments, e.g. for cell migration, separation or even tissue engineering studies. 3D fabrication approaches including electro-spinning, nano-imprinting, additive 3D printing of ceramics, metals and plastics together with other forms of bottom-up techniques, have revolutionized tissue and organ engineering, cell migration research and other applications in biomedical research 1-6. Additionally, advanced light-induced material processing techniques have been developed including mask-less and rapid micro-fabrication and-machining, e.g. for surface structuring, ablation and modifications 7-10. Belonging to this class of methods is direct laser writing (DLW) based micro-fabrication, where single-photon DLW can fabricate 2D and 2.5D type structures, while the inherent sectioning capability of multi-photon based DLW allows the fabrication of 3D microstructures 11-14. DLW has shown versatility in the fabrication of high-quality micro-optical elements 12 , waveguides 15 , and micro-machines 16. Laser-based manufacturing is capable of processing bio-compatible materials 17-19. As an optical technique DLW is limited by optical diffraction. Therefore, achievable feature sizes relate to the wavelength of the light source used. The microfabrication resolution furthermore is governed by the material properties, including the polymerization or ablation thresholds. The combination of these two aspects ultimately may allow for fabricating feature sizes well below the optical diffraction limit 20-22. The DLW-based polymerization fabrication process is based on tracing the contours of the structure design in a photosensitive material, followed by a development step to remove the developed/undeveloped polymer to obtain the final microfabricated structure....

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The creation of hole, cavity or channel structures in low-temperature cofired ceramics (LTCCs), using different sacrificial volume materials (SVMs) was tested. The main functionality of the SVMs should be: easy application into the holes; protection of holes during lamination; uninhibited lamination between layers; and, during firing should burn out before the pores of the LTCCs close, to leave the empty holes clear of any residue. Five different materials were tested—hydroxyethyl cellulose (HEC) 2 wt%, HEC 5 wt%, agar-agar, gelatin, and commercial carbon paste—and compared to a reference sample where no SVMs were used. In all cases, lamination parameters were minimised in order to preserve the tested hole structures. Matrixes with holes ranging from 158 to 268 µm, with pitches of 573 µm in a green state, were tested. The agar-agar caused ceramic deformation as a result of thermal burst during firing and the lamination between the layers was compromised. The carbon paste was difficult to handle, requiring extra equipment for hole filling and incomplete filling of the larger holes. Traces of carbon paste were left as a landing pad on top of the holes, inhibiting lamination at these areas. The gelatin and the 2 wt% and 5 wt% hydroxyethylcellulose (HEC 2 wt% and HEC 5 wt%) filled all holes completely, and also worked as adhesive-assisted lamination (AAL) materials with excellent lamination between layers. Excellent lamination was also observed in the no-SVM case. Thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) with energy-dispersive X-ray (EDX) analyses established that, for all SVMs tested, the remaining residue is negligible after firing. As a result, the HEC 2 wt% material was considered ideal for use as an SVM.

This paper reports on the results of the design and manufacturing of straight sections, tees, bends and loads in a Grooved Laminated Waveguide (GLWG) topology. These devices, intended for the U-, V-, W-and G-band, are fabricated in Low Temperature Co-fired Ceramics (LTCC) technology using the low relative permittivity tape, ESL41110, from ElectroScience Laboratory. Measurements ranging from 40 to 170 GHz prove the concept of grooved laminated waveguides.