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....

The optical properties of diatom silicate frustules inspire photonics and nanotechnology research. Whether light interaction with the nano-structure of the frustule also affects diatom photosynthesis has remained unclear due to lack of information on frustule optical properties under more natural conditions. Here we demonstrate that the optical properties of the frustule valves in water affect light harvesting and photosynthesis in live cells of centric diatoms (Coscinodiscus granii). Microscale cellular mapping of photosynthesis around localized spot illumination demonstrated optical coupling of chloroplasts to the valve wall. Photonic structures of the three-layered C. granii valve facilitated light redistribution and efficient photosynthesis in cell regions distant from the directly illuminated area. The different porous structure of the two sides of the valve exhibited photon trapping and forward scattering of blue light enhancing photosynthetic active radiation inside the cell. Photonic structures of diatom frustules thus alter the cellular light field with implications on diatom photobiology.

We observe reversible light assisted formation and evaporation of rubidium clusters embedded in nanoporous silica. Metallic nanoparticles are cyclically produced and evaporated by weak blue-green and near-infrared light, respectively. The atoms photodetached from the huge surface of the silica matrix build up clusters, whereas cluster evaporation is increased by induced surface plasmon excitation. Frequency tuning of light activates either one process or the other and the related changes of glass transparency become visible to the naked eye. We demonstrate that the porous silica, loaded with rubidium, shows memory of illumination sequences behaving as a rereadable and rewritable optical medium. These processes take place as a consequence of the strong confinement of atoms and particles at the nanoscale.

Diatoms are ubiquitous organisms in aquatic environments and are estimated to be responsible for 20-25 % of the total global primary production. A unique feature of diatoms is the silica wall, called the frustule. The frustule is characterized by species-specific intricate nanopatterning in the same size range as wavelengths of visible and ultraviolet (UV) light. This has prompted research into the possible role of the frustule in mediating light for the diatoms' photosynthesis as well as into possible photonic applications of the diatom frustule. One of the possible biological roles, as well as area of potential application, is UV protection. In this review, we explore the possible adaptive value of the silica frustule with focus on research on the effect of UV radiation on diatoms. We also explore the possible effect of the frustules on UV radiation, from a theoretical, biological, and applied perspective, including recent experimental data on UV transmission of diatom frustules.