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The range of applications for additive manufacturing is expanding quickly, including mass production of athletic footwear parts.sup.1, dental ceramics.sup.2 and aerospace components.sup.3 as well as fabrication of microfluidics.sup.4, medical devices.sup.5, and artificial organs.sup.6. The light-induced additive manufacturing techniques.sup.7 used are particularly successful owing to their high spatial and temporal control, but such techniques still share the common motifs of pointwise or layered generation, as do stereolithography.sup.8, laser powder bed fusion.sup.9, and continuous liquid interface production.sup.10 and its successors.sup.11,12. Volumetric 3D printing.sup.13-20 is the next step onward from sequential additive manufacturing methods. Here we introduce xolography, a dual colour technique using photoswitchable photoinitiators to induce local polymerization inside a confined monomer volume upon linear excitation by intersecting light beams of different wavelengths. We demonstrate this concept with a volumetric printer designed to generate three-dimensional objects with complex structural features as well as mechanical and optical functions. Compared to state-of-the-art volumetric printing methods, our technique has a resolution about ten times higher than computed axial lithography without feedback optimization, and a volume generation rate four to five orders of magnitude higher than two-photon photopolymerization. We expect this technology to transform rapid volumetric production for objects at the nanoscopic to macroscopic length scales. By combining the use of photoswitchable photoinitators and intersecting light beams, objects and complex systems can be produced rapidly with higher definition than is possible using state-of-the art macroscopic volumetric methods., Author(s): Martin Regehly [sup.1] , Yves Garmshausen [sup.2] , Marcus Reuter [sup.2] , Niklas F. König [sup.2] , Eric Israel [sup.3] , Damien P. Kelly [sup.2] , Chun-Yu Chou [sup.2] [...]

Polarization-resolved second harmonic generation (P-SHG) microscopy is commonly used to analyze the second-order susceptibility, χ(2), tensor, which enables the calculation of the molecular structure of harmonophores. However, despite extensive research on type I collagen, the measured χ(2) ratios vary considerably among published values, which raises the question of whether P-SHG imaging is universally applicable to all tissues containing harmonophores. In this work, we propose that the deviation of χ(2) ratios is primarily due to ignoring the molecular tilt angle and chirality in image analysis. To confirm our hypothesis, we present an analytical model based on C6 symmetry that takes into account these two factors. We also introduce an imaging scheme that splits SHG into X- and Y-polarized image components for χ(2) tensor analysis. Our approach effectively improves the precision of determining χ(2) ratios, depending on how much the two factors affect the P-SHG signals. [ABSTRACT FROM AUTHOR]