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Register a new userThree-dimensional laser printing of macro-scale glass objects at a micro-scale resolution
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Three-dimensional (3D) printing has allowed for production of geometrically complex 3D objects with extreme flexibility, which is currently undergoing rapid expansions in terms of materials, functionalities, as well as areas of application. When attempting to print 3D microstructures in glass, femtosecond laser induced chemical etching (FLICE) has proved itself a powerful approach. Here, we demonstrate fabrication of macro-scale 3D glass objects of large heights up to ~3.8 cm with a well-balanced (i.e., lateral vs longitudinal) spatial resolution of ~20 {mu}m. The remarkable accomplishment is achieved by revealing an unexplored regime in the interaction of ultrafast laser pulses with fused silica which results in aberration-free focusing of the laser pulses deeply inside fused silica.
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Humanitys interest in manufacturing silica-glass objects extends back over three thousand years. Silica glass is resistant to heating and exposure to many chemicals, and it is transparent in a wide wavelength range. Due to these qualities, silica glass is used for a variety of applications that shape our modern life, such as optical fibers in medicine and telecommunications. However, its chemical stability and brittleness impede the structuring of silica glass, especially on the small scale. Techniques for three-dimensional (3D) printing of silica glass, such as stereolithography and direct ink writing, have recently been demonstrated, but the achievable minimum feature size is several tens of micrometers. While submicrometric silica-glass structures have many interesting applications, for example in micro-optics, they are currently manufactured using lithography techniques, which severely limits the 3D shapes that can be realized. Here, we show 3D printing of optically transparent silica-glass structures with submicrometric features. We achieve this by cross-linking hydrogen silsesquioxane to silica glass using nonlinear absorption of laser light followed by the dissolution of the unexposed material. We print a functional microtoroid resonator with out-of-plane fiber couplers to demonstrate the new possibilities for designing and building silica-glass microdevices in 3D.
Microbial-Induced Calcium carbonate (CaCO3) Precipitation (MICP) has been extensively studied for soil improvement in geotechnical engineering. The properties of calcium carbonate crystals such as size and quantity affect the strength of MICP-treated soil. This study demonstrates how the data from micro-scale microfluidic experiments that examine the effects of injection intervals and concentration of cementation solution on the properties of calcium carbonate crystals can be used to optimise the MICP treatment of macro-scale sand soil column experiments for effective strength enhancement. The micro-scale experiments reveal that, due to Ostwald ripening, longer injection intervals allow smaller crystals to dissolve and reprecipitate into larger crystals regardless of the concentration of cementation solution. By applying this finding in the macro-scale experiments, a treatment duration of 6 days, where injection intervals were 12 h, 24 h, and 48 h for cementation solution concentration of 0.25 M, 0.5 M and 1.0 M, respectively, was long enough to precipitate crystals large enough for effective strength enhancement. This was indicated by the fact that significantly higher soil strength and larger crystals were produced when treatment duration increased from 3 days to 6 days, but not when it increased from 6 days to 12 days.
We present a novel technique by which highly-segmented electrostatic configurations can be solved. The Robin Hood method is a matrix-inversion algorithm optimized for solving high density boundary element method (BEM) problems. We illustrate the capabilities of this solver by studying two distinct geometry scales: (a) the electrostatic potential of a large volume beta-detector and (b) the field enhancement present at surface of electrode nano-structures. Geometries with elements numbering in the O(10^5) are easily modeled and solved without loss of accuracy. The technique has recently been expanded so as to include dielectrics and magnetic materials.
We study the XY spin glass by large-scale Monte Carlo simulations for sizes up to 24^3, down to temperatures below the transition temperature found in earlier work. The data for the larger sizes show more marginal behavior than that for the smaller sizes indicating that the lower critical dimension is close to, and possibly equal to three. We find that the spins and chiralities behave in a very similar manner. We also address the optimal ratio of over-relaxation to Metropolis sweeps in the simulation.
Magnetic reconnection is a fundamental plasma process associated with conversion of the embedded magnetic field energy into kinetic and thermal plasma energy, via bulk acceleration and Ohmic dissipation. In many high-energy astrophysical events, magnetic reconnection is invoked to explain the non-thermal signatures. However, the processes by which field energy is transferred to the plasma to power the observed emission are still not properly understood. Here, via 3D particle-in-cell simulations of a readily available (TW-mJ-class) laser interacting with a micro-scale plasma slab, we show that when the electron beams excited on both sides of the slab approach the end of the plasma structure, ultrafast relativistic magnetic reconnection occurs in a magnetically-dominated (low-$beta$) plasma. The resulting efficient particle acceleration leads to the emission of relativistic electron jets with cut-off energy $sim$ 12 MeV. The proposed scenario can significantly improve understanding of fundamental questions such as reconnection rate, field dissipation and particle acceleration in relativistic magnetic reconnection.
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