Dual-color Technique Research Articles

Xolography for linear volumetric 3D printing.

The range of applications for additive manufacturing is expanding quickly, including mass production of athletic footwear parts1, dental ceramics2 and aerospace components3 as well as fabrication of microfluidics4, medical devices5, and artificial organs6. The light-induced additive manufacturing techniques7 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 stereolithography8, laser powder bed fusion9, and continuous liquid interface production10 and its successors11,12. Volumetric 3D printing13-20 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.

Standard thermography vs free emissivity dual color novel CIRA physics technique in the near-mid IR ranges: Studies for different emissivity class materials from low to high temperatures typical of aerospace re-entry

The dual color infrared thermography is a non-intrusive temperature measurement technique, based on the ratio principle between the signals collected at two near wavelengths in local grey body hypotheses and applicable when a thermal camera is equipped with a suitable pair of narrow band filters. In this work, the applicability at high temperatures has been investigated by using an analytical model based on Planck's Law integration, convoluted with the real response curves of sensors, optics, filters and attenuators. The presented model has been validated at high temperature and used to optimize the hardware set up for dual color measurements both in terms of operative spectral band and also for choosing the best pair of filters. Furthermore, spectral emissivity trend curves for different materials, available in literature, and at different temperatures have been used in the theoretical model in order to simulate and replicate experimental results. The experimental simulations obtained with dual color technique have been compared with those obtained through classical techniques based on the a priori knowledge and setting of the emissivity average values.The aim is to establish in which conditions and for which class of Thermal Protection System (TPS) materials used to protect the inner cold structure of hypersonic space vehicles made of aluminium or metallic alloys, the dual color technique can be used for a more accurate and precise temperature measurement compared to the classical techniques. The applicability study was carried out up to high temperature (2000 °C) which are reached by the TPS surfaces during the re-entry phase from Earth orbit or from interplanetary trajectories due to the high heat flux loads produced by the strong shock wave during the deceleration phase.

Free emissivity temperature investigations by dual color applied physics methodology in the mid- and long-infrared ranges

In this work a free emissivity (dual color) thermographic technique, based on the ratio of monochromatic emissive power, is investigated. It can be performed by equipping the InfraRed (IR) camera of two band pass filters in such a way to consider the emissivity parameter as a constant value. Two colour technique can reveal its utility in fields of applied physics where intrusive techniques are not allowed and/or materials are characterized by unknown emissivity. This physics methodology can be really useful, for example, in temperature determination of (Aero) Space materials (such as TPS-Thermal Protection Systems), tested on ground Plasma Wind Tunnel, solid targets temperature determination due to ions bombarding by means of accelerators for nuclear (Astro) Physics and/or environmental physics applications.In this paper, temperature measurement investigations based on the choice of central wavelength distances of two filters are reported. In particular a numerical model simulation, experimentally validated in the Long and Mid (LW, MW) – Wavelength ranges, was built and used to determine the feasibility of the technique and to choose the best filters combinations. In addition, after the verification capability in MW range, the temperature measurements on an aluminium plate were carried out with the dual colour technique. Moreover the verified numerical model was used to analyze errors of the two color technique in MW range using different curves of materials with variable emissivity. The study was carried out up to 500 °C and the results show that this innovative technique allows measurements of surface temperatures with errors of few % in MW range.

Error analysis on measurement temperature by means dual-color thermography technique

Dual color thermography is a non-contact measurement temperature technique used mainly when the emissivity of surface is unknown; it is based on ratio of monochromatic emissive power calculated by means Planck’s radiation equation and allows measuring the temperature of gray body surface objects without being assigned their emissivity and without approximations.For real surfaces, the emissivity varies with the temperature of surface as well as the wavelength and the direction of radiation. In this case, the dual color thermometry is executed by equipping the IR camera of two narrow band pass filters, so as to consider the surface emissivity of a quite constant value. This allows calculating the ratio between the radiative fluxes of the two different emission wavelengths that is almost independent to the surface emissivity.One of the crucial factor in this technique is the choice of the two narrow filter wavelengths. In fact the measurement errors depends directly on the two wavelengths and the variation of spectral emissivity related to the wavelength chosen and it also depends inversely on distance between central value of filters.In this paper, the authors have developed and validated a mathematical model of experimental setup to measure object surface temperature by means IR thermo-camera. This mathematical model was used to quantify the temperature measurement error in the dual-color technique. A novel correlation to estimate temperature measurement error was provided.

Characterization of Cytoplasmic / Membrane-Bound Protein Mixtures by Z-Scan Fluorescence Fluctuation Spectroscopy

Fluorescence fluctuation spectroscopy (FFS) has been employed to quantify the stoichiometry of soluble proteins in cells. However, some proteins have both soluble (cytoplasmic) and membrane-bound fractions. In such conditions, coexcitation of the membrane-bound and cytoplasmic proteins makes standard FFS unsuitable. In this work, we apply z-scan FFS to characterize the intensity profile of proteins with both a cytoplasmic and membrane-bound population. Analysis of the intensity profile determines unequivocally the intensity contributions from each membrane layer and the cytoplasm, as well as, the length of cytoplasm layer. Experimentally, we choose Matrix-EGFP (the MA domain of HTLV-1 Gag) as our model system and apply a dual color z-scan technique. Cells are cotransfected with Matrix-EGFP and mCherry and their emitted signal is split into two different detection channels based on color. Simultaneous fitting of both channels with separate model geometries aids in correct determination of parameters. The use of the dual color technique is possible because we demonstrate a co-localization of the observation volume and agreement in the point spread function shape factors for both the red and green channels. We extend our work by applying z-scan FFS to determine the brightness (stoichiometry) of the cytoplasmic protein fraction. Yet determining the brightness of the membrane-bound protein is significantly more challenging because of slower diffusion times, inhomogeneity in protein distribution, and possible brightness bias due to geometry and orientation effects. Here, we investigate the potential of z-scan FFS to address these factors and measure the unbiased brightness of membrane proteins. This study provides insight into the fundamental considerations for correct application of FFS in the study of proteins with both cytoplasmic and membrane-bound fractions. This work is supported by NIH grant GM064589 and NIH grant GM075401.