Laser-absorbing Dye Research Articles

Selective laser sintering (SLS) of 3D printlets using a 3D printer comprised of IR/red-diode laser

The aim of this study was to employ and understand the feasibility of an infrared (IR)/red-diode laser with a wavelength of 808 nm for the selective laser sintering (SLS)-mediated sintering of 3D printlets, altering the dye composition and temperature variations. Kollicoat® IR (KIR) and an infrared (IR) laser-absorbing dye were physically mixed at various concentrations and subjected to SLS-mediated sintering to achieve 3D printlets by varying printing temperature (feed and print beds) at a fixed laser power ratio. Initially, the desired concentration of dye (1.25% w/w) was selected based on its sintering performance, and the same concentration was used to sinter the physical mixtures (PMs) at different feed bed temperatures (between 100 °C and 130 °C) and print bed temperature (120 °C to 150 °C), keeping the laser power ratio constant (1.0). It was found that good sintering performance was associated with a feed bed temperature of 130 °C and a print bed temperature of 150 °C. Printlets obtained from the aforementioned conditions showed highest dimensional accuracy (9.31 ± 0.30 mm diameter and 3.56 ± 0.04 mm thickness) in respect to feeded CAD dimensions (10 mm diameter and 3.60 mm thickness) with an average weight of 77.45 ± 4.56 mg. In addition, no physical/thermal or chemical degradation of the sintered 3D printlets was observed during the thermal and functional group analysis, respectively. Depending on the conditions given, we can conclude that an IR/red diode laser with a wavelength of 808 nm and a laser power ratio of 1.0 is feasible for sintering 3D printlets.

Single pulse development of chromium-deposited imprint micro/nano patterns of photo-cured crosslinked resin using a femtosecond pulsed laser

Exposure to a single pulse generated from a femtosecond pulsed laser for a duration of 100 fs at a wavelength of 800 nm and a laser fluence of 0.31 J cm−2 resulted in chromium (Cr) deposition on photocured insoluble imprint resin patterns to be ablated selectively; however, Cr deposition on synthetic quartz surfaces was retained. Single-pulse development of Cr-deposited imprint micro/nano patterns occurred at the same laser fluence, independent of the presence of a laser absorbing dye. Laser ablation of the cured resin near the Cr deposition was confirmed by atomic force microscopy. Depth profile analyses confirmed that Cr species were partially embedded in the cured resin underneath the layer of Cr. These results suggest that the mechanism of laser ablation was due to the rapid thermal expansion of resin near the embedded Cr species and deposited Cr layer rather than the multi-photon absorption of the cured resin.

Laser welding of polymers using unsymmetrical squaraine dyes

ABSTRACTTransmission laser welding of plastic is typically achieved by incorporating a laser absorbing dye into one of the two pieces of plastic one wishes to weld together and mediating the welding process using a laser emitting light at a suitable wavelength. Desirable properties of laser absorbing dyes include: (1) the dye is colorless in the visible region but absorbs strongly in the region at the wavelength where the laser emits, (2) the dye has a good conversion of the energy from the laser to heat, (3) the dye is stable enough to be incorporated into the molten plastic, (4) the dye is soluble in the plastic of choice to give an even distribution in the plastic, and (5) the dye is nontoxic. Here, we explore an alternative approach to achieve laser welding of colorless plastics using a laser dye that is colored, but that can be bleached after the welding process. Nonsymmetrical squaraine dyes were prepared by condensation of squaric acid and two equivalents of various 3,5‐dimethoxy‐N,N‐dialkylanilines. After the incorporation into polyethylene and laser welding, the plastic was bleached either by heat treatment or by irradiation with a high pressure Xe‐lamp giving colorless polyethylene. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 2245–2254

Laser Ignition of an Optically Sensitised Secondary Explosive by a Diode Laser

As a green technology, laser ignition of a relatively insensitive secondary explosive has been experimentally investigated. The explosive, hexanitrostilbene (HNS), was doped with one of two optical sensitizers, carbon black or a laser absorbing dye, and a continuous-wave (CW) infrared diode laser was used as the igniting source. The ignition sensitivities of HNS with each of the two optical sensitizers were analysed and compared in terms of: optical power threshold for ignition, ignition delay and full burn delay at various laser powers. The results have shown that both the chemical dye and carbon black optically sensitize the explosive with similar efficiencies. In contrast to the carbon black, the dye provides wavelength specificity and selectivity in the laser ignition process and its solubility in some specific solvents improves the coating of the explosive material. It was therefore concluded that the laser absorbing dye is a better candidate for optical sensitization in laser ignition than the commonly used carbon black. The combination of laser ignition sensitivity with wavelength selectivity potentially offers higher reliability and safety at a low optical power for future ignitors of secondary explosives.

Detection of anti-tumor immunity induced by laser immunotherapy.

Metastatic mammary tumors in rats were treated by laser immunotherapy. Tumors injected by a laserabsorbing dye and an immunoadjuvant were irradiated non-invasively by a near-infrared laser. The successfully cured rats developed a long-term resistance to repeated tumor challenges. Using the sera from cured rats as the source of primary antibodies, immune responses induced by laser immunotherapy were observed in both cellular and molecular levels using histochemical assays and Western blot analysis.

Selective photothermal interaction using an 805-nm diode laser and indocyanine green in gel phantom and chicken breast tissue.

Laser immunotherapy, a novel therapy for breast cancer, utilises selective photothermal interaction to raise the temperature of tumour tissue above the cell damage threshold. Photothermal interaction is achieved with intratumoral injection of a laser-absorbing dye followed by non-invasive laser irradiation. When tumour heating is used in combination with immunoadjuvant to stimulate an immune response, antitumour immunity can be achieved. In this study, the selective photothermal effect was investigated using gel phantom and chicken breast tissue. An 805-nm diode laser and indocyanine green (ICG) were used. An ICG-containing gelatin phantom was constructed to simulate targeted tumour tissue. The target gel was buried inside chicken breast tissue and the tissue-gel construct was irradiated by the laser. Temperatures at different locations in the construct were measured during the laser irradiation. For comparison, the thermal effect of an Nd:YAG laser on the tissue-gel construct was also investigated. Selective heating of target gel containing 0.27% ICG and buried 1 cm below the chicken tissue surface was achieved with the 805-nm diode laser using a power of 0.85 W and beam radius of 1 cm. The target gel experienced a temperature increase of more then 6 degrees C whereas the surrounding chicken breast tissue experienced only a minor temperature increase. The feasibility of this experimental set-up has been shown. It will be used in the future to optimise treatment parameters such as laser power, laser beam radius, and dye concentration.

Dynamically observing intratumor injection of laser-absorbing dye and immunoadjuvant using digital x-ray imaging technique

WeiR.ChenUniversity of Central OklahomaDepartment of Physics and EngineeringEdmond, Oklahoma 73034andUniversity of OklahomaDepartment of Physics and AstronomyNorman, Oklahoma 73109E-mail: wchen@ucok.eduHong LiuUniversity of OklahomaCenter for Bioengineering and School ofElectrical EngineeringNorman, Oklahoma 73019Wei YueJiping WangUniversity of VirginiaDepartment of Internal MedicineCharlottesville, Virginia 22908Robert E. NordquistUniversity of OklahomaDepartment of OphthalmologyOklahoma City, Oklahoma 73104andWound Healing of Oklahoma, Inc.3945 North Walnut StreetOklahoma City, Oklahoma 73105Abstract. Selective laser-tissue interaction is a promising method fornoninvasive treatment of deep tumors. Using a laser beam with a wave-length in the near-infrared region and an intratumoral injection of a laser-absorbing dye, the laser energy can destroy targeted tumor cells whilesparing normal surrounding tissue. Introducing an immunoadjuvant canachieve possible systemic antitumor immune response, hence augment-ing the selective laser-tissue interaction. Administration of the dye andthe immunoadjuvant, and the time window for optimal laser application,are crucial in determining the outcome of the treatment. To determinethe dynamic distribution of intratumor-injected laser-absorbing dye andimmunoadjuvant, a digital x-ray imaging technique was employed. In-docyanine green as the laser-absorbing dye and glycated chitosan asthe immunoadjuvant were injected into the center of a rat tumor, and thetransmitted x-ray signals through tumor tissue and surrounding normaltissue, before and after the injection, were acquired and analyzed. Thetransmitted signals through tissue were reduced due to the injection ofeither dye or immunoadjuvant solution. The diffusion of aqueous solu-tions in tissue was a function of time and of the properties of the solutes.The indocyanine green solution, due to its low molecular weight, diffusedthrough the tumor almost immediately after injection, then gradually dis-persed into the surrounding tissue. The glycated chitosan, on the otherhand, due to its high molecular weight and high viscosity, dispersedslowly and took about 20 to 25 min to reach maximum accumulation atthe edge of the tumor. Our results showed that the digital x-ray imagescould be used to guide the precise positioning of the injecting needle,and to determine the distributions of the dye and immunoadjuvant in thetumor and in the surrounding normal tissue. Apparently, the dynamicobservation of dye and immunoadjuvant administration and their diffu-sion process could be used to optimize the parameters for laser treat-ment of deep tumors.

Tumour Cell Damage and Leucocyte Infiltration after Laser Immunotherapy Treatment

Immune response after laser-photosensitiser application could be crucial in treatment of cancers, because without it there could be no systemic, long-term tumour control. Laser immunotherapy, a novel method for treatment of metastatic tumours, uses a near-infrared laser, a laser-absorbing dye indocyanine green, and an immunoadjuvant glycated chitosan. This modality has shown an induced antitumour immune response in treatment of rat mammary metastatic tumours. The influence of this new method on the cellular structure of the tumours and on the infiltrating immune cells was studied using optical and electron microscopes. The tumour samples were examined before and immediately after the treatment for acute effects, which appeared mainly photothermal. Two weeks after treatment, significant infiltrating lymphocytes and plasma cells were found around the surviving tumour cells. These morphological findings suggest that both cell-mediated and humoral immune responses could be responsible for the observed tumour eradication and induced long-term tumour resistance.

Controlled phase separation of polymer–liquid crystal mixtures for reversible optical data storage

A system for reversible optical data storage has been studied, using mixtures of polymers with liquid crystal molecules. A thin coating of a polymer-liquid crystal mixture with a laser absorbing dye would be spin coated onto a substrate and recording would be done with two types of write laser pulses. One laser pulse would be of high intensity and focused to small diameter, giving large temperature gradients and relatively fast cooling rates. The other write pulse would have lower intensity and larger diameter, resulting in smaller temperature gradients and slower cooling. A third pulse, reserved for reading, would not have sufficient intensity at the wavelength absorbed by the system to heat significantly. It would be scattered at different intensities into a photodetector depending on the cooling history of the spot being read. The feasibility of the principle was demonstrated through an experiment in which a 4-8-microm sample coating is applied to clear resistor coated glass. Energy was put into the system by a pulse generator whose power and pulse duration can be controlled. Low intensity laser light scattering patterns were observed during and after the resistive pulse to monitor the sample morphology during the experiment. A short heating pulse resulted in more intense light scattering at small angles than longer, lower power pulses.