10 research outputs found
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Planar laser induced fluorescence for temperature measurement of optical thermocavitation
Pulsed laser-induced cavitation, has been the subject of many studies describing bubble growth, collapse and ensuing shock waves. To a lesser extent, hydrodynamics of continuous wave (CW) cavitation or thermocavitation have also been reported. However, the temperature field around these bubbles has not been measured, partly because a sensor placed in the fluid would interfere with the bubble dynamics, but also because the short-lived bubble lifetimes (∼70–200 µs) demand high sampling rates which are costly to achieve via infrared (IR) imaging. Planar laser-induced fluorescence (PLIF) provides a non-intrusive alternative technique to costly IR imaging to measure the temperature around laser-induced cavitation bubbles. A 440 nm laser sheet excites rhodamine-B dye to fluoresce while thermocavitation is induced by a CW 810 nm laser. Post-calibration, the fluorescence intensity captured with a high-speed Phantom Miro camera is correlated to temperature field adjacent to the bubble. Using shadowgraphy and PLIF, a significant decrease in sensible heat is observed in the nucleation site– temperature decreases after bubble collapse and the initial heated volume of liquid shrinks. Based on irradiation time and temperature, the provided optical energy is estimated to be converted up to 50% into acoustic energy based on the bubble's size, with larger bubbles converting larger percentages
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Ultrafast laser welding of ceramics.
Welding of ceramics is a key missing component in modern manufacturing. Current methods cannot join ceramics in proximity to temperature-sensitive materials like polymers and electronic components. We introduce an ultrafast pulsed laser welding approach that relies on focusing light on interfaces to ensure an optical interaction volume in ceramics to stimulate nonlinear absorption processes, causing localized melting rather than ablation. The key is the interplay between linear and nonlinear optical properties and laser energy-material coupling. The welded ceramic assemblies hold high vacuum and have shear strengths comparable to metal-to-ceramic diffusion bonds. Laser welding can make ceramics integral components in devices for harsh environments as well as in optoelectronic and/or electronic packages needing visible-radio frequency transparency
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Bubble dynamics of laser-induced cavitation in plasmonic gold nanorod solutions and the relative effect of surface tension and viscosity
Laser-induced cavitation (LIC) bubbles and the shockwaves they form upon collapse are destructive to nearby solid boundaries, making them of interest for biomedical and industrial applications. Furthermore, the LIC bubbles provide spatial control that can be tuned by the bubble size, collapse time and shockwave intensity. The inclusion of plasmonic nanoparticles, such as gold nanoparticles (GNP) in the liquids where LIC bubbles are formed, can further enhance the absorption of light, allowing for bubble formation at lower laser energies. However, the effect of the physical properties of such liquids on LIC bubble dynamics remains unknown. In this study, the dynamics of LIC bubbles in water–ethanol, water-glycerol, and water-GNP solutions were investigated by simultaneous high-speed shadowgraphy and spatial transmittance modulation. The first set of experiments demonstrated that LIC bubbles induced in the GNP solutions led to more efficient cavitation formation with lower fluence compared to solutions without GNPs, thereby producing higher-intensity pressure waves. A second set of experiments was conducted to determine the surface tension of GNP solutions at room temperature and was found to be 70.62 mN/m. With this information, and the corresponding values reported in the literature for ethanol and glycerol, we aimed at discerning the role of surface tension and viscosity on the dynamics of LIC bubbles, apart from the enhanced optical absorption of the GNP solutions. We observed that the optical breakdown threshold for plasma formation was reduced by 18% in GNP solutions as compared to DI water and 10.4% compared to ethanol, and the intensity of initial shockwaves in the GNP solutions was much higher than those in DI water. This enhanced intensity of shockwaves in GNP solutions compared to DI water opens a new avenue for the enhancement of cancer cell treatment and anti-bacterial applications in the biomedical field and the enhancement of the laser ablation technique in the industrial setting
Recommended from our members
Bubble dynamics of laser-induced cavitation in plasmonic gold nanorod solutions and the relative effect of surface tension and viscosity
Laser-induced cavitation (LIC) bubbles and the shockwaves they form upon collapse are destructive to nearby solid boundaries, making them of interest for biomedical and industrial applications. Furthermore, the LIC bubbles provide spatial control that can be tuned by the bubble size, collapse time and shockwave intensity. The inclusion of plasmonic nanoparticles, such as gold nanoparticles (GNP) in the liquids where LIC bubbles are formed, can further enhance the absorption of light, allowing for bubble formation at lower laser energies. However, the effect of the physical properties of such liquids on LIC bubble dynamics remains unknown. In this study, the dynamics of LIC bubbles in water–ethanol, water-glycerol, and water-GNP solutions were investigated by simultaneous high-speed shadowgraphy and spatial transmittance modulation. The first set of experiments demonstrated that LIC bubbles induced in the GNP solutions led to more efficient cavitation formation with lower fluence compared to solutions without GNPs, thereby producing higher-intensity pressure waves. A second set of experiments was conducted to determine the surface tension of GNP solutions at room temperature and was found to be 70.62 mN/m. With this information, and the corresponding values reported in the literature for ethanol and glycerol, we aimed at discerning the role of surface tension and viscosity on the dynamics of LIC bubbles, apart from the enhanced optical absorption of the GNP solutions. We observed that the optical breakdown threshold for plasma formation was reduced by 18% in GNP solutions as compared to DI water and 10.4% compared to ethanol, and the intensity of initial shockwaves in the GNP solutions was much higher than those in DI water. This enhanced intensity of shockwaves in GNP solutions compared to DI water opens a new avenue for the enhancement of cancer cell treatment and anti-bacterial applications in the biomedical field and the enhancement of the laser ablation technique in the industrial setting
Recommended from our members
Planar laser induced fluorescence for temperature measurement of optical thermocavitation
Pulsed laser-induced cavitation, has been the subject of many studies describing bubble growth, collapse and ensuing shock waves. To a lesser extent, hydrodynamics of continuous wave (CW) cavitation or thermocavitation have also been reported. However, the temperature field around these bubbles has not been measured, partly because a sensor placed in the fluid would interfere with the bubble dynamics, but also because the short-lived bubble lifetimes (∼70–200 µs) demand high sampling rates which are costly to achieve via infrared (IR) imaging. Planar laser-induced fluorescence (PLIF) provides a non-intrusive alternative technique to costly IR imaging to measure the temperature around laser-induced cavitation bubbles. A 440 nm laser sheet excites rhodamine-B dye to fluoresce while thermocavitation is induced by a CW 810 nm laser. Post-calibration, the fluorescence intensity captured with a high-speed Phantom Miro camera is correlated to temperature field adjacent to the bubble. Using shadowgraphy and PLIF, a significant decrease in sensible heat is observed in the nucleation site– temperature decreases after bubble collapse and the initial heated volume of liquid shrinks. Based on irradiation time and temperature, the provided optical energy is estimated to be converted up to 50% into acoustic energy based on the bubble's size, with larger bubbles converting larger percentages
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Soft material perforation via double-bubble laser-induced cavitation microjets
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High resolution optical experimental technique for computing pulsed laser-induced cavitation bubble dynamics in a single shot
The experiments conducted in this study consisted of a series of plasma generated cavitation bubbles in water, obtained by focusing a 532-nm Q-switched Nd:YAG nanosecond-pulsed laser. For the purpose of detection of such cavitation bubbles, a novel direct light transmission technique is used, referred to as spatial transmission modulation (STM), consisting of a nearly collimated beam of light passing through the sample at the point where the cavitation bubble is formed. The presence of the cavitation bubble modifies the direct light transmission, which is detected with a photodiode located at the opposite end. This is observed as an electrical signal response with an oscilloscope. A 1-megapixel high-speed video camera simultaneously records the cavitation event. The video was taken in an orthogonal direction with respect to the STM optical axis and was triggered simultaneously with an oscilloscope using the electronic synchronization signal from the pulsed laser. Data from the highspeed video was used to show that a computational spatial energetic analysis from the continuous laser probe beam is a valid method to directly obtain the cavitation bubble evolution from a single shot pulse. © 2013 by Begell House, Inc
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High resolution optical experimental technique for computing pulsed laser-induced cavitation bubble dynamics in a single shot
The experiments conducted in this study consisted of a series of plasma generated cavitation bubbles in water, obtained by focusing a 532-nm Q-switched Nd:YAG nanosecond-pulsed laser. For the purpose of detection of such cavitation bubbles, a novel direct light transmission technique is used, referred to as spatial transmission modulation (STM), consisting of a nearly collimated beam of light passing through the sample at the point where the cavitation bubble is formed. The presence of the cavitation bubble modifies the direct light transmission, which is detected with a photodiode located at the opposite end. This is observed as an electrical signal response with an oscilloscope. A 1-megapixel high-speed video camera simultaneously records the cavitation event. The video was taken in an orthogonal direction with respect to the STM optical axis and was triggered simultaneously with an oscilloscope using the electronic synchronization signal from the pulsed laser. Data from the highspeed video was used to show that a computational spatial energetic analysis from the continuous laser probe beam is a valid method to directly obtain the cavitation bubble evolution from a single shot pulse. © 2013 by Begell House, Inc
Recommended from our members
Ultrafast laser welding of ceramics.
Welding of ceramics is a key missing component in modern manufacturing. Current methods cannot join ceramics in proximity to temperature-sensitive materials like polymers and electronic components. We introduce an ultrafast pulsed laser welding approach that relies on focusing light on interfaces to ensure an optical interaction volume in ceramics to stimulate nonlinear absorption processes, causing localized melting rather than ablation. The key is the interplay between linear and nonlinear optical properties and laser energy-material coupling. The welded ceramic assemblies hold high vacuum and have shear strengths comparable to metal-to-ceramic diffusion bonds. Laser welding can make ceramics integral components in devices for harsh environments as well as in optoelectronic and/or electronic packages needing visible-radio frequency transparency