Ablation of calcified biological tissue using pulsed hydrogen fluoride laser radiation

Izatt, Joseph A.; Sankey, N. D.; Partovi, F.; Fitzmaurice, Maryann; Rava, Richard P.; Itzkan, J.; Feld, Michael S.

doi:10.1109/3.64362

Cited by 64 publications

(43 citation statements)

References 11 publications

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“…Laser fluence, optical resolution, and production speed have been refined to such high levels that today it is the actual laser ablation-generated debris that is stymieing progress [4]. Debris can contribute to beam attenuation after ejection but before deposition [5] and can be generated in a mode that coats unimportant areas, areas still to be machined, or, worse still, features that have already been machined [6]. To compound matters, debris can coat machinery, requiring costly downtime for cleaning and servicing [7], or can become airborne in the working environment of tool users, posing potential respiratory health issues [7].…”

Section: Background and Rationalmentioning

confidence: 99%

Excimer Laser Machining of Bisphenol a Polycarbonate under Closed Immersion Filtered Water with Varying Flow Velocities and the Effects on the Etch Rate

Dowding

Lawrence

2010

Proceedings of the Institution of Mechanical Engineers, Part B:

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• This is an article from the journal, Proceedings of the IMechE, Part B: Abstract: Until now, progress in laser ablation micromachining has been significantly limited with respect to feature miniaturization and output yield by ablation-generated debris. Gasjetting techniques have proven to be inadequate and vacuum environments are unwieldy in an industrial setting. To this end, a controlled geometry for both the optical interfaces of a flowing liquid film can be provided by a closed flowing thick film filtered water immersion technique. This ensures repeatable machining conditions and allows control of liquid flow velocity. To investigate the impact of this technique on etch rate, bisphenol A polycarbonate samples have been machined using KrF excimer laser radiation passing through a medium of filtered water flowing at a number of flow velocities that are controllable by modifying liquid flowrate. A mean increase in etch rate of 8.5 per cent when using a turbulent flow velocity regime immersed ablation over ablation in ambient air was recorded. However, use of laminar flow velocities resulted in a mean loss of 26.6 per cent in etch rate compared to ablation in ambient air. Plotting the recorded etch rate achieved with respect to flow velocity gives support for previously proposed flow-plume interactions: the primary cause of a 37 per cent variance in etch rate over a 72 per cent change in laminar flow velocity was a shift in the ratio between the refresh rate of liquid volume over the feature and laser repetition rate. The small variance of etch rate achieved by modification of turbulent regime flow velocity indicates that laser etching provided the dominating contribution to the total etch rate measured. This work demonstrates that this technique developed for ablation debris control does not reduce the efficiency of laser etching with respect to that achieved with established gas media laser ablation machining. Therefore, this process shows great promise for industrial implementation development.

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Section: Background and Rationalmentioning

confidence: 99%

Excimer Laser Machining of Bisphenol a Polycarbonate under Closed Immersion Filtered Water with Varying Flow Velocities and the Effects on the Etch Rate

Dowding

Lawrence

2010

Proceedings of the Institution of Mechanical Engineers, Part B:

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“…However, one area has continued to plague the laser ablation pattern machining sector: laser ablation generated debris [4]. Debris provides a number of technical obstacles: during machining [5]; after machining [6]; to the production tooling and facility [7] and potentially to the health of the facility workers [8]. These above issues make an efficient and general solution a desirable prospect.…”

Section: Introductionmentioning

confidence: 99%

Ablation debris control by means of closed thick film filtered water immersion

Dowding

Lawrence

2009

Proceedings of the Institution of Mechanical Engineers, Part B:

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Abstract:The performance of laser ablation generated debris control by means of open immersion techniques have been shown to be limited by flow surface ripple effects on the beam and the action of ablation plume pressure loss by splashing of the immersion fluid. To eradicate these issues a closed technique has been developed which ensured a controlled geometry for both the optical interfaces of the flowing liquid film. This had the action of preventing splashing, ensuring repeatable machining conditions and allowed for control of liquid flow velocity. To investigate the performance benefits of this closed immersion technique bisphenol A polycarbonate samples have been machined using filtered water at a number of flow velocities. The results demonstrate the efficacy of the closed immersion technique: a 93% decrease in debris is produced when machining under closed filtered water immersion; the average debris particle size becomes larger, with an equal proportion of small and medium sized debris being produced when laser machining under closed flowing filtered water immersion; large debris is shown to be displaced further by a given flow velocity than smaller debris, showing that the action of flow turbulence in the duct has more impact on smaller debris. Low flow velocities were found to be less effective at controlling the positional trend of deposition of laser ablation generated debris than high flow velocities; but, use of excessive flow velocities resulted in turbulence motivated deposition. This work is of interest to the laser micromachining community and may aide in the manufacture of 2.5D laser etched patterns covering large area wafers and could be applied to a range of wavelengths and laser types.

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“…The work on ablation threshold of teeth using a (Hydrogen Fluoride?) HF pulsed laser reported a threshold of 10-15 mJ/mm 2 (1-1.5 J/cm 2 ), the explosive evaporation level of water causing mass ejection from teeth 2) . The higher value of the ablation threshold of 150-200 mJ/mm 2 (15-20 J/cm 2 ) for direct evaporation of the hard components of the teeth itself accompanied by plasma formation has been reported.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of FEL Irradiation onto Human Enamel and Dentin

Tanaka

Sato

Tanimoto

et al. 2005

J. Hard Tissue Biology.

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Wavelength tunable Free Electron Laser, FEL, was irradiated onto the polished surfaces of human tooth enamel and dentin using the FEL system at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. LEBRA-FEL system was so powerful that only 2 mJ/pulse shot resulted in an apparent pit on the surfaces. The pit showed neither marked scorch nor formation of secondary crystalline phase revealed by micro-XRD and micro-FTIR. Optimum wavelength for pit formation on the dental hard tissues was about 3.0 mm. However, the optimum wavelengths for enamel and dentin should be at 3.2 mm, 3.0 mm, respectively. The results strongly suggested that the ablation mechanism by laser irradiation for dental hard tissues might be not the simple interaction of laser beams with water, but complex phenomena, which could not be neglected of the hard tissue components and structure.

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Ablation of calcified biological tissue using pulsed hydrogen fluoride laser radiation

Cited by 64 publications

References 11 publications

Excimer Laser Machining of Bisphenol a Polycarbonate under Closed Immersion Filtered Water with Varying Flow Velocities and the Effects on the Etch Rate

Excimer Laser Machining of Bisphenol a Polycarbonate under Closed Immersion Filtered Water with Varying Flow Velocities and the Effects on the Etch Rate

Ablation debris control by means of closed thick film filtered water immersion

Experimental Study of FEL Irradiation onto Human Enamel and Dentin

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