Pressure generation during inertially confined laser ablation of biological tissue

Itzkan, Irving; Albagli, Douglas; Banish, Bryan; Dark, Marta; Rosenberg, Charles von; Perelman, Lev T.; Janes, G. S.; Feld, Michael S.

doi:10.1063/1.44847

Cited by 5 publications

(11 citation statements)

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“…There are, however, a significant number of experimental observations suggesting that ablation can be initiated at the energy densities much lower than those required for boiling and vaporization. Energetically efficient ablation has been reported for liquids, [26][27][28] polymers, 29 biological tissues, [30][31][32] and for organic matrixes used in infrared ͑IR͒-MALDI. 33 A plausible explanation for the onset of ''cold'' laser ablation has been proposed based on consideration of photomechanical effects caused by laser-induced stresses.…”

Section: Introductionmentioning

confidence: 99%

“…33 A plausible explanation for the onset of ''cold'' laser ablation has been proposed based on consideration of photomechanical effects caused by laser-induced stresses. 30,34,35 The magnitude of the laser-induced stresses and the role of the associated photomechanical effects in material removal depends on the relation between the rate of energy deposition and the characteristic time of mechanical equilibration of the absorbing volume, s . When the laser pulse duration is shorter or comparable to the time that is needed to initiate a collective motion of molecules within the absorbing volume, the laser heating takes place at nearly constant volume conditions, causing a high thermoelastic pressure buildup.…”

Section: Introductionmentioning

confidence: 99%

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Microscopic mechanisms of laser ablation of organic solids in the thermal and stress confinement irradiation regimes

Zhigilei

Garrison

2000

Journal of Applied Physics

406

480

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The results of large-scale molecular dynamics simulations demonstrate that the mechanisms responsible for material ejection as well as most of the parameters of the ejection process have a strong dependence on the rate of the laser energy deposition. For longer laser pulses, in the regime of thermal confinement, a phase explosion of the overheated material is responsible for the collective material ejection at laser fluences above the ablation threshold. This phase explosion leads to a homogeneous decomposition of the expanding plume into a mixture of liquid droplets and gas phase molecules. The decomposition proceeds through the formation of a transient structure of interconnected liquid clusters and individual molecules and leads to the fast cooling of the ejected plume. For shorter laser pulses, in the regime of stress confinement, a lower threshold fluence for the onset of ablation is observed and attributed to photomechanical effects driven by the relaxation of the laser-induced pressure. Larger and more numerous clusters with higher ejection velocities are produced in the regime of stress confinement as compared to the regime of thermal confinement. For monomer molecules, the ejection in the stress confinement regime results in broader velocity distributions in the direction normal to the irradiated surface, higher maximum velocities, and stronger forward peaking of the angular distributions. The acoustic waves propagating from the absorption region are much stronger in the regime of stress confinement and the wave profiles can be related to the ejection mechanisms.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Microscopic mechanisms of laser ablation of organic solids in the thermal and stress confinement irradiation regimes

Zhigilei

Garrison

2000

Journal of Applied Physics

406

480

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“…The role of photomechanical effects caused by the relaxation of the laser-induced stresses and the mechanisms of photomechanical damage and spallation revealed in the simulations and discussed above are in agreement with a number of analytical calculations and theoretical discussions of the role of photomechanical effects in laser ablation and damage. 33,115,118,[158][159][160][161] …”

Section: Photomechanical Effectsmentioning

confidence: 99%

Computer Simulations of Laser Ablation of Molecular Substrates

Zhigilei

Leveugle

Garrison³

et al. 2003

Chem. Rev.

281

248

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“…For ablation using short-pulsed lasers, there is evidence that photomechanical effects play the most significant role (1,3). Here it is presumed that, since most materials are weaker in tension than in compression, the material will fail wherever the induced tensile stresses exceed the tensile strength.…”

mentioning

confidence: 99%

“…Experimental evidence shows that both the amplitude of the stress and the time over which the stress operates are important. A general dynamic fracture criterion has been introduced by Tuler and Butcher, given a time-dependent tensile stress, o-ii(t) (11): [3] where A and K are constants and vi is a stress threshold below which fracture would not occur, even for long times. This formula states that fracture occurs when the cumulative product of stress above threshold to the A power and time reaches some critical value, K (A was empirically determined to be .1).…”

mentioning

confidence: 99%

The thermoelastic basis of short pulsed laser ablation of biological tissue.

Itzkan

Albagli

Dark

et al. 1995

Proc. Natl. Acad. Sci. U.S.A.

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Strong evidence that short-pulse laser ablation of biological tissues is a photomechanical process is presented. A full three-dimensional, time-dependent solution to the thermoelastic wave equation is compared to the results of experiments using an interferometric surface monitor to measure thermoelastic expansion. Agreement is excellent for calibrations performed on glass and on acrylic at low laser fluences. For cortical bone, the measurements agree well with the theoretical predictions once optical scattering is included. The theory predicts the presence of the tensile stresses necessary to rupture the tissue during photomechanical ablation. The technique is also used to monitor the ablation event both before and after material is ejected. TheoryExperimental results reported in the literature reveal that the energy density required to initiate ablation of biological tissue with nanosecond laser pulses is 10-fold less than that required for vaporization. This holds for a wide range of laser wavelengths (1, 2). When the laser pulse duration is shorter than a characteristic time, the material is "inertially confined"-i.e., it does not have time to expand, and heating takes place at constant volume.For ablation using short-pulsed lasers, there is evidence that photomechanical effects play the most significant role (1, 3). Here it is presumed that, since most materials are weaker in tension than in compression, the material will fail wherever the induced tensile stresses exceed the tensile strength. A onedimensional photomechanical model of laser-induced spallation correctly predicts the reduced energy density observed for nanosecond pulses. However, it also predicts that damage should first occur approximately one absorption depth beneath the surface (4, 5). In fact, ablation occurs at or near the surface. For the lasers and wavelengths used in ablating biological tissue, the optical absorption depth is usually comparable to the transverse laser dimension, and a onedimensional approximation is not appropriate. Onedimensional estimates made by our group did not correctly predict the observed surface movement, although they did account for the order of magnitude decrease in the energy required to reach threshold (1, 6). The various discrepancies can be reconciled by including three-dimensional effects. We have solved the full time-dependent three-dimensional equations, which predict that significant tensile stresses are created on the surface, precisely where ablation is observed to occur. All the time scales considered are much shorter than the time associated with thermal relaxation.When a material absorbs and is heated by laser energy, the resulting nonuniform temperature distribution causes internal forces, which lead to thermoelastic deformation. This deformation in a solid body is determined by the thermoelastic wave equation (7):3(l -2cr) [1] subject to the appropriate boundary and initial conditions, where u is the displacement vector, p is the density, E is Young's modulus, o is Poisson's ratio, X3...

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Pressure generation during inertially confined laser ablation of biological tissue

Cited by 5 publications

References 4 publications

Microscopic mechanisms of laser ablation of organic solids in the thermal and stress confinement irradiation regimes

Microscopic mechanisms of laser ablation of organic solids in the thermal and stress confinement irradiation regimes

Computer Simulations of Laser Ablation of Molecular Substrates

The thermoelastic basis of short pulsed laser ablation of biological tissue.

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