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Lasers in Surgery and Medicine Oct 2021In this study, the threshold fluences for disrupting the melanosomes for pigmented skin lesion treatment were determined using a 755-nm picosecond laser for clinical...
BACKGROUND AND OBJECTIVES
In this study, the threshold fluences for disrupting the melanosomes for pigmented skin lesion treatment were determined using a 755-nm picosecond laser for clinical use. Based on the melanosome disruption thresholds, incident fluences corresponding to the target lesion depths were evaluated in silico for different laser spot sizes.
STUDY DESIGN/MATERIALS AND METHODS
Melanosome samples were isolated from porcine eyes as alternative samples for human cutaneous melanosomes. The isolated melanosomes were exposed to 755-nm picosecond laser pulses to measure the mean particle sizes by dynamic light scattering and confirm their disruption by scanning electron microscopy. The threshold fluences were statistically determined from the relationships between the irradiated fluences and the mean particle sizes. Incident fluences of picosecond laser pulses for the disruption of melanosomes located at different depths in skin tissue were calculated through a light transport simulation using the obtained thresholds.
RESULTS
The threshold fluences of 550- and 750-picosecond laser pulses were determined to be 2.19 and 2.49 J/cm , respectively. The numerical simulation indicated that appropriate incident fluences of picosecond laser pulses differ depending on the depth distribution of the melanosomes in the skin tissue, and large spot sizes are desirable for disrupting the melanosomes more deeply located within the skin tissue.
CONCLUSION
The threshold fluences of picosecond laser pulses for melanosome disruption were determined. The incident fluence analysis based on the thresholds for melanosome disruption provides valuable information for the selection of irradiation endpoints for picosecond laser treatment of pigmented skin lesions. Lasers Surg. Med. © 2021 The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals LLC.
Topics: Animals; Humans; Lasers; Melanosomes; Pigmentation Disorders; Skin; Swine
PubMed: 33604920
DOI: 10.1002/lsm.23391 -
Lasers in Surgery and Medicine Jan 2021Laser-pumped lasers enable driving a secondary wavelength through pumping with a primary device. Here we investigate the first 730 nm laser-pumped laser for efficacy...
BACKGROUND AND OBJECTIVES
Laser-pumped lasers enable driving a secondary wavelength through pumping with a primary device. Here we investigate the first 730 nm laser-pumped laser for efficacy in tattoo removal.
STUDY DESIGN/MATERIALS AND METHODS
Fifteen subjects with 20 tattoos were enrolled to investigate the effect of a new 730 nm, titanium-sapphire laser-pumped laser at removing decorative tattoos. A total of four treatments were administered and photographic improvement of pre- and post-treatment cross-polarized digital images was evaluated by four blinded physician observers using an 11-point scale.
RESULTS
Blinded assessment of pre- and post-treatment images found 70%, 77%, 83%, 83%, 26%, and 8% clearance from baseline images for black, green, blue, purple, red and yellow pigments, respectively. Side effects were limited to pinpoint bleeding and erythema immediately after treatment and some crusting and scale up to 1-2 weeks following treatment, and a localized allergic reaction in a single subject. There was no scarring or pigmentary alteration visible in any follow-up images.
CONCLUSION
The new 730 nm, picosecond-domain, titanium-sapphire, laser-pumped laser is safe and effective for removing multicolored tattoos. Green, blue, and purple pigments cleared the most as expected, but black ink cleared more completely than was predicted. Lasers Surg. Med. © 2020 The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals LLC.
Topics: Humans; Laser Therapy; Lasers; Photography; Pigmentation Disorders; Tattooing
PubMed: 32212171
DOI: 10.1002/lsm.23237 -
Materials (Basel, Switzerland) Jun 2022Laser surface texture is very effective in antifriction systems, but its applications and research in dry friction are not enough. In this study, the groove texture was...
Laser surface texture is very effective in antifriction systems, but its applications and research in dry friction are not enough. In this study, the groove texture was prepared on the surface of 0Cr17Ni7Al stainless steel, a common material of sliding bearing, by nanosecond and femtosecond laser, respectively. The tribological properties of the two kinds of laser groove textures with different collision frequencies were studied in depth. The results show that the friction coefficients of groove texture prepared by nanosecond and picosecond lasers are lower than that of the untextured surface. The antifriction characteristics of the laser texture are very good. The average friction coefficient of nanosecond texture at the rotation radius of 15 mm is Z = 0.7318. The best friction-reducing effect is achieved. In general, the friction coefficient of nanosecond texture is lower than that of picosecond texture. When the friction radius is 22.5 mm and the number of collisions is 24,000, the lowest picosecond texture wear rate is = 3.342 × 10 mm/N·mm. However, when the radius is 15 mm and the collision frequency is 36,000 times, the wear rate of nanosecond texture reaches the highest = 13.680 × 10 mm/N·mm. The wear rate of the untextured surface has been exceeded. It can be seen that not all rotation radius textures are more wear-resistant than untextured surfaces. In addition, nanosecond groove texture and picosecond groove texture seem to produce different tribological properties. It is found that, under the same friction experimental conditions, different collision frequencies will affect the friction and wear properties of nanosecond and picosecond groove-textured surfaces.
PubMed: 35806542
DOI: 10.3390/ma15134419 -
Pharmaceutics Feb 2022Picosecond or nanosecond-domain non-ablative lasers generate faster photothermal effects and cause less injury than microsecond lasers. In this study, we investigated...
Cutaneous Delivery of Cosmeceutical Peptides Enhanced by Picosecond- and Nanosecond-Domain Nd:YAG Lasers with Quick Recovery of the Skin Barrier Function: Comparison with Microsecond-Domain Ablative Lasers.
Picosecond or nanosecond-domain non-ablative lasers generate faster photothermal effects and cause less injury than microsecond lasers. In this study, we investigated the enhancing effect of 1064 nm picosecond- and nanosecond-domain neodymium (Nd):yttrium-aluminum-garnet (YAG) lasers on the cutaneous delivery of cosmeceutical peptides. Microsecond-domain fractional ablative CO and fully ablative erbium (Er):YAG lasers were also used for comparison. In the Franz diffusion cell study, pig or mouse skin was treated with a laser before exposure to palmitoyl tripeptide (PT)-1, PT-38, and copper tripeptide (CT)-1 at a concentration of 150 μM. Psoriasiform, atopic dermatitis (AD)-like, and photoaged skins were also developed as permeation barriers. The non-ablative laser elicited the ultrastructural disruption of the stratum corneum and epidermal vacuolation. All laser modalities significantly increased the skin permeation of peptides in vitro. The non-ablative laser chiefly enhanced peptide delivery to the receptor compartment, whereas the ablative laser mainly increased the intracutaneous peptide deposition. The picosecond- and nanosecond-domain Nd:YAG lasers elevated the amount of PT-1 in the receptor up to 40- and 22-fold compared with untreated skin, respectively. Laser treatment promoted peptide delivery in barrier-deficient and inflamed skins, although this enhancement effect was less than that observed in healthy skin. Fluorescence microscopy indicated the capability of the non-ablative laser to deliver peptides to deeper skin strata. The ablative laser confined the peptide distribution in the epidermis. Confocal microscopy showed that peptides penetrated the skin along the microdots created by the fractional Nd:YAG and CO lasers. The skin barrier function determined by transepidermal water loss suggested quick recovery when using a nanosecond-domain laser (within 4 h). A longer period was needed for the skin treated with the fully ablative Er:YAG laser (76-84 h). Nanosecond non-ablative laser-facilitated peptide delivery may become an efficient and safe approach for cosmeceutical applications.
PubMed: 35214181
DOI: 10.3390/pharmaceutics14020450 -
Journal of Applied Crystallography Feb 2021A recent article by Von Dreele, Clarke & Walsh [ (2021), , https://doi.org/10.1107/S1600576720014624] introduces an entirely new paradigm in structure determination,...
A recent article by Von Dreele, Clarke & Walsh [ (2021), , https://doi.org/10.1107/S1600576720014624] introduces an entirely new paradigm in structure determination, where a complete structural measurement is made in a tenth of a nanosecond.
PubMed: 33833636
DOI: 10.1107/S1600576721000704 -
Advanced Science (Weinheim,... May 2023Epitaxial heterostructures of colloidal lead halide perovskite nanocrystals (NCs) with other semiconductors, especially the technologically important metal...
Epitaxial heterostructures of colloidal lead halide perovskite nanocrystals (NCs) with other semiconductors, especially the technologically important metal chalcogenides, can offer an unprecedented level of control in wavefunction design and exciton/charge carrier engineering. These NC heterostructures are ideal material platforms for efficient optoelectronics and other applications. Existing methods, however, can only yield heterostructures with random connections and distributions of the two components. The lack of epitaxial relation and uniform geometry hinders the structure-function correlation and impedes the electronic coupling at the heterointerface. This work reports the synthesis of uniform, epitaxially grown CsPbBr /CdS Janus NC heterostructures with ultrafast charge separation across the electronically coupled interface. Each Janus NC contains a CdS domain that grows exclusively on a single {220} facet of CsPbBr NCs. Varying reaction parameters allows for precise control in the sizes of each domain and readily modulates the optical properties of Janus NCs. Transient absorption measurements and modeling results reveal a type II band alignment, where photoexcited electrons rapidly transfer (within ≈9 picoseconds) from CsPbBr to CdS. The promoted charge separation and extraction in epitaxial Janus NCs leads to photoconductors with drastically improved (approximately three orders of magnitude) responsivity and detectivity, which is promising for ultrasensitive photodetection.
PubMed: 36840658
DOI: 10.1002/advs.202206560 -
Nanomaterials (Basel, Switzerland) Aug 2019Metal nanostructures are, nowadays, extensively used in applications such as catalysis, electronics, sensing, optoelectronics and others. These applications require the... (Review)
Review
Metal nanostructures are, nowadays, extensively used in applications such as catalysis, electronics, sensing, optoelectronics and others. These applications require the possibility to design and fabricate metal nanostructures directly on functional substrates, with specifically controlled shapes, sizes, structures and reduced costs. A promising route towards the controlled fabrication of surface-supported metal nanostructures is the processing of substrate-deposited thin metal films by fast and ultrafast pulsed lasers. In fact, the processes occurring for laser-irradiated metal films (melting, ablation, deformation) can be exploited and controlled on the nanoscale to produce metal nanostructures with the desired shape, size, and surface order. The present paper aims to overview the results concerning the use of fast and ultrafast laser-based fabrication methodologies to obtain metal nanostructures on surfaces from the processing of deposited metal films. The paper aims to focus on the correlation between the process parameter, physical parameters and the morphological/structural properties of the obtained nanostructures. We begin with a review of the basic concepts on the laser-metal films interaction to clarify the main laser, metal film, and substrate parameters governing the metal film evolution under the laser irradiation. The review then aims to provide a comprehensive schematization of some notable classes of metal nanostructures which can be fabricated and establishes general frameworks connecting the processes parameters to the characteristics of the nanostructures. To simplify the discussion, the laser types under considerations are classified into three classes on the basis of the range of the pulse duration: nanosecond-, picosecond-, femtosecond-pulsed lasers. These lasers induce different structuring mechanisms for an irradiated metal film. By discussing these mechanisms, the basic formation processes of micro- and nano-structures is illustrated and justified. A short discussion on the notable applications for the produced metal nanostructures is carried out so as to outline the strengths of the laser-based fabrication processes. Finally, the review shows the innovative contributions that can be proposed in this research field by illustrating the challenges and perspectives.
PubMed: 31390842
DOI: 10.3390/nano9081133 -
Lasers in Surgery and Medicine May 2018Green, blue, and purple tattoo pigments are often the colors most resistant to laser removal. Recently, the first ever production picosecond-domain laser with a 785 nm...
BACKGROUND
Green, blue, and purple tattoo pigments are often the colors most resistant to laser removal. Recently, the first ever production picosecond-domain laser with a 785 nm wavelength was developed to improve the rate of clearance of green, blue, and purple tattoo inks.
METHODS
Twenty-two tattoos from 15 subjects with skin phototypes II-IV were enrolled in the study. A total of four treatments were administered using a single 785 nm picosecond-domain laser wavelength. Blinded assessment of digital, cross-polarized photographs taken approximately 8 weeks following the last treatment was performed using an 11-point clearance scale.
RESULTS
Fourteen subjects with 21 tattoos completed all study visits. The 21 tattoos contained the following pigments: black (n = 15), green (n = 13), blue (n = 8), yellow (n = 5), purple (n = 4), and red (n = 3). Treatments were performed with a 2-4-mm beam diameter and fluences ranging from 1.1 to 3.1 J/cm . Blinded assessment of photographs found 85%, 81%, 74%, 61%, 11%, and 5% clearance from baseline photos for purple, blue, green, black, red, and yellow pigments, respectively. Treatments were well tolerated with typical erythema, edema and one case of pinpoint bleeding. No scarring was noted.
CONCLUSION
This first study of a new 785 nm picosecond-domain laser demonstrates safe and effective removal of multicolor tattoos. Although clearance was shown for a multitude of colors including black, the 785 nm laser wavelength has special affinity to purple, blue and green tattoo pigments. Lasers Surg. Med. 9999:1-7, 2018. © 2018 The Authors. Lasers in Surgery and Medicine Published by Wiley Periodicals, Inc.
PubMed: 29781161
DOI: 10.1002/lsm.22942 -
Scientific Reports Mar 2019Optical pulses from picosecond lasers can be delivered to the skin as single, flat-top beams or fractionated beams using a beam splitter or microlens array (MLA). In...
Optical pulses from picosecond lasers can be delivered to the skin as single, flat-top beams or fractionated beams using a beam splitter or microlens array (MLA). In this study, picosecond neodymium:yttrium aluminum garnet laser treatment using a single flat-top beam and an MLA-type beam at the wavelengths of 532 nm and 1,064 nm were delivered on ex vivo genotype-regulated, pigmented micropig skin. Skin specimens were obtained immediately after treatment and microscopically analyzed. Single flat-top beam treatment at a wavelength of 532 nm and a fluence of 0.05-J/cm reduced melanin pigments in epidermal keratinocytes and melanocytes, compared to untreated controls. Additionally, 0.1 J/cm- and 1.3 J/cm-fluenced laser treatment at 532 nm elicited noticeable vacuolation of keratinocytes and melanocytes within all epidermal layers. Single flat-top beam picosecond laser treatment at a wavelength of 1,064 nm and a fluence of 0.18 J/cm also reduced melanin pigments in keratinocytes and melanocytes. Treatment at 1,064-nm and fluences of 1.4 J/cm and 2.8 J/cm generated increasing degrees of vacuolated keratinocytes and melanocytes. Meanwhile, 532- and 1,064-nm MLA-type, picosecond laser treatment elicited fractionated zones of laser-induced micro-vacuolization in the epidermis and dermis. Therein, the sizes and degrees of tissue reactions differed according to wavelength, fluence, and distance between the microlens and skin.
Topics: Animals; Lasers, Solid-State; Lenses; Pigmentation; Skin; Swine
PubMed: 30862808
DOI: 10.1038/s41598-019-41021-7 -
Photoacoustics Apr 2023Longitudinal acoustic modes in planar thin gold films are excited and detected by a combination of ultrafast pump-probe photoacoustic spectroscopy and a surface plasmon...
Longitudinal acoustic modes in planar thin gold films are excited and detected by a combination of ultrafast pump-probe photoacoustic spectroscopy and a surface plasmon resonance (SPR) technique. The resulting high sensitivity allows the detection of acoustic modes up to the 7th harmonic (258 GHz) with sub-pm amplitude sensing capabilities. This makes a comparison of damping times of individual modes possible. Further, the dynamics of the real and imaginary part of the dielectric function and the film's thickness variation are separated by using the dependence of the amplitudes of the acoustic modes on the detection angle and the surface plasmon resonance. We find that longitudinal acoustic modes in the gold films mainly affect the real part of the dielectric function and highlight the importance to consider thickness related effects in acousto-plasmonic sensing.
PubMed: 36936710
DOI: 10.1016/j.pacs.2023.100464