Fine Roughness Research Articles

Water-resistant properties improvement of aluminium oxide nanoparticles treated kraft paper by sparking process

This study aims to improve the hydrophobicity of non-sizing Kraft paper (KP) surfaces using nanoparticle coating through the sparking process. The aluminium oxide nanoparticles (Al2O3 NPs) were used for surface modification on KP through the sparking process, optimizing with varying sparking cycles (5–20 times), annealing temperatures (60–120 °C), and annealing times (1–3 h). Then, the Al2O3 NPs treated KP were examined by XRD, FT–IR, SEM, EDX, and AFM, respectively. The water contact angle (CA) was used to examine the water-resistant properties of the treated KP. The treated KP with varying sparking cycles up to 15 times showed higher surface coverage and enhanced fine roughness surface on the treated KP. The fine roughness surface of KP induced hydrophobicity (126° of CA) on the surface of KP at 15 sparking cycles. Similarly, the higher CA for hydrophobicity surface on treated KP from varying temperatures and times of the annealing process was demonstrated at 120° for 3 h. Therefore, the treated KP with 15 times of sparking cycle, annealing temperature at 120 °C for 3 h was defined as the optimized condition in this work. Furthermore, the developments of hydrophobicity and superhydrophobicity on the treated KP with CA at 135 and 155° were observed for the non-sizing and sizing KP, respectively. This indicated that the increased surface roughness and reduced surface energy of the treated KP simultaneously delayed the water absorption times on the KP surface. Consequently, the nano-treating of Al2O3 NPs using the sparking process shows the promising feature of inducing superhydrophobicity on the KP surface, which can produce a water-repellent corrugated box as an alternative packaging material.

On the adhesion of sinusoidal surfaces

In this work, we study the adhesive loading and unloading of a one-dimensional sinusoidal surface and use design of experiments to provide for response surface maps for the work of adhesion and the interaction length, which depend only on Johnson’s α parameter and the Maugis parameter μ. As showcased by some example, these can be used to replace the fine scale roughness by a cohesive zone model. Besides that, we provide ranges of α and μ in which the most common analytical solutions present accurate results. Finally, we characterize the presence of instabilities in the loading and unloading profiles.

Attachment Performance of Stick Insects (Phasmatodea) on Plant Leaves with Different Surface Characteristics.

Simple SummaryHerbivorous insects and plants greatly affected each other’s evolution due to their close interactions. This resulted in the development of a variety of adaptations on both sides. Through the need for protection against herbivorous insects, surfaces with lower attachment ability evolved in many plants. As a response, the attachment systems of insects have developed numerous specializations. Stick insects (Phasmatodea) have an attachment system, consisting of paired claws, arolium (attachment pad between the claws) and euplantulae (paired attachment pads on the tarsomeres), which is well adapted to different natural surfaces. We used measurements of pull-off and traction force in two species (Medauroidea extradentata and Sungaya inexpectata) representing the most common microstructures used for attachment within stick insects (nubby and smooth) to quantify the attachment ability of Phasmatodea on natural surfaces. Plant leaves with different surface properties (smooth, trichome-covered, hydrophilic and covered with crystalline waxes) were selected as substrates. Wax-crystal-covered fine-roughness substrates revealed the lowest, whereas strongly structured substrates showed the highest attachment performance among the stick insects studied. Removing the claws of the insects resulted in lower attachment ability on structured substrates. Furthermore, claw removal revealed that the attachment performance of the pads is less reduced by contaminating wax crystals in the species with nubby attachment structures. Long-lasting effects of the leaves on the attachment ability were briefly investigated, but not confirmed.Herbivorous insects and plants exemplify a longstanding antagonistic coevolution, resulting in the development of a variety of adaptations on both sides. Some plant surfaces evolved features that negatively influence the performance of the attachment systems of insects, which adapted accordingly as a response. Stick insects (Phasmatodea) have a well-adapted attachment system with paired claws, pretarsal arolium and tarsal euplantulae. We measured the attachment ability of Medauroidea extradentata with smooth surface on the euplantulae and Sungaya inexpectata with nubby microstructures of the euplantulae on different plant substrates, and their pull-off and traction forces were determined. These species represent the two most common euplantulae microstructures, which are also the main difference between their respective attachment systems. The measurements were performed on selected plant leaves with different properties (smooth, trichome-covered, hydrophilic and covered with crystalline waxes) representing different types among the high diversity of plant surfaces. Wax-crystal-covered substrates with fine roughness revealed the lowest, whereas strongly structured substrates showed the highest attachment ability of the Phasmatodea species studied. Removal of the claws caused lower attachment due to loss of mechanical interlocking. Interestingly, the two species showed significant differences without claws on wax-crystal-covered leaves, where the individuals with nubby euplantulae revealed stronger attachment. Long-lasting effects of the leaves on the attachment ability were briefly investigated, but not confirmed.

32663 Testing clinical efficacy of exfoliants against pollution and photoaging for healthy skin maintenance

Photoaging/environmental aging causes damage and wrecks human skin over the course of a life span. With pollutants, particulate matter, and photoaging, photodamage is superimposed on changes occurring with intrinsic aging. Clinical characteristics of cutaneous photoaging include fine lines, wrinkles, roughness, dullness, laxity, mottled pigmentation, and age spots/hyperpigmentation. The skin needs additional supportive care besides photoprotection with sunscreen and with antioxidants. Addition of plant exfoliants is becoming increasingly popular in keeping skin clean by breaking down the accumulation of particulate matter, removing dead cells/debris from the epidermis, exposing new cells, unclogging pores, and helping with age spots, brightening.

Holding on or falling off: The attachment mechanism of epiphytic Anthurium obtusum changes with substrate roughness.

For vascular epiphytes, secure attachment to their hosts is vital for survival. Yet studies detailing the adhesion mechanism of epiphytes to their substrate are scarce. Examination of the root hair-substrate interface is essential to understand the attachment mechanism of epiphytes to their substrate. This study also investigated how substrate microroughness relates to the root-substrate attachment strength and the underlying mechanism(s). Seeds of Anthurium obtusum were germinated, and seedlings were transferred onto substrates made of epoxy resin with different defined roughness. After 2 months of growth, roots that adhered to the resin tiles were subjected to anchorage tests, and root hair morphology at different roughness levels was analyzed using light and cryo scanning electron microscopy. The highest maximum peeling force was recorded on the smooth surface (glass replica, 0 µm). Maximum peeling force was significantly higher on fine roughness (0, 0.3, 12 µm) than on coarse (162 µm). Root hair morphology varied according to the roughness of the substrate. On smoother surfaces, root hairs were flattened to achieve large surface contact with the substrate. Attachment was mainly by adhesion with the presence of a glue-like substance. On coarser surfaces, root hairs were tubular and conformed to spaces between the asperities on the surface. Attachment was mainly via mechanical interlocking of root hairs and substrate. This study demonstrates for the first time that the attachment mechanism of epiphytes varies depending on substrate microtopography, which is important for understanding epiphyte attachment on natural substrates varying in roughness.

Thin Films Deposition of Ta2O5 and ZnO by E-Gun Technology on Co-Cr Alloy Manufactured by Direct Metal Laser Sintering.

In recent years in the dental field, new types of materials and techniques for the manufacturing of dental crowns and analog implants have been developed to improve the quality of these products. The objective of this article was to perform the surface characterization and determine the properties of Co-Cr alloy samples fabricated by the direct metal laser sintering (DMLS) process and coated by e-gun technology with thin films of Ta2O5 and ZnO. Both oxides are frequently used for dental products, in pharmacology, cosmetics, and medicine, due to their good anticorrosive, antibacterial, and photo-catalytic properties. Following the deposition of thin oxide films on the Co-Cr samples fabricated by DMLS, a very fine roughness in the order of nanometers was obtained. Thin films deposition was realized to improve the hardness and the roughness of the Co-Cr parts fabricated by the DMLS process. Surface characterization was performed using SEM-EDS, AFM, and XRD. AFM was used to determine the roughness of the samples and the nanoindentation curves were determined to establish the hardness values and modulus of elasticity.

Surface roughness variation and microstructural evolution of Au thin films in rapid annealing by microwave and electric furnace heating

Microstructural evolution of Au thin film in post-annealing by microwave and by electric furnace heating was compared. Wave number spectra of film surface roughness were analyzed to characterize their roughness variation by annealing. Coarsening of film microstructure occurred consistently as the increase of the annealing temperature in both methods. Labyrinth-shaped morphologies consisting of bump-ridge crystals were formed by annealing, which might be originated from the fine-grained colonies existed in the as-deposited state. Through coalescence and growth of the grains within the colony, the bump-ridge crystals increased their height as the increase of annealing temperature. Eventually, microstructures and crystal morphologies became similar by both annealing methods above 800–850 °C.However, there are following differences observed in the low temperature annealing cases: 1. While a temporal variation of the film microstructure was observed in furnace annealing, microwave annealing exhibited smaller tendency of this feature. 2. Fine roughness (higher wave number range) of the films was reduced more in the temperature below 720 °C by microwave annealing than by furnace annealing. 3. Increase of bump-ridge height was pronounced more by microwave annealing between 600 and 800 °C, corresponding to the roughness increase in the lower wave number range. On the other hand, film coverage decreased. The reasons for the difference was discussed by consideration of the competition among the capillary driven surface diffusion, contribution of electro-migration and the thermodynamic equilibrium shapes of the film grain structures.

Fabrication and characterization of cauliflower-like silica nanoparticles with hierarchical structure through ion beam irradiation

The fabrication of superhydrophobic surfaces is an area of great interest to assorted engineering applications for instance as self-cleaning, anti-biofouling, anti-corrosion, anti-icing, and anti-sticking materials. A simple and inexpensive fabrication process is required to manufacture superhydrophobic surfaces industrially. In this work, we developed a facile process for the fabrication of superhydrophobic surfaces with the use of ion-beam irradiation with argon and oxygen gases. The process of ion beam irradiation was applied to understand the effects of irradiation on the surface morphology and substrate properties. After ion-beam irradiation, the surface morphology was altered to include microstructures with various types of surface roughness and forms. The as-prepared structured surfaces exhibited a high static contact angle (greater than 150°) and excellent superhydrophobicity owing to the synergistic effects of low-surface-energy materials. These results indicate that improving the surface hydrophobicity may solve selected problems associated with surfaces. • A facile process was developed to fabricate superhydrophobic surfaces. • Surface morphology obtained with ion beam irradiation with argon and oxygen gas. • Fine nanoscale roughness was applied to larger microscale roughness. • A technologically viable method to create superhydrophobic surfaces is presented.

Sampling from rough energy landscapes

We examine challenges to sampling from Boltzmann distributions associated with multiscale energy landscapes. The multiscale features, or roughness, corresponds to highly oscillatory, but bounded, perturbations of a smooth landscape. Through a combination of numerical experiments and analysis we demonstrate that the performance of Metropolis Adjusted Langevin Algorithm can be severely attenuated as the roughness increases. In contrast, we prove that Random Walk Metropolis is insensitive to such roughness. We also formulate two alternative sampling strategies that incorporate large scale features of the energy landscape, while resisting the impact of fine scale roughness; these also outperform Random Walk Metropolis. Numerical experiments on these landscapes are presented that confirm our predictions. Open questions and numerical challenges are also highlighted.

Surface Roughness Variation and Microstrucural Evolution of AU Thin Films in Rapid Annealing by Microwave and Furnace Heating

Microstructural evolution of Au thin film in post-annealing by microwave and by electric furnace heating was compared. Wave number spectra of film surface roughness were analyzed to characterize their roughness variation by annealing. Coarsening of film microstructure occurred consistently as the increase of the annealing temperature in both methods. Labyrinth-shaped morphologies consisting of bump-ridge crystals were formed by annealing, which might be originated from the fine-grained colonies existed in the as-deposited state. Bumps were formed through coalescence and growth within the colony and increased their height as the increase of annealing temperature. Eventually, microstructures and crystal morphologies became similar by both annealing methods above 800~850°C. However, there are following differences observed in the low temperature annealing cases: 1. While a temporal variation of the film microstructure was observed in furnace annealing, microwave annealing exhibited smaller tendency of this feature. 2. Fine roughness (higher wave number range) of the films was reduced more in the temperature below 720oC by microwave annealing than by furnace annealing. 3. Bump height increase was pronounced more by microwave annealing between 600~800°C, corresponding to the roughness increase (RMS, root mean square value of the roughness). On the other hand, film coverage decreased. The reasons for the difference was discussed by consideration of the competition among the capillary driven surface diffusion, contribution of electro-migration and the thermodynamic equilibrium shapes of the film grain structures.

An advanced oil composition containing stabilized retinol with enhanced bioactivity improves the appearance of fine lines, wrinkles, skin roughness, mottled hyperpigmentation, and overall photodamage

An advanced oil composition containing stabilized retinol with enhanced bioactivity improves the appearance of fine lines, wrinkles, skin roughness, mottled hyperpigmentation, and overall photodamage

Effect of mixed hydrophilic and hydrophobic surface coatings on droplets freezing and subsequent frost growth during air forced convection channel flows

The formation of frost and ice decreases the energy efficiency of refrigeration systems and of air-source heat pump systems. This paper presents new experimental data of frost nucleation and frost growth on cold flat plates operating in frosting conditions with air forced convective flow. The plates surfaces had different wettability: from an uncoated aluminum surface with fine finish roughness and contact angle of 75°, to hydrophobic (θ ≈ 110–116°) and hydrophilic (θ ≈ 19–29°) coatings. Three biphilic coatings with regions of hydrophilic coatings adjacent to areas with hydrophobic coatings were investigated. These coatings manage water droplets movements, reduce freezing temperatures, and delay icing and onset of frost nucleation. A new experimental technique was developed in order to mimic actual field type operating conditions of convective channel flow experienced by fin structures of heat exchangers of typical air-source heat pump systems. Hydrophobic surface and one biphilic surface had early phase changeovers and high thresholds of the frost thickness before switching to the frost growth phase due to the presence of large droplets on the surfaces before they froze into ice beads. Fine-finished aluminum surface and hydrophilic coating had delayed phase changeovers and low frost thicknesses with respect to the other surfaces.

Modulating Fine Roughness Perception of Vibrotactile Textured Surface using Pseudo-haptic Effect.

Playing back vibrotactile signals through actuators is commonly used to simulate tactile feelings of virtual textured surfaces. However, there is often a small mismatch between the simulated tactile feelings and intended tactile feelings by tactile designers. Thus, a method of modulating the vibrotactile perception is required. We focus on fine roughness perception and we propose a method using a pseudo-haptic effect to modulate fine roughness perception of vibrotactile texture. Specifically, we visually modify the pointer's position on the screen slightly, which indicates the touch position on textured surfaces. We hypothesized that if users receive vibrational feedback watching the pointer visually oscillating back/forth and left/right, users would believe the vibrotactile surfaces more uneven. We also hypothesized that as the size of visual oscillation is getting larger, the amount of modification of roughness perception of vibrotactile surfaces would be larger. We conducted user studies to test the hypotheses. Results of first user study suggested that users felt vibrotactile texture with our method rougher than they did without our method at a high probability. Results of second user study suggested that users felt different roughness for vibrational texture in response to the size of visual oscillation. These results confirmed our hypotheses and they suggested that our method was effective. Also, the same effect could potentially be applied to the visual movement of virtual hands or fingertips when users are interacting with virtual surfaces using their hands.

Effect of Platelet-Rich Plasma Injection for Rejuvenation of Photoaged Facial Skin

There remains little experimental evidence and no randomized clinical trial to date to confirm the benefit of platelet-rich plasma (PRP) for facial rejuvenation. To investigate whether PRP injection improves the visual appearance, including texture and color, of photodamaged facial skin. In this randomized clinical trial, participants and raters were masked to groupings. The setting was an academic-based, urban outpatient dermatology practice in Chicago, Illinois. Participants were adults aged 18 to 70 years with bilateral cheek rhytids of Glogau class II or greater. The duration of the study was August 21, 2012, to February 16, 2016. Each participant received 3 mL intradermal injections of PRP to one cheek and sterile normal saline to the contralateral cheek. Primary outcomes were photoaging scores (with subscores for fine lines, mottled pigmentation, roughness, and sallowness) as rated by 2 masked dermatologists. Secondary outcomes included participant self-assessment scores of improvement on a 5-point scale (worsening, no change, mild improvement, moderate improvement, or significant improvement), participant overall satisfaction scores on a 4-point scale (not satisfied, slightly satisfied, moderately satisfied, or very satisfied), and participant-reported or investigator-observed adverse events. Of 27 enrolled participants, 19 (mean [SD] age, 46.37 [10.88] years; 17 female) were analyzed. Reported adverse events, which were not associated with the study agent, included redness (n = 18), swelling (n = 16), bruising (n = 14), pruritus (n = 1), skin scaling (n = 1), and dryness of skin (n = 1). No participants reported any adverse events at 12 months. Mean (SD) photoaging scores rated by 2 dermatologists showed no significant difference between PRP and normal saline for fine lines (baseline, 1.00 [0.75] vs 1.05 [0.78]; 2 weeks, 0.95 [0.71] vs 0.95 [0.71]; 3 months, 0.95 [0.71] vs 0.95 [0.71]; 6 months, 0.95 [0.71] vs 0.95 [0.71]), mottled pigmentation (baseline, 1.21 [0.53] vs 1.21 [0.54]; 2 weeks, 1.16 [0.60] vs 1.16 [0.60]; 3 months, 1.00 [0.47] vs 1.11 [0.46]; 6 months, 1.16 [0.69] vs 1.16 [0.69]), skin roughness (baseline, 0.47 [0.61] vs 0.47 [0.61]; 2 weeks, 0.47 [0.61] vs 0.47 [0.61]; 3 months, 0.47 [0.61] vs 0.47 [0.61]; 6 months, 0.37 [0.60] vs 0.37 [0.68]), and skin sallowness (baseline, 1.11 [0.88] vs 1.11 [0.88]; 2 weeks, 0.95 [0.85] vs 0.95 [0.85]; 3 months, 0.58 [0.61] vs 0.58 [0.61]; 6 months, 0.37 [0.68] vs 0.37 [0.68]). At 6 months after a single treatment, participants rated the PRP-treated side as significantly more improved compared with normal saline for texture (mean [SD] self-assessment score, 2.00 [1.20] vs 1.21 [0.54]; P = .02) and wrinkles (mean [SD] self-assessment score, 1.74 [0.99] vs 1.21 [0.54]; P = .03). Masked participants noted that both fine and coarse texture improved significantly more with a single treatment of PRP than with normal saline. Both participants and raters found PRP to be nominally but not significantly superior to normal saline. ClinicalTrials.gov Identifier: NCT01372566.

Effect of roughness on the adhesive tractions between contacting bodies

A method is proposed for estimating the effect of broad spectrum surface roughness on the adhesion between elastic bodies. At each length scale, the effect of fine scale roughness is modelled by a modified traction law whilst an added coarse scale increment is described by a probability distribution of mean gap as modified by elastic deformation. Instabilities occur for relatively smooth surfaces whose linear dimensions are sufficiently large to support long wavelength perturbations. The method is validated by comparison with direct numerical calculations, in the range where this is practicable. It is then applied to power-law spectra with various values of height variance and lower wavenumber cutoff. The results show that the effect of roughness is dominated by the height variance m0, but at lower wavenumber elastic deformation reduces the dependence on m0, except near the unstable range.

Development of breathable Janus superhydrophobic polyester fabrics using alkaline hydrolysis and blade coating

Alkaline hydrolysis is a common finishing method that is used to give polyester (polyethylene terephthalate, PET) a more natural touch and improved luster via chemical or physical changes in the fibers. However, its potential as a tool for surface modification in the development of single-sided superhydrophobic materials has not been studied yet. In this research, Janus superhydrophobic PET fabrics with asymmetric wetting properties (one side of the PET surface was rendered superhydrophobic while the other side was simply hydrophobic) were fabricated in two steps. Fine roughness was first achieved on the surface of PET fabrics by alkaline hydrolysis. Subsequently, optimized foam-coating emulsions were applied on only one surface of the alkaline-hydrolyzed PET. Alkaline treatment time, solution temperature, and viscosity of the foam-coating emulsions were varied to find optimal conditions in terms of structural changes, mechanical properties, superhydrophobicity, and absorption ability. The specimen treated with an aqueous solution of 8% sodium hydroxide at 70℃ for 60 min and coated with the mixture of the fluoro-emulsion and thickener in the volume ratio of 40:2 was determined to be the optimal conditions for the Janus superhydrophobic property. This sample showed a contact angle of 162.8° and a shedding angle of 5.6° on one side, whereas it completely permitted the percolation of water drops on the other side within 109 s. The mechanical properties of the developed Janus PET under the optimal conditions did not decrease significantly; its weight and tensile strength were found to have decreased by 3.3% and 19.2%, respectively. Furthermore, the single-sided superhydrophobic specimen demonstrated higher moisture transmissibility than the double-sided coated PET under the same alkaline treatment conditions. The method developed herein eliminates the requirement for an additional process to deliver nanoscale surface roughness and has the potential to produce waterproof–breathable PET fabrics for outdoor clothing.

A Maugis-Dugdale cohesive solution for adhesion of a surface with a dimple.

We study the adhesion of a surface with a 'dimple' which shows a mechanism for a bi-stable adhesive system in surfaces with spaced patterns of depressions, leading to adhesion enhancement, high dissipation and hysteresis. Recent studies were limited mainly to the very short range of adhesion (the so-called JKR regime), while we generalize the study to a Maugis cohesive model. A 'generalized Tabor parameter', given by the ratio of theoretical strength to elastic modulus, multiplied by the ratio of dimple width to depth has been found. It is shown that bistability disappears for generalized Tabor parameter less than about 2. Introduction of the theoretical strength is needed to have significant results when the system has gone in full contact, unless one postulates alternative limits to full contact, such as air entrapment, contaminants or fine scale roughness. Simple equations are obtained for the pull-off and for the full contact pressure in the entire set of the two governing dimensionless parameters. A qualitative comparison with results of recent experiments with nanopatterned bioinspired dry adhesives is attempted in light of the present model.

Optimizing surface characteristics for cell adhesion and proliferation on titanium plasma spray coatings on polyetheretherketone

BackgroundTitanium plasma spray coating on polyetheretherketone (PEEK) is a recent innovation to interbody spacer technology. The inherent hydrophobic properties of standard, uncoated PEEK implants can hamper cell attachment and bone healing during fusion. The addition of titanium coating not only offers initial stability due to increased surface roughness but also long-term stability due to bony ongrowth created from osteoconductive microenvironment on the device surface. The previously established hydrophilic and osteophilic properties of commercially pure titanium (CPTi) can potentially provide an ideal environment promoting cell attachment and bony ongrowth when applied at the end plate level of the fusion site. Because the surface material composition and topography is what seems to directly affect cell adhesion, it is important to determine the ideal titanium coating for the highest effectiveness. PurposeThe purpose of the study is to determine whether there is an optimal surface roughness for the titanium coatings and whether different polishing methods have a greater effect than roughness or topography in mediating cell adhesion to the surface. Study Design/SettingThe study was divided into two phases. In Phase 1, the effects of varying surface roughnesses on identical polishing method were compared. In Phase 2, the effect of varying polishing methods was compared on identical surface roughnesses. MethodsCoating thickness, porosity, and surface roughness were characterized using an optical microscope as per ASTM F 1854 standards. For both phases, PEEK coupons with plasma-sprayed CPTi were used, and human mesenchymal stem cells (hMSCs) at an initial density of 25,000 cells/cm2 were seeded and cultured for 24 hours before fixation in 10% formalin. The cultured hMSCs were visualized by 4′,6-diamidino-2-phenylindole (DAPI) staining, a fluorescent stain that binds to the DNA of living cells. Samples were imaged using an environmental scanning electron microscope (eSEM) (Carl Zeiss Microscopy, Thornwood, NY, USA) using a backscattered detector. ResultsImage analysis of the CPTi coatings showed uniform and rough surfaces. For Phase 1, roughness was evaluated as fine, medium, and coarse. The eSEM image analysis and cell counting by DAPI demonstrated that hMSCs have a tendency to form stronger adhesion and greater pseudopodia extensions on fine roughness surfaces. Individual hMSCs were seen forming cytoplasmic processes extending across the width of a pore. There was a 4- and 20-fold reduction in adhered hMSCs with an increase to medium and coarse roughnesses, respectively. For Phase 2, studied groups are (1) medium CPTi coating with zirconia polishing, (2) medium CPTi coating with CPTi polishing, and (3) fine CPTi coating with CPTi polishing. The eSEM image analysis and cell counting by DAPI demonstrated that hMSCs have a tendency to form stronger adhesion and greater pseudopodia extensions on Group 3 over the other two groups. There was a twofold reduction in adhered hMSCs on medium roughness relative to fine. No difference in cell adhesion was found between Groups 1 and 2. Individual hMSCs were seen forming cytoplasmic processes extending across the width of a pore. ConclusionsPreviously, it was accepted without much scrutiny that surface coatings were beneficial. This study begins to discover that surface topography directly affects the potential for cells to adhere and proliferate and lead to greater surgical efficacy.

ALA-PDT elicits oxidative damage and apoptosis in UVB-induced premature senescence of human skin fibroblasts

Background5-Aminolevulinic acid photodynamic therapy (ALA-PDT) has been used for the treatment of skin photoaging. It can significantly improve the appearance of fine lines, dotted pigmentation, and roughness of photoaged skin. However, the mechanisms by which ALA-PDT yields rejuvenating effects on photoaged skin have not been well elucidated. Thus, in this study we explored the effects of ALA-PDT in photoaged fibroblasts. MethodsWe established a stress-induced premature senescence (SIPS) model by repeated exposures of human dermal fibroblasts (HDFs) to ultraviolet B (UVB) irradiation. Cells were irradiated by red light laser at 635nm wavelength (50mW/cm2). Intracellular protoporphyrin IX (PpIX) was detected by confocal microscopy. Intracellular reactive oxygen species (ROS) level and mitochondrial membrane potential (MMP) change were detected by fluorescence microscopy and flow cytometry. Morphological changes were observed by optical microscopy. Proliferative activity was measured by a cell counting kit-8 (CCK-8). Cell apoptosis was detected by fluorescence microscopy using Hoechst staining and flow cytometry using annexin V/propidium Iodide double staining. ResultsIntracellular PpIX fluorescence in UVB-induced premature senescent HDFs (UVB-SIPS-HDFs) reached the highest intensity after incubation with 1.00mmol/L ALA for 6h (P<0.05). Compared with control group, intracellular ROS level, MMP, and apoptotic rate were increased (P<0.05) and proliferative activity was decreased (P<0.05) in UVB-SIPS-HDFs treated with ALA-PDT, which were positively correlated to ALA incubation time and red light laser dose. ConclusionOur study demonstrated that ALA-PDT elicits oxidative damage and apoptosis in photoaged fibroblasts in vitro, which may be the basis for the rejuvenating effects on photoaged skin.

Fatigue crack propagation properties of submicron-thick freestanding copper films in vacuum environment

Fatigue crack propagation experiments were conducted in approximately 500 nm thick freestanding copper (Cu) films in both air and vacuum environments to clarify the effects of vacuum environment on fatigue crack propagation properties. First, we newly developed an experimental setup for fatigue crack propagation experiments of the freestanding Cu films inside a vacuum chamber of a field-emission scanning electron microscope (FESEM). Fatigue crack propagation experiments were conducted in ambient air and vacuum environment of the FESEM chamber (˜10-4 Pa) under load-control conditions with constant maximum stress and at a stress ratio R of 0.1. In situ FESEM observations of fatigue crack propagation confirmed that preceding intrusions/extrusions were formed ahead of the fatigue crack tip, and the fatigue crack then propagated preferentially through these intrusions/extrusions in the lower stress intensity factor range (ΔK). In the higher ΔK, the fatigue crack propagated in tensile fracture mode. These mechanisms of fatigue crack propagation were similar to those in air. The relationships between fatigue crack propagation rate (da/dN) and stress intensity factor range (ΔK) in both environments were roughly within a narrow band in the region of ΔK ≳ 4—5 MPam1/2. On the other hand, da/dN in vacuum became smaller than that in air in the region of ΔK ≲ 4—5 MPam1/2. FESEM observations confirmed that the fracture surfaces morphologies depended on the environments in ΔK ≲ 4—5 MPam1/2: flat fracture surface were mainly observed in air, whereas, in vacuum environment, blunt fracture surface with fine roughness were mainly observed. This suggests that reversible cyclic slip deformation and rewelding occurred in vacuum environments, resulting in smaller da/dN in vacuum than air.