A comprehensive review on application of atomic force microscopy in Forensic science.

The primary objective of forensic investigation of a case is to recognize, identify, locate, and examine the evidence. Microscopy is a technique that provides crucial information for resolving a case or advancing the investigation process by analyzing the evidence obtained from a crime scene. It is often used in conjunction with suitable analytical techniques. Various microscopes are employed; scanning probe microscopes are available in diverse forensic analyses and studies. Among these, the atomic force microscope (AFM) is the most commonly used scanning probe technology, offering a unique morphological and physico-chemical perspective for analyzing multiple pieces of evidence in forensic investigations. Notably, it is a non-destructive technique capable of operating in liquid or air without complex sample preparation. The article delves into a detailed exploration of the applications of AFM in the realms of nanomechanical forensics and nanoscale characterization of forensically significant samples.

An Experimental Study in Laser-Assisted Machining of AerMet100 Steel.

To solve the problems of poor surface quality and low tool life in conventional machining (CM) of AerMet100 steel, an experimental study was conducted in laser-assisted machining (LAM) of AerMet100 steel. The effects of laser power, cutting speed, feed rate, and depth of cut on the surface roughness of AerMet100 steel were studied based on a single-factor experiment. The degree of influence of each factor on the surface roughness was evaluated by analyses of variance and range in the orthogonal experiment, and the combination of process parameters for the optimal surface roughness was obtained. The order of influence was as follows: laser power > cutting speed > depth of cut > feed rate; the optimal combination of process parameters was laser power 200 W, cutting speed 56.5 m/min, feed rate 0.018 mm/rev, and depth of cut 0.3 mm. Compared to CM, the surface morphology of the workpiece under the optimization of LAM was relatively smooth and flat, the surface roughness Ra was 0.402 µm, which was reduced by 62.11%, the flank wear was reduced from 208.69 µm to 52.17 µm, there were no tipping or notches, and the tool life was significantly improved. The study shows that the LAM of AerMet100 steel has obvious advantages in improving surface quality and reducing tool wear.

The Influence of Laser Remelting Parameters on the Surface Quality of Copper.

In order to improve the surface quality of copper after laser remelting, this article took laser frequency, pulse width, and energy density as the research objects and used scanning electron microscopy (SEM), a laser confocal three-dimensional measurement instrument, hardness tester, and friction and wear measurement instrument to study the surface morphology, surface roughness, microhardness, and wear resistance of copper, respectively. The results indicate that the frequency, pulse width, and energy density of laser remelting could directly affect the surface quality of the sample, but the influence of frequency and pulse width was more significant. When the laser remelting frequency was 10 Hz, the pulse width was 10 ms, and the energy density was 132.69 J/mm2, the sample exhibited good surface morphology, roughness, and wear resistance. The relevant research in this article can provide a good reference for the laser surface treatment of copper-based materials.

Aging effect on surface chemistry and sorption properties of atmospheric pressure plasma treated lignocellulosic jute fibers.

Jute fibers are characterized by a heterogeneous chemical composition (cellulose and non-cellulosic components) and a complex layered structure with a hydrophobic surface outer layer responsible for their low wettability. In this work, after the removal of water-soluble components, raw jute fibers were subjected to atmospheric pressure dielectric barrier discharge (DBD) under different conditions (at 150 or 300 Hz) to tailor jute fiber surface structure and wettability. The research was focused on the aging effect during natural aging in a standard atmosphere investigated up to three weeks after DBD treatment. Alterations in the surface morphology of DBD-treated jute fibers were investigated by FE-SEM and AFM, while ATR-FTIR, XPS, and electrokinetic measurements were used to assess the changes in the jute fiber surface chemistry. Sorption properties were monitored through wetting time and capillary rise measurements. The sorption properties of DBD-treated jute fibers were improved (about 100 times lower wetting time and 15 % higher capillary rise height in comparison to untreated) due to the changes in surface chemistry (decreased lignin and hemicellulose content in parallel with cellulose oxidation) and morphology (about 4.6 times higher average roughness). The electrokinetic and sorption properties measurement confirmed the significance of aging effects in lignocellulosic fibers' functionalization using plasma.

Experimental Parametric Investigation of Nanosecond Laser-Induced Surface Graphitization of Nano-Crystalline Diamond.

While nano-crystalline diamond (NCD) is a promising engineering composite material for its unique mechanical properties, achieving the ultrahigh surface quality of NCD-based components through conventional grinding and polishing is challenging due to its exceptional hardness and brittleness. In the present work, we experimentally investigate the nanosecond laser ablation-induced graphitization characteristics of NCD, which provides a critical pretreatment method of NCD for realizing its superlative surface finish. Specifically, systematic experimental investigations of the nanosecond pulsed laser ablation of NCD are carried out, in which the characteristics of graphitization are qualitatively characterized by the Raman spectroscopy detection of the ablated area of the microhole and microgroove. Subsequently, the influence of laser processing parameters on the degree and morphological characteristics of graphitization is evaluated based on experimental data and related interpretation, from which optimized parameters for maximizing the graphitization of NCD are then identified. The findings reported in the current work provide guidance for promoting the machinability of NCD via laser irradiation-induced surface modification.

Characterization of Micro-Threaded Stem Taper Surfaces of Cementless Hip Endoprostheses.

We investigated micro-threaded stem taper surface and its impact on premature failures, aseptic loosening, and infection in cementless hip endoprostheses. Our study focused on the fretting, and crevice corrosion of micro-threaded tapers, as well as the characterization of the microstructure and surface properties of two new and three retrieved Zweymüller stem tapers. The retrieved samples were selected and examined based on the head-stem taper interface being the sole source of modularity with a metallic component, specifically between the Ti alloy taper stem and the ceramic head. To determine the surface chemistry and microstructures of both new and retrieved hip endoprostheses stem taper titanium alloy, scanning -electron microscopy (SEM) was employed for morphological and microstructural analyses. Energy dispersive spectroscopy (EDS) was utilized for characterizing chemical element distribution, and electron backscattered diffraction (EBSD) was used for phase analysis. The roughness of the micro-threated stem tapers from different manufacturers was investigated using an optical profilometer, with standard roughness parameters Ra (average surface roughness) and Rz (mean peak to valley height of the roughness profile) being measured. Electrochemical studies revealed no fretting corrosion in retrieved stem tapers with ceramic heads. Consequently, three retrieved tapers and two new ones for comparison underwent potentiodynamic measurements in Hank's solution to determine the corrosion rate of new and retrieved stem taper surfaces. The results showed a low corrosion rate for both new and prematurely failed retrieved samples due to aseptic loosening. However, the corrosion rate was higher in infected and low-grade infected tapers. In conclusion, our study suggests that using ceramic heads reduces taper corrosion and subsequently decreases the incidence of premature failures in total hip arthroplasty.

Effect of GaN Cap Thickness on the DC Performance of AlGaN/GaN HEMTs.

We prepared AlGaN/GaN high electron mobility transistors (HEMTs) with GaN cap thicknesses of 0, 1, 3, and 5 nm and compared the material characteristics and device performances. It was found that the surface morphology of the epitaxial layer was effectively improved after the introduction of the GaN cap layer. With the increase of the GaN cap thickness, the carrier concentration (ns) decreased and the carrier mobility (µH) increased. Although the drain saturation current (IdSat) of the device decreased with the increasing GaN cap thickness, the excessively thin GaN layer was not suitable for the cap layer. The thicker GaN layer not only improved the surface topography of the epitaxial layer but also effectively improved the off-state characteristics of the device. The optimal cap thickness was determined to be 3 nm. With the introduction of the 3 nm GaN cap, the IdSat was not significantly reduced. However, both the off-state gate leakage current (IgLeak) and the off-state leakage current (IdLeak) decreased by about two orders of magnitude, and the breakdown voltage (BV) increased by about 70 V.

Discoloration and Surface Changes in Spruce Wood after Accelerated Aging.

Spruce wood is widely used in outdoor applications, but its susceptibility to degradation under exposure to sunlight and moisture is a major concern. This study investigates the impact of accelerated aging on spruce wood's surface chemistry, microstructure, geometry, and discoloration. The study was performed in two outdoor aging modes: dry and wet. The accelerated aging effects were evident in the changes in spruce wood structure, as well as in the other studied properties. During aging, it developed significant discoloration. Under simulated rainless outdoor conditions (dry mode), spruce wood gradually became dark brown. Under conditions involving rain (wet mode), the discoloration was qualitatively different from the dry mode. FTIR spectroscopy showed that during the accelerated aging of wood, lignin was mainly degraded, especially in the early stages of the process. A linear correlation was found between the changes in lignin and the color changes in the wood. There was an increase in carbonyl groups in the dry mode, which contributed to the color change and was also influenced by changes in extractives. The wet mode caused the leaching out of carbonyl groups. The observed decrease in cellulose crystallinity, together with the degradation of hydrophobic lignin, may result in the increased hydrophilicity of photodegraded wood. For both modes, there were different changes in the wood micro- and macrostructure, reflected in the surface morphology. The roughness increased during the aging process in both modes. The slightest changes in the roughness parameters were identified in the grain direction in the dry mode; the most evident was that the roughness parameters increased perpendicular to the grain in the wet mode. The demonstrated mechanism backing up the aging-related changes to the spruce wood structure and the relations unveiled between these changes and the changes in the spruce wood surface properties can provide an issue point for seeking ways how to mitigate the negative effects of the environmental factors the wood is exposed to.

Characterizing Surface Morphological and Chemical Properties of Commonly Used Orthopedic Implant Materials and Determining Their Clinical Significance.

The goal of the study was to compare the surface characteristics of typical implant materials used in orthopedic surgery and traumatology, as these determine their successful biointegration. The morphological and chemical structure of Vortex plate anodized titanium from commercially pure (CP) Grade 2 Titanium (Ti2) is generally used in the following; non-cemented total hip replacement (THR) stem and cup Ti alloy (Ti6Al4V) with titanium plasma spray (TPS) coating; cemented THR stem Stainless steel (SS); total knee replacement (TKR) femoral component CoCrMo alloy (CoCr); cemented acetabular component from highly cross-linked ultrahigh molecular weight polyethylene (HXL); and cementless acetabular liner from ultrahigh molecular weight polyethylene (UHMWPE) (Sanatmetal, Ltd., Eger, Hungary) discs, all of which were examined. Visualization and elemental analysis were carried out by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Surface roughness was determined by atomic force microscopy (AFM) and profilometry. TPS Ti presented the highest Ra value (25 ± 2 µm), followed by CoCr (535 ± 19 nm), Ti2 (227 ± 15 nm) and SS (170 ± 11 nm). The roughness measured in the HXL and UHMWPE surfaces was in the same range, 147 ± 13 nm and 144 ± 15 nm, respectively. EDS confirmed typical elements regarding the investigated prosthesis materials. XPS results supported the EDS results and revealed a high % of Ti4+ on Ti2 and TPS surfaces. The results indicate that the surfaces of prosthesis materials have significantly different features, and a detailed characterization is needed to successfully apply them in orthopedic surgery and traumatology.

On the role of surface morphology in impacting-freezing dynamics of supercooled droplets.

A thorough understanding of droplet impact and freezing is vital in preventing ice accretion on many outdoor devices. This simulation-based study investigated the effect of surface morphology on the impacting-freezing process of a supercooled droplet. Also, the variations of Weber number and supercooling temperature were studied numerically. The droplet impact and freezing process were simulated with the volume of fluid method and freezing model. A more accurate simulation was achieved by modeling the supercooled droplet and the dynamic contact angle. At the given ranges of the input parameters, the main factors that guaranteed droplet rebounding after collision were determined. The supercooling temperature and the groove width should be above 266 K and less than 0.21 mm, respectively. The droplet should also maintain its cohesion and integrity during impact. Creating grooves on a surface is novel and paves a new way to understand the impact and solidification of water droplets in supercooled conditions.

In vitro digestion of microplastics in human digestive system: Insights into particle morphological changes and chemical leaching.

Despite the well-reported occurrences and established pathways for microplastics (MPs) ingestion by humans, the eventual fate of these particles in the human gastrointestinal system is poorly understood. The present study tries to gain a better understanding of the fate of four common food-borne MPs, i.e. Polystyrene (PS), Polypropylene (PP), Low-density Polyethylene (LDPE), and Nylon, in a simulated in vitro human digestive system. Firstly, the changes in the physicochemical properties of 20-210 µm sized MPs as well as the leaching of chemicals were monitored using fluorescence microscopy, FTIR, and LC-QTOF-MS. Thereafter, the mass loss and morphological alterations in 3-4 mm sized MPs were observed after removing the organic matter. The interaction of PS and PP MPs with duodenal and bile juices manifested in a corona formation. The increase in surface roughness in PP MPs aligned with MP-enzyme dehydrogenation reactions and the addition of NO groups. A few fragments ranging from 30 to 250 µm, with negligible mass loss, were released during the MP digestion process. In addition, the leaching of compounds, e.g. capsi-amide, butanamide, and other plasticizers and monomers was also observed from MPs during digestion, and which may have the potential to accumulate and get absorbed by the digestive organs, and to subsequently impart toxic effects.

Influence of Etchants on Etched Surfaces of High-Strength and High-Conductivity Cu Alloy of Different Processing States.

With the continuous integration of semiconductor devices, the requirements of the size accuracy and surface quality of etched lead frames are stricter. The etchant is a key factor in the etching process and etched surface quality, while the effects of the difference in etchants on the etched surface morphology of Cu alloy have not been directly studied. In this study, aqua regia, acidic FeCl3 and two CuCl2 solutions were used as etchants, and different CuCrSn specimens were etched and characterized. The results show that the etching rate in aqua regia is high, and the grain orientation, grain boundary (GB) and dislocations have significant influences on the local etching rate. The preferential etching of some atomic planes forms steps between the grains with different orientations, and preferential etching around the GB and dislocation group forms grooves, resulting in high surface roughness. For the surfaces etched by the FeCl3 and CuCl2 etchants, the steps and grooves are blurred; thus, they are less rough. The CuCrSn alloy surface etched by the aqua regia is clean, with little Cr-rich particles, while high-density Cr-rich particles remain on the surfaces etched by the FeCl3 and CuCl2 etchants. For the same kind of etchant, the ion concentration can affect the etching mechanism, rate and the etched surface morphology.

Electrospun Poly-l-Lactic Acid Membranes Promote M2 Macrophage Polarization by Regulating the PCK2/AMPK/mTOR Signaling Pathway.

Electrospun membranes are widely used in tissue engineering. Regretfully, there is limited research on how its morphological characteristics precisely regulate macrophage activation and immune response. Therefore, electrospun poly-l-lactic acid (PLLA) membranes with different alignments (align and random) and diameters (nanoscale and microscale) are prepared to investigate the effects of different surface morphologies on M2 macrophage polarization. Additionally, transcriptome, proteome, and phosphoproteome sequencings are combined to examine the underlying regulatory mechanisms. The results show that the electrospun PLLA membranes with different surface morphologies have good biocompatibility and can regulate the phenotype and function of macrophages by changing the micromorphology of the matrix surface. Especially, macrophages cultured on the electrospun membranes of the A600 group exhibit higher M2 macrophage polarization than the other three groups. Furthermore, the findings demonstrate that electrospun PLLA membranes enhance AMP-activated protein kinase (AMPK)/ mammalian target of rapamycin (mTOR) signaling activation by upregulating the expression of integrin phosphoenolpyruvate carboxykinase 2 (PCK2), which is critical for M2 macrophage polarization. Taken together, electrospun PLLA membranes promote M2 macrophage polarization by regulating the PCK2/AMPK/mTOR signaling pathway. This research can provide further theoretical bases for scaffold design, immunoregulatory mechanisms, and clinical application based on electrospinning technology in the future.

Effects of surface nanomorphology on the senescence of periodontal ligament stem cells.

OBJECTIVES: The effect of TiO2 nanotube morphology on the differentiation potency of senescent periodontal ligament stem cells was investigated. METHODS: Two types of titanium sheets with TiO2 nanotube morphology (20V-NT and 70V-NT) were prepared via anodic oxidation at 20 and 70 V separately, and their surface morphology was observed. Young periodontal ligament stem cells were cultivated in an osteogenic induction medium, and the most effective surface morphology in promoting osteogenic differentiation was selected. RO3306 and Nutlin-3a were used to induce the aging of young periodontal ligament stem cells, and senescent periodontal ligament stem cells were obtained. The osteogenic differentiation of senescent periodontal ligament stem cells was induced, and the effect of surface morphology on osteogenic differentiation was observed. RESULTS: Nanotube morphology was achieved on the surfaces of titanium sheets through anodic oxidation, and the diameters of the nanotubes increased with voltage. A significant difference in the effect of nanotube morphology was found among nanotubes with different diameters in the young periodontal ligament stem cells. The surface nanotube morphology of 20V-NT had a more significant effect that promoted osteogenic differentiation. Compared with a smooth titanium sheet, the surface nanotube morphology of 20V-NT increased the number of alkaline phosphatase-positive senescent periodontal ligament stem cells and promoted calcium deposition and the expression of osteogenic marker genes Runt-related transcription factor 2, osteopontin, and osteocalcin. CONCLUSIONS: A special nanotube morphology enhances the differentiation ability of senescent periodontal ligament stem cells, provides an effective method for periodontal regeneration, and further improves the performance of implants.

Effect of different surface roughening treatment on polyether ether ketone and acrylic resin bonding: A pilot study.

BACKGROUND: As polyether ether ketone (PEEK) is a relatively new material in dentistry, its bonding properties with regard to dental acrylic base materials are not fully known. To ensure the long-term success of removable dentures with a PEEK framework, the base materials must be well bonded to each other. OBJECTIVES: The study aimed to investigate the effects of different kinds of surface roughening treatment on PEEK and acrylic resin bonding. MATERIAL AND METHODS: Eighty PEEK specimens (N = 80) were randomly divided into 5 groups (n = 16 per group) and subjected to various surface roughening treatment (control, grinding, sandblasting, tribochemical silica coating (CoJet), and sulfuric acid etching). Heat-polymerized acrylic resin was applied to the treated surfaces of the PEEK specimens. The shear bond strength (SBS) test, environmental scanning electron microscopy (ESEM) analysis and three-dimensional (3D) surface topography analysis were performed. The statistical analysis of the data was conducted using the analysis of variance (ANOVA) and Tukey's multiple comparison test. RESULTS: The one-way ANOVA showed significant differences in the SBS values between the groups (p = 0.001). Sandblasting, tribochemical silica coating and sulfuric acid etching resulted in high SBS values (p = 0.001). The highest SBS values were observed in the sulfuric acid etching group (8.83 ±3.63 MPa), while the lowest SBS values were observed in the control group (3.33 ±2.50 MPa). CONCLUSIONS: The additional roughening treatment applied to the PEEK surface increases the bond strength with heat-polymerized acrylic resin.

Investigation of Perovskite Solar Cells Using Guanidinium Doped MAPbI3 Active Layer.

In this work, guanidinium (GA+) was doped into methylammonium lead triiodide (MAPbI3) perovskite film to fabricate perovskite solar cells (PSCs). To determine the optimal formulation of the resulting guanidinium-doped MAPbI3 ((GA)x(MA)1-xPbI3) for the perovskite active layer in PSCs, the perovskite films with various GA+ doping concentrations, annealing temperatures, and thicknesses were systematically modulated and studied. The experimental results demonstrated a 400-nm-thick (GA)x(MA)1-xPbI3 film, with 5% GA+ doping and annealed at 90 °C for 20 min, provided optimal surface morphology and crystallinity. The PSCs configured with the optimal (GA)x(MA)1-xPbI3 perovskite active layer exhibited an open-circuit voltage of 0.891 V, a short-circuit current density of 24.21 mA/cm2, a fill factor of 73.1%, and a power conversion efficiency of 15.78%, respectively. Furthermore, the stability of PSCs featuring this optimized (GA)x(MA)1-xPbI3 perovskite active layer was significantly enhanced.

Experimental Investigation on Diamond Band Saw Processing of Resin Mineral Composites.

Resin mineral composite (RMC) is a new material with several times the damping properties of gray cast iron and great corrosion resistance. Due to its overall brittleness, sawing with a diamond band saw would be a suitable method. In this research, sawing experiments are carried out to study the sawing force characteristics of the material and its surface morphology during the processing. The results show that the feed force level is in the range of 3.5~5.5 N and the tangential force level is relatively low. The distribution of resin mineral components does not have a significant impact on the average sawing force but increases the fluctuation of the lateral force signal. The maximum fluctuation volume is 94.86% higher than other areas. Uneven lateral force, generated when diamond particles pass through the resin-mineral interface, is one of the causes of fluctuations. The machined surface of RMC has uniform strip scratches and a small number of pits. Maintaining a constant ratio of sawing speed to feed speed can result in approximately the same machined surface. A step structure with a height of about 10 µm appears at the interface of resin minerals. As a processing defect, it may affect the performance of RMC components in some aspects, which need a further precision machining processing.

Understanding the Relationship between Surface Quality and Chip Morphology under Sustainable Cutting Environments.

Although chip morphology changes according to the machining method and related cutting parameters, chip formation affects the quality of the machined surface. In this context, it is very important to understand the relationship between chip morphology and surface quality, especially in materials that are difficult to machine. In the presented study, the changes in chip morphology, surface morphology, and surface quality criteria (Ra and Rz) that occurred during the milling of precipitation-hardened steel in different cutting environments were analyzed. Milling experiments were carried out in dry, MQL (minimum quantity lubrication), nano-MQL (graphene), nano-MQL (hBN), Cryo, and Cryo-MQL environments using TiAlN-coated inserts and three different cutting speeds and feed rates. While the highest values in terms of Ra and Rz were measured in dry machining, the minimum values were obtained in a nano-MQL (hBN) cutting environment. Due to the lubrication and low friction provided by the MQL cutting environment, chips were formed in thinner segmented forms. This formation reduced the chip curve radius and thus provided a more stable surface morphology. On the other hand, Cryo-ambient gas could not effectively leak into the cutting zone due to the intermittent cutting process, but it increased the brittleness of the chips with the cooling effect and provided a similar surface morphology. The values of minimum Ra and Rz were obtained as 0.304 mm and 1.825 mm, respectively, at a 60 m/min cutting speed and 0.04 mm/rev feed. Consequently, the use of nano-MQL cutting medium is seriously recommended in terms of surface quality in milling operations of difficult-to-machine materials.

Tunable evaporation-induced surface morphologies on chitosan film for light management.

The surface morphologies of polymer films have been used to improve the performance or enable new applications of films, such as controllable adhesion, shape morphing and light management. However, complicated and destructive methods were applied to produce surface morphologies on chitosan (CS) film. To overcome this challenge, we report an evaporation-induced self-assembly to form the tunable morphologies on the surface of short-chain chitosan film by varying the evaporation rates that influence the aggregation behavior of polymer chains between order and disorder. It enables the simple, tunable and scalable fabrication of surface morphologies on CS film (CS solution concentration: 2 wt%, drying from room temperature (RT) to 80 °C) that provides controllable haze (3-74 %) and high transmittance (>85 %) for the production of hazy and transparent window coatings. This simple approach to producing tunable surface morphologies could inspire the synthesis of multifunctional polymer films with different surface structures, whose applications can be extended to cell culture interfaces, flexible bioelectronic and optoelectronic devices.

A literature review of biomechanical studies on physiological and pathological sacroiliac joints: Articular surface structure, joint motion, dysfunction and treatments.

BACKGROUND: Sacroiliac joints are affected by mechanical environments; the joints are formed under mechanical stimulation, receive impact of walking between the upper and lower parts of the bodies and can be a cause of pain due to non-physiological loads. However, there are so far very few studies that reviewed biomechanics of physiological and pathological sacroiliac joints. This review article aims to describe the current sacroiliac joint biomechanics. METHODS: Previous original papers have been summarized based on three categories: articular surface structure, sacroiliac joint motion and sacroiliac joint dysfunction and treatments. FINDINGS: Although the articular surface morphologies vary greatly from individual to individual, many researchers have tried to classify the joints into several types. It has been suggested that the surface morphologies may not change regardless of joint dysfunction, however, the relationship between the joint structure and pain are still unclear. The range of sacroiliac joint motion is demonstrated to be less than 1 mm and there is no difference between physiological and pathological joints. The sacroiliac joint absorbs shock within the pelvis by the joint structures of pelvic morphology, ligaments and fat tissues. The morphology and motion of the sacroiliac joints may be optimized for upright bipedal walking. INTERPRETATION: There is no doubt that pelvic mechanical environments affect pain induction and treatment; however, no one has yet provided a concrete explanation. Future research could help develop treatments based on sacroiliac joint biomechanics to support joint function.