Revealing the Correlation between Molecular Structure and Corrosion Inhibition Characteristics of N-Heterocycles in Terms of Substituent Groups.

Controlling metal corrosion can directly address the waste of metal and the environmental pollution and resource depletion caused by metal recycling, very significant factors for green and sustainable development. The addition of corrosion inhibitors is a relatively cost-effective means of corrosion prevention. Among these, N-heterocycles have been widely used because heteroatoms contain lone pairs of electrons that can be strongly adsorbed onto metals, protecting them in highly corrosive environments at relatively low concentrations. However, due to the large variety of N-heterocycles, their corrosion inhibition characteristics have seldom been compared; therefore, the selection of appropriate N-heterocycles in the development of anti-corrosion products for specific applications was very difficult. This review systematically analyzed the influence of different substituents on the corrosion inhibition performance of N-heterocycles, including different alkyl chain substituents, electron-donating and electron-withdrawing substituents, and halogen atoms, respectively. The correlation between the molecular structure and corrosion inhibition characteristics of N-heterocycles was comprehensively revealed, and their action mechanism was analyzed deeply. In addition, the toxicity and biodegradability of N-heterocycles was briefly discussed. This study has provided a significant guideline for the development of green, promising corrosion inhibitors for advanced manufacturing and clean energy equipment protection.

Interfacial Adsorption and Corrosion Inhibition Behavior of Environmentally Friendly Imidazole Derivatives for Copper in the Marine Environment.

Copper and copper alloys are commonly used in industry due to their excellent mechanical properties, making research on the corrosion resistance of copper of great significance. The corrosion inhibition properties of 2-imidazolidinone and allantoin for copper in 3.5 wt % NaCl were studied by weight loss and electrochemical tests. Changes in the density of the copper corrosion current and the impedance module indicated that 2-imidazolidinone and allantoin exhibited cathodic corrosion inhibitors and a valid protective effect. Meanwhile, the weight loss tests showed that the inhibition efficiency of 2-imidazolidinone and allantoin at 3 mM reached 98.94% and 97.82%, respectively. The surface physiochemical properties were qualitatively and quantitatively studied by using SEM-EDS, XPS, white light interferometry, and contact angle analysis. The interfacial adsorption behavior revealed by QCM, synchrotron radiation micro-infrared, and adsorption isotherm analysis indicated that both imidazole derivatives formed an effective and rigid physical adsorption film and obeyed the Langmuir adsorption model on copper, while both the mass and thickness of the adsorption film formed by 2-imidazolidinone were higher than those of allantoin. This study contributed to an in-depth understanding of the interfacial adsorption behavior and corrosion inhibition ability of 2-imidazolidinone and allantoin and provided guidelines for the design and development of novel heterocycles as potential corrosion inhibitors for copper in marine environments. In particular, copper was used as a corrosion inhibitor in seawater storage and transport equipment.

Study on the Liquid-Liquid and Liquid-Solid Interfacial Behavior of Functionalized Graphene Oxide.

With the rise of carbon neutrality, the applications of carbon-based materials are gaining considerable attention. Graphene oxide (GO) is a two-dimensional sheet with epoxy and hydroxyl groups on the basal plane and carboxyl groups at the edge. In order to change the oil/water (o/w) interfacial activity, GO was controlled and modified by dodecylamine to get two kinds of functionalized GOs (fGOs), named as basal plane-functionalized GO (bGO) and edge-functionalized GO (eGO), respectively. The interfacial tension measurement showed that fGOs could reduce more interfacial tension at the poly-α-olefin/water interface than those at synthetic esters or aromatic compounds/water interfaces. Besides, eGO can reduce more poly-α-olefin-4/water interfacial tension compared to bGO. The interfacial dilatational rheology of eGO and fatty alcohol polyoxyethylene ether-4 (MOA4) showed that MOA4 gradually replaced eGO at the interface with the increase of MOA4, until the interface was completely occupied. eGO and MOA4 complex emulsion exhibited the best friction-reducing performance at 250 rpm. The coefficient of friction (COF) curves of the emulsions with eGO showed two platforms, with the COF reduced by 37.42% at the most. The rheological results of emulsions showed that the addition of eGO increased the elasticity of the emulsion. Emulsions showed shear-thinning and friction-thickening properties, which make it easier for the emulsion to form a lubricating film on the metal surface. Our research results suggested that the functionalization on the edge of GO will change the interfacial properties significantly, which have widespread applications in the encapsulation of active materials, surface protection, adsorption, and separation of pollutants.

Highly Sensitive Flexible Tactile Sensor Mimicking the Microstructure Perception Behavior of Human Skin.

A 3D printed flexible tactile sensor with graphene-polydimethylsiloxane (PDMS) microspheres for microstructure perception is presented. The structure of the tactile sensor is inspired by the texture of the human finger and is designed to enable the detection of various levels of surface roughness via the processing of tactile signals. The tactile sensor with a unique graphene-PDMS microsphere structure shows excellent comprehensive mechanical properties, including a robust stretching ability (elongation at break of the sensing layer is 70%), excellent sensing ability (short response time of 60 ms), high sensitivity (sensitivity up to 2.4 kPa-1), and cycle stability (over 2000 loading cycles). In addition, such versatility and sensitivity allow the electronic skin not only to accurately monitor pressure but also to distinguish various surface topographies with microscale differences, and to detect the action of an air fluid.

Erratum: A novel vehicle-like drug delivery 3D printing scaffold and its applications for a rat femoral bone repairing in vitro and in vivo: Erratum.

[This corrects the article DOI: 10.7150/ijbs.37552.].

A novel 3D printed bioactive scaffolds with enhanced osteogenic inspired by ancient Chinese medicine HYSA for bone repair.

Some traditional Chinese medicine (TCM) has been applied in bone repair, however, hydroxy-safflower yellow A (HYSA), one composition of safflower of the typical invigorating the circulation of TCM, has little been studied in orthopedics field for osteogenesis and angiogenesis clinically. Herein, we hypothetically speculated that the synthetic bioactive glasses (BG, 1393) scaffolds carried HYSA by a 3D print technique could enhance osteogenic repair properties. Notably, scaffolds coating chitosan/sodium alginate endowed with excellent drug control release ability, and significantly improved the BG mechanical strength. HYSA was loaded into BG scaffolds by coating chitosan/sodium alginate film, and the osteogenesis and angiogenesis of the HYSA/scaffolds were evaluated in vitro and in vivo. In vitro the cell culture results exhibited that the high dose of HYSA (0.5 mg/ml) loaded scaffolds can promote the proliferation of bone marrow stromal cells (rBMSCs) and migration, tubule formation of human umbilical vein endothelial cells (HUVECs). The active alkaline phosphatase (ALP) of rBMSCs can also be improved by the high dose of HYSA/scaffolds. Results of qRT-PCR and Western blot indicated that the high dose of HYSA/scaffolds can up-regulate ALP, OCN, OPN and RUNX-2 expression and relative protein secretion of the HIF-1α and BMP-2. In the animal experiment, the high dose of HYSA/scaffolds has a significantly better capacity to promote new bone formation than the undoped scaffolds at 8 weeks post-surgery. Thus, our results claimed that the novel HYSA/scaffolds hold the substantial potential to be further developed as effective and safe bone tissue engineering biomaterials for bone regeneration by combining enhanced osteogenesis and angiogenesis.

Friction stability and cellular behaviors on laser textured Ti-6Al-4V alloy implants with bioinspired micro-overlapping structures.

The grain structure and surface morphology of bio-implants act as a pivotal part in altering cell behavior. Titanium alloy bone screws, as common implants, are prone to screws loosening and complications threat in the physiological environment due to their inferior anti-wear and surface inertia. Manufacturing bone screws with high wear resistance and ideal biocompatibility has always been a challenge. In this study, a series of overlapping morphologies inspired by the hierarchical structure of fish scales and micro bulges of shrimp were structured on Ti-6Al-4V implant by laser texturing. The results indicate that the textured patterns could improve cell attachment, proliferation, and osteogenic differentiation. The short-term response of human bone marrow-derived mesenchymal stem cells (hBMSCs) on the textured surface are more sensitive to the microstructure than the surface roughness, wettability, grain size and surface chemical elements of the textured surfaces. More importantly, the friction-increasing and friction-reducing type overlapping structures exhibit excellent friction stability at different stages of modified simulated body fluid (m-SBF) soaking. The overlapping structure (Micro-smooth stacked ring: MSSR) is more beneficial to promote the formation of apatite. Deposited spherical-like apatite particles can act as a "lubricant" on the MSSR surface during the friction process to alleviate the adhesion wear of the surface. Meanwhile, apatite particles participate in the formation of friction film, which plays an effective role in reducing friction and antiwear in corrosion solution (m-SBF) for a long time. These features show that the combination of soaking treatment in m-SBF solution with laser-textured MSSR structure is expected to be an efficient and environmentally friendly strategy to prolong the service life of bone screws and reducing the complications of mildly osteoporotic implants.

A novel vehicle-like drug delivery 3D printing scaffold and its applications for a rat femoral bone repairing in vitro and in vivo.

The high surface area ratio and special structure of mesoporous bioactive glass (MBG) endow it with excellent physical adsorption of various drugs without destroying the chemical activity. Silicate 1393 bioactive glass (1393) is famous for its fantastic biodegradability and osteogenesis. Herein, we have built a novel vehicle-like drug delivery 3D printing scaffold with multiplexed drug delivery capacity by coating MBG on the surface of 1393 (1393@MBG). Furthermore, we have applied DEX and BMP-2 on the 1393@MBG scaffold to endow it with antibacterial and osteogenic properties. Results indicated that this 1393@MBG scaffold could effectively load and controlled release BMP-2, DNA and DEX, which can be applied for orthopedic treatment. The in vitro study showed that the DEX loaded 1393@MBG exhibited excellent antibacterial ability, which was evaluated by Staphylococcus aureus (S. aureus), and the BMP-2 loaded 1393@MBG can improve the alkaline phosphatase (ALP) activity and upregulate the expression of osteogenesis-related genes (OCN and RUNX2) of human bone mesenchymal stem cells (hBMSCs). Moreover, the in vivo study further confirmed that the BMP-2 loaded 1393@MBG group showed better osteogenic capacity as compared to that of the 1393 group in a rat femoral defect. Together, these results suggested that the vehicle-like drug delivery 3D printing scaffold 1393@MBG could be a promising candidate for bone repair and relative bone disease treatment.

Alkyl-Ethylene Amines as Effective Organic Friction Modifiers for the Boundary Lubrication Regime.

With the pursuit of fuel economy in the automotive industry, recently low-viscosity lubricant technology has been widely improved. The present work has systematically discussed a series of sulfur- and phosphorus-free organic friction modifiers (FMs)-alkyl-ethylene amines-by alkyl substitution from ethylene amines with various nitrogen-atom numbers and molecular configurations. Herein, the pin-on-flat reciprocation friction tests have exhibited that the addition of the novel alkyl-ethylene amines into base oil led to significant reductions in the friction coefficient (up to 23%). Further investigations of tribological properties at elevated temperatures demonstrated that the increased number of nitrogen atoms and the regular linear atomic arrangement contributed to an improvement of friction reduction (up to 66%) compared to the neat base oil. Notably, results of water contact angle measurement and infrared spectroscopy (IR) have provided favorable evidence that the novel FMs have adsorbed on the metal surface leading to the formation of a tribofilm, whereby the tribofilm prevented the sliding surfaces from direct asperity contact and markedly improved the tribological performance, as seen from the composition analysis of the worn surfaces by an energy-dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), and confocal Raman spectroscopy. Therefore, the present work can provide a practical reference for molecular structure design through investigation of structure-performance relations of lubricant additives.

Nitrogen-doped carbon fibers embedding CoOx nanoframes towards wearable energy storage.

As continuous consumption of the world's lithium reserves is causing concern, alternative energy storage solutions based on earth-abundant elements, such as sodium-ion batteries and zinc-air batteries, have been attracting increasing attention. Herein, nanoframes of CoOx are encapsulated into carbonized microporous fibers by electrospinning zeolitic imidazolate frameworks to impart both a sodium-hosting capability and catalytic activities for reversible oxygen conversion. The ultrahigh rate performance of sodium-ion batteries up to 20 A g-1 and ultrastable cycling over 6000 cycles are attributed to a dual-buffering effect from the framework structure of CoOx and the confinement of carbon fibers that effectively accommodates cyclic volume fluctuation. Both in situ Raman and ex situ microscopic analyses unveil the reversible conversion of CoOx during the sodiation/desodiation process. The excellent ORR activity, superior to that of commercial Pt/C, is mainly ascribed to the abundant Co-N-C species and the full exposure of active sites on the microporous framework structure. Flexible and rechargeable sodium-ion full batteries and zinc-air batteries are further demonstrated with great energy efficiency and cycling stability, as well as mechanical deformability.

Redox-Driven Lithium Perfusion to Fabricate Li@Ni-Foam Composites for High Lithium-Loading 3D Anodes.

As the hostless nature of the conventional Li anodes with planar surfaces inevitably causes volume expansion and parasitic dendrite growth, it is essential to develop a composite electrode structure with improved Li plating/stripping behaviors to mitigate such issues. Herein, a composite Li@NF anode was successfully fabricated through lithium perfusion into the commercial nickel foam (NF) decorated with lithiophilic NiO nanosheets, demonstrating an exceptionally high areal Li loading of 53.2 mg cm-2 with suppressed Li dendrite formation and volume expansion, improved Coulombic efficiency, as well as extended cycling stability in all half, symmetric, and full cell tests. More importantly, density functional theory calculations and control studies with Fe2O3@NF, pristine NF, and Cu2O@CF reveal a linear correlation between the thermodynamics of the surface reactions and the lithiophilicity of the reaction products, attesting to a redox-driven Li perfusion process. Further, through ex situ scanning electron and in situ optical microscopy, the enhanced performance of Li@NF is mainly attributed to the mediation of Li plating/stripping through homogenizing the Li+ flux, decentralizing local charge density, and accommodating multidirectional Li deposition by the conductive 3D scaffolds. Consequently, this study offers important insights into the driving of thermal Li perfusion through appropriate material and surface design for achieving safe and stable lithium metal anodes.

Enhanced Osseointegration of Titanium Alloy Implants with Laser Microgrooved Surfaces and Graphene Oxide Coating.

Rapid and effective osseointegration, as a critical factor in affecting the success rate of titanium (Ti) implants in orthopedic applications, is significantly affected by their surface microstructure and chemical composition. In this work, surface microgrooved Ti-6Al-4V alloys with graphene oxide coating (Ti-G-GO) were fabricated by a combination of laser processing and chemical assembly techniques. The osteogenic capability in vitro and new bone formation in vivo of the implants were systematically investigated, and biomechanical pull-out tests of the screws were also performed. First, in vitro studies indicated that the optimal microgroove width of the titanium alloy surface was 45 µm (Ti-G), and the optimum GO concentration was 1 mg/mL. Furthermore, the effects of the surface microstructure and GO coating on the in vitro bioactivity were investigated through culturing bone marrow mesenchymal stem cells (BMSCs) on the surface of titanium alloy plates. The results showed that the BMSCs cultured on the Ti-G-GO group exhibited the best adhesion, proliferation, and differentiation, compared with that on the Ti-G and Ti groups. Micro-computed tomography evaluation, histological analysis, and pull-out testing demonstrated that both Ti-G and Ti-G-GO implants had the higher osseointegration than the untreated Ti implant. Moreover, the osteogenic capability of the Ti-G-GO group appeared to be superior to that of the Ti-G group, which could be attributed to the improvement of surface wettability and apatite formation by the GO coatings. These results suggest that the combination of the microgroove structure and GO coatings exhibits considerable potential for enhancing the surface bioactivation of materials, and the combination modification is expected to be used on engineered titanium alloy surfaces to enhance osseointegration for orthopedic applications.

Chemically and physically cross-linked polyvinyl alcohol-borosilicate gel hybrid scaffolds for bone regeneration.

The composite scaffolds of bioactive glasses and polymers are often used in bone regeneration which could improve the stiffness, compressive strength and bioactivity of polymers while maintaining the osteoconductivity and osteoinductivity of bioactive glasses. But due to complicated situations and limitations of compositing process, the prepared composite materials have low uniformity and obvious phase separation, leading to problems such as poor mechanical properties and inferior new bone formation capacity. In this paper, a modified sol-gel processing technique was used to realize the homogeneous inorganic-organic composites. After hydrolysis of the metal alkoxide, the sol was mixed with the aqueous solution of polyvinyl alcohol (PVA), and through gelation and chemical reaction, the mixture was solidified into the inorganic-organic composite hydrogel. The composites showed as a uniform single phase with interpenetrating networks of PVA gel and borosilicate gel (BG) that chemically and physically interacted at the scale of molecular or nanometer, therefore PVA-BG hybrids were obtained. When immersed in phosphate-buffered saline, the PVA-BG hybrid-derived scaffolds released beneficial ions into the medium and converted to hydroxyapatite. The scaffolds were not toxic to the rat bone marrow-derived mesenchymal stem cells (rBMSCs), and supported rBMSCs proliferation. Furthermore, the alkaline phosphatase activity of the rBMSCs and the expression levels of osteogenic-related genes (alkaline phosphatase, osteocalcin and runt-related transcription factor 2) increased significantly with increasing amount of BG in the hybrid scaffolds. Finally, the bone defect repair results of critical-sized femoral condyle defect rat model demonstrated that PVA-BG hybrid scaffolds could enhance bone regeneration compared with PVA scaffolds. The results suggested that PVA-BG hybrid scaffolds may be a promising biomaterial for bone regeneration.

Interfacial Assembly Behavior of Alkylamine-Modulated Graphene Oxide with Different Oxidation Degrees.

Multitudinous studies have been carried out on the controllable functionalization and performance evaluation of graphene oxide (GO). In this study, the correlation between the amount of grafted alkylamine on GO and its interfacial assembly behavior at liquid-liquid and liquid-solid interfaces was studied. GO was modified with n-octylamine through basal functionalization (bGO). The grafting amount of alkylamines was regulated using two GOs varied in oxidation degree (GO_L and GO_H). A study on the oil-water interfacial behaviors shows that bGO_L has better ability to modulate the interfacial tension than that of bGO_H. Grafting alkylamine on GO will not only increase the interaction strength with oil while weaken that with water but also do damage to the graphene lattice and weaken the interaction of π-π stacking; therefore, bGO_L displays a broader capability to modulate interfacial tensions than that of bGO_H. The bGO-based Pickering emulsion was prepared, and the interfacial behavior at the liquid-solid interface was investigated. A study on the interfacial anti-rust performances demonstrates that grafted alkyl chains in bGOs can form more compact and ordered protective films on the metal surface and enhance the hydrophobicity as a result of the similar structure to oil in the emulsion system, which makes Pickering emulsions show better anti-rust abilities than water dispersions. Meanwhile, the bGO_H emulsion shows a better anti-rust property than that of the bGO_L emulsion. A study on the interfacial tribological behaviors shows that the lubricity of bGO_L is better than that of bGO_H. X-ray photoelectron spectroscopy analysis shows that a high content of C-O-C/C-OH in lubricating films contributes to the improvement of lubricity. The modulated interfacial assembly properties of GO at both liquid-liquid and solid-liquid interfaces suggest their potential applications in surface protection, lubrication, controllable drug deliveries, absorption and separation, nanocomposites, and catalyst fields.

Hypoxia-Mimicking Cobalt-Doped Borosilicate Bioactive Glass Scaffolds with Enhanced Angiogenic and Osteogenic Capacity for Bone Regeneration.

The osteogenic capacity of synthetic bone substitutes is will be highly stimulated by a well-established functional vascularized network. Cobalt (Co) ions are known that can generate a hypoxia-like response and stimulates the production of kinds of angiogenic factors. Herein, we investigated the mechanism of cobalt-doped bioactive borosilicate (36B2O3, 22CaO, 18SiO2, 8MgO, 8K2O, 6Na2O, 2P2O5; mol%) glass scaffolds for bone tissues repairing and blood vessel formation in the critical-sized cranial defect site of rats and their effects on the hBMSCs in vitro were researched. The scaffolds can control release Co2+ ions and convert into hydroxyapatite soaking in simulative body fluids (SBF). The fabircated scaffolds without cytotoxic strongly improves HIF-1α generation, VEGF protein secretion, ALP activity and upregulates the expression of osteoblast and angiogenic relative genes in hBMSCs. Eight weeks after implantation, the bioactive glass scaffolds with 3wt % CoO remarkablely enhance bone regeneration and blood vascularized network at the defective site. In conclusion, as a graft material for bone defects, low-oxygen simulated cobalt-doped bioactive glass scaffold is promising.

Data set for determination of lubrication film thickness and lubrication state between bone and Ti-6Al-4V interface under three biolubrications.

The lubrication states between the friction pairs in lubrications have an important effect on its tribological behavior. Therefore, the aim of this complementary data article is to identify the corresponding lubrication states between bone and Ti-6Al-4V interface in three biolubricants in reciprocation sliding by the Stribeck theory. Among that, three biolubricated film thicknesses at the stroke center and stroke end were separately calculated using the elastohydrodynamic theory. The current data are considered as a complementary for the main work "Tribological behavior of Ti-6Al-4V against cortical bone in different biolubricants" (Wang et al., 2018).

The development of an artificial skin model and its frictional interaction with wound dressings.

Human skin interacts with various materials in our daily life. The interaction between human skin and contacting materials is very important for the development of skin contacting products. Owing to the ethic and different testing results because of the using of in vivo or ex vivo skin, it is important to develop an artificial skin model (ASM) for the study. Therefore, an ASM mimicking the deformation and friction behavior of in vivo human skin was designed based on the evaluation of in vivo human skin behavior, and its frictional interaction with wound dressings was studied. The ASM was prepared by the combination of hydrophilic network carboxyl chitosan (CC) and hydrophobic network polydimethylsiloxane (PDMS). The influence of ingredient ratio, including PDMS/CC and curing agent/PDMS ratio, on the mechanical property of ASM was determined firstly. By adjusting the curing agent/PDMS ratio, the water absorption swelling rate (WASR) of ASM could be controlled to mimic different hydration status of human skin. With the changing of ingredient ratio and hydration level, the elastic modulus and viscoelasticity of ASM can be tailored to be similar to that of in vivo human skin. When the PDMS/CC ratio was 7:3, and PDMS/curing agent ratio was smaller than 1:30, the elastic modulus of ASM was in the range of in vivo inner forearm, and with the increasing of indentation depth, the elastic modulus decreased. Based on the ASM, the frictional interaction between skin/wound dressing/mattress was studied. It was found that although the friction using ASM was slightly higher than that using in vivo inner forearm, but the friction decreasing trend was the same for different kinds of wound dressings. In addition, the friction tested with ASM was less fluctuation, more reliable and reproducible than that tested with in vivo skin, indicating that the ASM was suitable to be used for the studying of frictional interaction between skin and product, such as wound dressings.

Tribological behavior of Ti-6Al-4V against cortical bone in different biolubricants.

Titanium alloys (Ti-6Al-4V) are promising materials as bone implants in clinical surgeries owing to their excellent performances. However, wear debris caused by the tribological behavior of the cortical bone and titanium alloy interface were found to be paramount for implant stability. The contact environment between the cortical bone and Ti-6Al-4V in vivo has been considered to affect the tribological behavior. Currently, the tribological behaviors of bone and Ti-6Al-4V in different biolubricants remain elusive. Therefore, in this work, the tribological behaviors of Ti-6Al-4V plates sliding against bovine cortical bone were investigated in dry sliding and in biolubricants of physiological saline (PS), simulated body fluids (SBF), and fetal bovine serum (FBS). Results show that the friction coefficient and wear rate of the bovine cortical bone and Ti-6Al-4V interface exhibit the same sequence as follows: FBS > SBF > PS > dry sliding. These results are attributed to bone hardness variation and corrosion of different biolubricants. Meanwhile, the effects of normal load and velocity on the tribological behavior of bone and Ti-6Al-4V interface were also investigated in dry sliding and three different biolubricants. Results show that as the normal load is increased and the sliding velocity is decreased, the friction coefficient decreases in dry condition, adhering to the Hertz contact theory. However, according to the boundary lubrication theory, the friction coefficient in three biolubricants correlates positively to the normal load and negatively to the sliding velocity. Moreover, the wear rates of the bone samples increase with the increase in normal load and sliding velocity under dry and biolubrication conditions. Finally, the characterization results indicate that the wear mechanisms of the cortical bone and Ti-6Al-4V interface in dry friction are primarily adhesive and abrasive wear. Further, corrosive wear occurs in biolubrications, apart from adhesive and abrasive wear.

Study on the development of wax emulsion with liquid crystal structure and its moisturizing and frictional interactions with skin.

The moisturizing and frictional interactions between emulsion and skin have a significant influence on the moisturizing efficacy and sensory properties of cosmetics. To deeply understand the interactions, we developed a kind of wax emulsion with liquid crystal structure and studied their interactions with dry, semi-moist and fully-moist skin. The moisturizing interaction was studied by using skin hydration test and tape stripping analysis, and it was found that with the increasing of liquid crystal content in the emulsion, the skin hydration level increased, desquamation index decreased and number of cutaneous lines increased, suggesting the increased moisturizing effect and barrier function. The frictional interaction was studied by finger friction test, and it was found that firstly during and after the application of emulsion on skin, the frictional interaction followed the stribeck-curve rule of lubrication. Secondly, when changing the water content of the substrate skin, the frictional behavior of the whole system showed a bell-curve behavior. Both skin hydration and water amount in the interfacial film played role in the frictional interaction between emulsion and skin, and the frictional interaction mechanism between wax emulsion and finger skin with different type of skin was proposed. This was the first time to study and discuss the effect of skin moist status on the moisturizing and frictional interactions between cosmetic emulsion and skin. The findings were significant for the design of high quality personal care products.

Influence of suture size on the frictional performance of surgical suture evaluated by a penetration friction measurement approach.

The frictional performances of surgical sutures have been found to play a vital role in their functionality. The purpose of this paper is to understand the frictional performance of multifilament surgical sutures interacting with skin substitute, by means of a penetration friction apparatus (PFA). The influence of the size of the surgical suture was investigated. The relationship between the friction force and normal force was considered, in order to evaluate the friction performance of a surgical suture penetrating a skin substitute. The friction force was measured by PFA. The normal force applied to the surgical suture was estimated based on a Hertzian contact model, a finite element model (FEM), and a uniaxial deformation model (UDM). The results indicated that the penetration friction force increased as the size of the multifilament surgical suture increased. In addition, when the normal force was predicted by UDM, it was found that the ratio between the friction force and normal force decreased as the normal force increased. A comparison of the results suggested that the UDM was appropriate in predicting the frictional behavior of surgical suturing.