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Discusses the properties of matter pertaining to whether an object is smooth or rough, defining both words and using examples to illustrate the differences.

The surface that hates almost everything Inspired by the insect-eating Nepenthes pitcher plant, which snares its prey on a surface lubricated by a remarkably slippery aqueous secretion, Joanna Aizenberg and colleagues have synthesized omniphobic surfaces that can self-repair and function at high pressures. Their 'slippery liquid-infused porous surfaces' (or SLIPS) exhibit almost perfect slipperiness towards polar, organic and complex liquids. SLIPS function under extreme conditions, are easily constructed from inexpensive materials and can be endowed with other useful characteristics, such as enhanced optical transparency, through the selection of appropriate substrates and lubricants. Ultra-slippery surfaces of this type might find application in biomedical fluid handling, fuel transport, antifouling, anti-icing, optical imaging and elsewhere. Creating a robust synthetic surface that repels various liquids would have broad technological implications for areas ranging from biomedical devices and fuel transport to architecture but has proved extremely challenging 1 . Inspirations from natural nonwetting structures 2 , 3 , 4 , 5 , 6 , particularly the leaves of the lotus, have led to the development of liquid-repellent microtextured surfaces that rely on the formation of a stable air–liquid interface 7 , 8 , 9 . Despite over a decade of intense research, these surfaces are, however, still plagued with problems that restrict their practical applications: limited oleophobicity with high contact angle hysteresis 9 , failure under pressure 10 , 11 , 12 and upon physical damage 1 , 7 , 11 , inability to self-heal and high production cost 1 , 11 . To address these challenges, here we report a strategy to create self-healing, slippery liquid-infused porous surface(s) (SLIPS) with exceptional liquid- and ice-repellency, pressure stability and enhanced optical transparency. Our approach—inspired by Nepenthes pitcher plants 13 —is conceptually different from the lotus effect, because we use nano/microstructured substrates to lock in place the infused lubricating fluid. We define the requirements for which the lubricant forms a stable, defect-free and inert ‘slippery’ interface. This surface outperforms its natural counterparts 2 , 3 , 4 , 5 , 6 and state-of-the-art synthetic liquid-repellent surfaces 8 , 9 , 14 , 15 , 16 in its capability to repel various simple and complex liquids (water, hydrocarbons, crude oil and blood), maintain low contact angle hysteresis (<2.5°), quickly restore liquid-repellency after physical damage (within 0.1–1 s), resist ice adhesion, and function at high pressures (up to about 680 atm). We show that these properties are insensitive to the precise geometry of the underlying substrate, making our approach applicable to various inexpensive, low-surface-energy structured materials (such as porous Teflon membrane). We envision that these slippery surfaces will be useful in fluid handling and transportation, optical sensing, medicine, and as self-cleaning and anti-fouling materials operating in extreme environments.

A comprehensive comparison of the trends and drivers of global surface and canopy urban heat islands (termed Is and Ic trends, respectively) is critical for better designing urban heat mitigation strategies. However, such a global comparison remains largely absent. Using spatially continuous land surface temperatures and surface air temperatures (2003–2020), here we find that the magnitude of the global mean Is trend (0.19 ± 0.006°C/decade, mean ± SE) for 5,643 cities worldwide is nearly six‐times the corresponding Ic trend (0.03 ± 0.002°C/decade) during the day, while the former (0.06 ± 0.004°C/decade) is double the latter (0.03 ± 0.002°C/decade) at night. Variable importance scores indicate that global daytime Is trend is slightly more controlled by surface property, while background climate plays a more dominant role in regulating global daytime Ic trend. At night, both global Is and Ic trends are mainly controlled by background climate. Plain Language Summary Surface and canopy urban heat islands (surface and canopy UHIs, termed Is and Ic) are two major UHI types. These two counterparts are both related to urban population heat exposure and have long been a focus of urban climate research. However, the differences in the trends and major determinants of Is and Ic over global cities remain largely unclear. Based on spatially continuous land surface temperature and surface air temperature observations from 2003 to 2020, we find that the global mean Is trends are about 6.3 times and 2 times the Ic trends during the day and at night, respectively. During the day, the global Is trend is more regulated by surface property than by background climate, and vice versa for global Ic trend. At night, both the global Is and Ic trends are mainly regulated by background climate. These findings are important for better understanding global urban climate change and informing heat mitigation strategies. Key Points The global Is trend is six‐fold and twofold larger than the Ic trend during the day and at night, respectively During the day, global Is trend is slightly more controlled by surface property, yet background climate plays a dominant role in Ic trend At night, both global Is and Ic trends are more regulated by background climate

Plasmons are directly launched in graphene, and their key parameters — propagation and attenuation — are studied with near-field infrared nano-imaging. Voltage-controlled graphene plasmonics Plasmonic devices, which exploit surface plasmons (electromagnetic waves that propagate along the surface of metals) offer the possibility of controlling and guiding light at subwavelength scales. All eyes are on graphene — atom-thick layers of carbon — as a promising platform for plasmonic applications because it can strongly interact with light and host surface plasmons in the infrared range. Two independent groups reporting in this issue of Nature show that plasmons can be directly launched in graphene, and observed with near-field optical microscopy. Moreover, the wavelengths and amplitudes of the plasmons can be tuned by a gate voltage, a promising capability for the development of on-chip graphene photonics for use in applications including telecommunications and information processing. Surface plasmons are collective oscillations of electrons in metals or semiconductors that enable confinement and control of electromagnetic energy at subwavelength scales 1 , 2 , 3 , 4 , 5 . Rapid progress in plasmonics has largely relied on advances in device nano-fabrication 5 , 6 , 7 , whereas less attention has been paid to the tunable properties of plasmonic media. One such medium—graphene—is amenable to convenient tuning of its electronic and optical properties by varying the applied voltage 8 , 9 , 10 , 11 . Here, using infrared nano-imaging, we show that common graphene/SiO 2 /Si back-gated structures support propagating surface plasmons. The wavelength of graphene plasmons is of the order of 200 nanometres at technologically relevant infrared frequencies, and they can propagate several times this distance. We have succeeded in altering both the amplitude and the wavelength of these plasmons by varying the gate voltage. Using plasmon interferometry, we investigated losses in graphene by exploring real-space profiles of plasmon standing waves formed between the tip of our nano-probe and the edges of the samples. Plasmon dissipation quantified through this analysis is linked to the exotic electrodynamics of graphene 10 . Standard plasmonic figures of merit of our tunable graphene devices surpass those of common metal-based structures.

The human finger is exquisitely sensitive in perceiving different materials, but the question remains as to what length scales are capable of being distinguished in active touch. We combine material science with psychophysics to manufacture and haptically explore a series of topographically patterned surfaces of controlled wavelength, but identical chemistry. Strain-induced surface wrinkling and subsequent templating produced 16 surfaces with wrinkle wavelengths ranging from 300 nm to 90 μm and amplitudes between 7 nm and 4.5 μm. Perceived similarities of these surfaces (and two blanks) were pairwise scaled by participants and interdistances among all stimuli were determined by individual differences scaling (INDSCAL). The tactile space thus generated and its two perceptual dimensions were directly linked to surface physical properties – the finger friction coefficient and the wrinkle wavelength. Finally, the lowest amplitude of the wrinkles so distinguished was approximately 10 nm, demonstrating that human tactile discrimination extends to the nanoscale.

Additive manufacturing using metal powders is becoming increasingly popular due to its versatility in creating structural components of various shapes. Among the various additive manufacturing methods (or 3D printing), direct metal laser sintering (DMLS) is one of the most frequently used technologies. The material most frequently used in DMLS technology is the titanium (Ti6Al4V) alloy, widely preferred in defense, aerospace, automotive, energy, and biomedical industries. This research study examines the mechanical and surface porosity and roughness properties of the 3D-printed Ti6Al4V (Grade 23) alloy specimens. In addition to additive manufacturing, a post-processing treatment known as stress-relieving (SR) heat treatment is also utilized for additively manufactured specimens. Four differently shaped walls (diamond, square, circle, and hexagon) were additively manufactured. The mechanical properties of the 3D-printed Ti6Al4V alloy specimens were tested using compression testing and hardness tests using Rockwell and Vickers scales. These tests were conducted before and after post-process SR heat treatment. Additionally, surface roughness analysis was conducted on the specimens to determine any changes in the material’s surface properties after the SR heat treatment. It was observed that the heat-treated (HT) specimens existed to have more cracks and oxidation compared to the non-heat-treated (NHT) ones. According to the surface roughness results, the circular-shaped heat-treated wall (CSHTW) specimen has the lowest average roughness (Ra) value of 210.31 µin (5.34 µm), and the corresponding maximum height (Rz) was 897.99 µin (22.81 µm). Also, the average Rockwell hardness value of the HT specimens was reported to present an increase of approximately 3% compared to the NHT specimens. The diamond-shaped heat-treated wall (DSHTW) specimen exhibited the highest Vickers hardness value of 605.08 (± 233.98) HV. It was found that the CSHTW specimens had the highest elastic modulus and yield strengths among all the geometries, with a value 38 GPa and 1380 MPa, respectively, indicating that they could resist deformation better than the other specimens. Overall, this study is important because additively manufactured Ti6Al4V alloy components are increasingly used in many industries, as it offers significant reductions in costs, material waste, manufacturing lead times, and improved performance outcomes.

This study evaluated the effects of 30% hydrogen peroxide (HP) solution incorporated with strontium-containing Fluorapatite (Sr-FAp) on whitening efficacy and enamel surface properties, aiming to minimize enamel damage during bleaching. A total of 60 extracted bovine teeth were stained with black tea and divided into five groups ( n  = 12): DW (distilled water), 30% HP, 1 wt% Sr-FAp + HP, 5 wt% Sr-FAp + HP, and 10 wt% Sr-FAp + HP. DW and HP solutions with or without Sr-FAp were applied three times for 20 min each. The surface color alteration, gloss, roughness, microhardness, and enamel microstructure were analyzed before and after bleaching. All experimental groups showed significantly higher ΔE ab values than those of the DW group ( p  < 0.05), with no significant differences between Sr-FAp concentrations ( p  > 0.05). ΔWI D and ΔE₀₀ followed similar trends. Gloss decreased in all HP-treated groups compared to the DW group ( p  < 0.05), with the 10 wt% Sr-FAp group showing the lowest gloss ( p  < 0.05). There were no significant differences in surface roughness ( p  > 0.05), whereas the 10 wt% Sr-FAp group showed the highest microhardness value ( p  < 0.05). Observations of the enamel surface revealed the presence of Sr-FAp nanoparticles in all Sr-FAp groups. HP containing Sr-FAp effectively whitened the teeth while preserving the enamel microhardness and structure via a protective Sr-FAp layer. Sr-FAp shows promise as a remineralizing filler for whitening treatments, maintaining whitening efficacy while minimizing enamel damage.

Synthesis for new pyrazolin derivatives, which oriented for coordination with Cr(III) ion then all new synthesizes were characterized with reliable techniques. Octahedral geometry was the only form suggested from bi-negative tetra-dentate mode of bonding within bi-nuclear complexes. Such offering is based on analytical and spectral tools (IR, UV–Vis and MS). TGA confirms and discriminates water molecules profiles with relative to coordination sphere. Practical and computational XRD patterns appeared having high extent of similarity attributing to nano-crystalline particulate sizes. Hirshfeld surface properties and the efficiency of molecular-contact in crystal-packing, were obtained upon Crystal explorer 3.1 software beside VESTA package. Some physical indices were estimated based on frontier energy gaps over optimized structures upon Gauss-view software. Computational simulation approach was implemented to monitor changes on cancer cell proteins after treatment by new Cr(III) complexes, for assessment. Promising antitumor activity might be expected for Cr(III)-L 4 , Cr(III)-L 3 and Cr(III)-L 2 complexes, based on exported interaction parameters. It is worthy to note that, in-vitro assay reflects an excellent cytotoxicity recorded for such three complexes, in excellent harmony with simulation suggestions.

While the reciprocity between bioceramics and living cells is complex, it is principally governed by the implant’s surface chemistry. Consequently, a deeper understanding of the chemical interactions of bioceramics with living tissue could ultimately lead to new therapeutic strategies. However, the physical and chemical principles that govern these interactions remain unclear. The intricacies of this biological synergy are explored within this paper by examining the peculiar surface chemistry of a relatively new bioceramic, silicon nitride (Si 3 N 4 ). Building upon prior research, this paper aims at obtaining new insights into the biological interactions between Si 3 N 4 and living cells, as a consequence of the off-stoichiometric chemical nature of its surface at the nanometer scale. We show here yet unveiled details of surface chemistry and, based on these new data, formulate a model on how, ultimately, Si 3 N 4 influences cellular signal transduction functions and differentiation mechanisms. In other words, we interpret its reciprocity with living cells in chemical terms. These new findings suggest that Si 3 N 4 might provide unique new medicinal therapies and effective remedies for various bone or joint maladies and diseases.

Peri-implantitis is an unsolved but critical problem with dental implants. It is postulated that creating a seal of gingival soft tissue around the implant neck is key to preventing peri-implantitis. The objective of this study was to determine the effect of UV surface treatment of titanium disks on the adhesion strength and retention time of oral connective tissues as well as on the adherence of mucosal fibroblasts. Titanium disks with a smooth machined surface were prepared and treated with UV light for 15 min. Keratinized mucosal tissue sections (3 × 3 mm) from rat palates were incubated for 24 h on the titanium disks. The adhered tissue sections were then mechanically detached by agitating the culture dishes. The tissue sections remained adherent for significantly longer (15.5 h) on the UV-treated disks than on the untreated control disks (7.5 h). A total of 94% of the tissue sections were adherent for 5 h or longer on the UV-treated disks, whereas only 50% of the sections remained on the control disks for 5 h. The adhesion strength of the tissue sections to the titanium disks, as measured by tensile testing, was six times greater after UV treatment. In the culture studies, mucosal fibroblasts extracted from rat palates were attached to titanium disks by incubating for 24, 48, or 96 h. The number of attached cells was consistently 15–30% greater on the UV-treated disks than on the control disks. The cells were then subjected to mechanical or chemical (trypsinization) detachment. After mechanical detachment, the residual cell rates on the UV-treated surfaces after 24 and 48 h of incubation were 35% and 25% higher, respectively, than those on the control surfaces. The remaining rate after chemical detachment was 74% on the control surface and 88% on the UV-treated surface for the cells cultured for 48 h. These trends were also confirmed in mouse embryonic fibroblasts, with an intense expression of vinculin, a focal adhesion protein, on the UV-treated disks even after detachment. The UV-treated titanium was superhydrophilic, whereas the control titanium was hydrophobic. X-ray photoelectron spectroscopy (XPS) chemical analysis revealed that the amount of carbon at the surface was significantly reduced after UV treatment, while the amount of TiOH molecules was increased. These ex vivo and in vitro results indicate that the UV treatment of titanium increases the adhesion and retention of oral mucosa connective tissue as a result of increased resistance of constituent fibroblasts against exogenous detachment, both mechanically and chemically, as well as UV-induced physicochemical changes of the titanium surface.