Native Oxide Layer Research Articles

Liquid metal motor.

SummaryLiquid metal has demonstrated an enormous potential for developing soft functional devices and machines. However, current liquid metal enabled machines suffer from several issues, such as the requirement of a liquid environment, generation of weak actuating forces, and insufficient maneuverability. To overcome these restrictions, here, a motor is developed based on the electrical actuation of liquid metal droplets without the need for conventional electromagnets. The approach is distinguished by (1) the encapsulation of electrolyte and multiple liquid metal droplets within an enclosed system, and (2) the creation of stable and continuous torque outside a liquid environment. In addition, a liquid metal electrical brush is introduced to operate the motor with low friction and low wear. The unique driving mechanism endows the motor with several advantages, including low friction, no sparking, low noise, versatile working environment, and being built from soft materials that could offer new opportunities for developing soft robotics.

Neutron Reflectivity on the Mobile Surface and Immobile Interfacial Layers in the Poly(vinyl acetate) Adsorption Layer on a Si Substrate with Deuterated Toluene Vapor-Induced Swelling.

We investigated the polymer chain dynamics in a 2-3 nm thick poly(vinyl acetate) (PVAc) adsorption layer on a Si substrate with a native oxide layer via neutron reflectometry combined with toluene vapor-induced swelling. We can investigate the polymer chain dynamics difference in the film thickness direction by the difference in the degree of swelling of the polymer layers detected by neutron reflectometry. The mobility of the polymer chains depends on the distance from the substrate. The results elucidated that the interfacial layer with a thickness of approximately 1 nm did not swell at all with toluene vapor, which is a solvent for PVAc. Meanwhile, the surface layer excessively swells with toluene vapor compared to the bulk. This indicates that the polymer chain within the interfacial region is immobilized by the substrate through hydrogen-bonding interaction, but in the surface region, the surface effect overcomes this interfacial interaction. We concluded that the polymer chains in the adsorption layer are either strongly constrained to the substrate, owing to hydrogen bonding, or more mobile than the bulk, owing to the surface effect.

Sulfide Passivation of InP(100) Surface

Passivation of the n-InP(100) surface with sodium sulfide (Na2S) aqueous solution is analyzed by photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). The room-temperature PL intensity increases essentially even after short treatment with sulfide solution for 1 min. The enhancement in the room-temperature PL intensity after passivation decreases with the increase in the bulk doping level of the semiconductor. Time-resolved PL studies performed at liquid-nitrogen temperature indicate reduction in the surface recombination velocity. This improvement of the PL intensity occurs just after transformation of the native oxide layer consisting mainly of indium phosphates to the passivating layer consisting of indium sulfides and oxides. The surface bands in n-InP(100) remained nearly flat both before and after sulfide passivation.

Metallophobic Coatings to Enable Shape Reconfigurable Liquid Metal Inside 3D Printed Plastics.

Liquid metals adhere to most surfaces despite their high surface tension due to the presence of a native gallium oxide layer. The ability to change the shape of functional fluids within a three-dimensional (3D) printed part with respect to time is a type of four-dimensional printing, yet surface adhesion limits the ability to pump liquid metals in and out of cavities and channels without leaving residue. Rough surfaces prevent adhesion, but most methods to roughen surfaces are difficult or impossible to apply on the interior of parts. Here, we show that silica particles suspended in an appropriate solvent can be injected inside cavities to coat the walls. This technique creates a transparent, nanoscopically rough (10-100 nm scale) coating that prevents adhesion of liquid metals on various 3D printed plastics and commercial polymers. Liquid metals roll and even bounce off treated surfaces (the latter occurs even when dropped from heights as high as 70 cm). Moreover, the coating can be removed locally by laser ablation to create selective wetting regions for metal patterning on the exterior of plastics. To demonstrate the utility of the coating, liquid metals were dynamically actuated inside a 3D printed channel or chamber without pinning the oxide, thereby demonstrating electrical circuits that can be reconfigured repeatably.

Influence of Additive Inclusion on Hardness of Electroplated Al Film with Nanometer-Level Flatness from Chloroaluminate Ionic Liquid

In this study, we report the influence of additive inclusion on the hardness of an Al film electrochemically deposited from the chloroaluminate ionic liquid. The additive inclusion drastically increased the hardness as well as the surface flatness. The measured elastic modulus and mechanical hardness of Al on Au seed layer were 71.9 GPa and 10.3 GPa, respectively. Introduction Electrochemical deposition (ECD) process is widely used for micro-electro mechanical system (MEMS) fabrication and packaging to form a relatively thick metallization. The process is often selected owing to its low-cost, high deposition rate and availability to tune various properties of the resulting deposit. Its application spans from the structural material of sensors [1] to wafer-level bonding [2].The emergence of ionic liquid as a solvent has allowed ECD of various materials which are impossible to reduce in water, including Al. Additive inclusion has been introduced to reduce the surface roughness of the resulting deposit [4]. On the other hand, material properties are also of importance for designing MEMS based on the film. However, the influence of additive inclusion on the material property has not been investigated yet. Therefore, this study aims to close the gap. Experimental method The ECD process was performed on a Si substrate with Au or Pt seed layer using a commercially available AlCl3–1-ethyl-3-methylimidazolium chloride ([EMIm]Cl) (3:2) ionic liquid electrolyte. A 0.5 g/L 2-chloronicotinyl chloride was introduced as the additive to improve the surface roughness. The deposition was carried out using direct current (DC) at 10 mA/cm2 current density under room temperature for 60 min, which resulted in around 7 μm thickness of deposits. To avoid the degradation of the ionic liquid solvent, the deposition was performed inside a glove box with continuous flow of an inert and dry N2 gas. Results and discussions Scanning electron micrographs (SEMs) of the deposited films are shown in Fig. 1 (a), (b) and (c). The difference of surface roughness between films deposited in electrolyte without and with the additive inclusion is quite significant. Fig. 1 (d) shows the quantitative comparison. The surface roughness was reduced to a few nm, which is 2 orders magnitude less than that of without additive. The additive inclusion also introduces a 15% reduction of the deposition rate.The influence of the additive inclusion in the electrolyte to the mechanical properties of the resulting film is shown in Fig. 1 (e). The hardness and elastic modulus of the deposited films were characterized by nanoindentation using a diamond tetrahedron indenter, i.e. Berkovich tip. The indentation depth was maintained to be more than 100 nm and less than 10% of the film thickness to avoid the influence of the native oxide layer and the substrate.The evaluation results are compared to previously reported values of bulk Al and thin films deposited using other techniques [5,6]. Compared to the bulk, thin films have a higher nanoindentation hardness. This might be partly attributed to the grain size refining, which is in agreement with the Hall-Petch relation. The nanoindentation hardness became further higher for films deposited with additive inclusion. This significant strengthening can also be partly attributed to the grain size refining [4].The elastic modulus of the electrodeposited Al film on the Au seed layer without additive inclusion and the film deposited on the Pt seed layer with additive inclusion were significantly lower compared to other conditions. The significantly low elastic modulus regardless of high hardness can be caused by the existence of pores as well as other defects in the grain boundaries, including vacancies, dislocations, impurities and the local distribution of strain [7]. The difference in the deposition mechanism between the Au and Pt seed layers is to be investigated in the future. Conclusion In this study, the evolution of mechanical properties of the electrodeposited Al films with the inclusion of additive has been investigated. Enhancement of nanoindentation hardness was observed, mainly due to the grain boundary hardening. This result is useful as a design guide for future MEMS application of the film. References S. Alper et al., Sens. Act. A Phys. 132 (1), pp. 171–181 (2006).M. S. Al Farisi et al., J. Micromech. Microeng. 27 (1), p. 015029 (2017).F. Endres ChemPhysChem 3 (2), pp. 144–154 (2002).P. Sheng et al., Mater. Corr. 66 (11), pp. 1338–1443 (2015).Y. Y. Lim et al., J. Mat er . Res. 14 (6), pp. 2314–2327 (1999).M.F. Doerner et al., J. Mat er . Res. 1 (6), pp. 845–851 (1986).Y. Nakoshi et al., Jpn. J. Appl. Phys. 58, p. SBBC04 (2019). Figure 1

Cathodic Corrosion Protection of Steel with Electroplated Aluminum Alloys

Aluminum has excellent corrosion properties due to the formation of a dense oxide layer. This layer spontaneously forms in contact with air and protects the bulk material from further oxidation. Unfortunately, the formation of the natural oxide layer renders pure aluminum passive so that it is not a good candidate for the corrosion protection of a more noble substrate like steel. Therefore, for applications as a corrosion protection layer aluminum should be alloyed with other elements to prevent complete passivation.Electrodeposition is an elegant and cost-efficient method to apply thin coatings on various substrates with complex geometries. The layer properties can be easily controlled by adjusting the deposition parameters (current density, temperature, electrolyte composition). Aluminum cannot be deposited from aqueous electrolytes because of its negative Nernst potential (-1.66 V vs. NHE). Ionic liquids (ILs) are suitable electrolytes for the deposition of reactive metals, such as Al, Nb and Ta. They have a broad electrochemical window (> 3 V) and high electrical conductivity, and show good solubility for many metal salts.This paper will discuss the deposition of binary aluminum alloys from imidazolium-based ILs and their corrosion behaviour. Results from potentiodynamic polarization experiments will be compared with results from salt spray tests and long-term environmental exposure experiments (> 1 year) to assess the suitability of the alloys for cathodic corrosion protection of steel.

UV fluorescence enhancement by aluminum and magnesium equilateral bowtie nanoantennas

The intrinsic fluorescence of biomolecules such as proteins and nucleic acids lies in the ultraviolet (UV) range of the spectrum. UV plasmonic nano-structures have been shown to enhance the fluorescence quantum yield and reduce the lifetimes of various biomolecules. Fluorescence enhancement is contributed to by both excitation rate and emission rate enhancement. Since biomolecules are prone to photon-degradation in the UV range, excitation rate enhancement should be minimized, while radiative rate enhancement should be maximized. Although numerous nano-structures have been proposed both numerically and experimentally to enhance the fluorescence of native biomolecules, very few studies have achieved more than 10x radiative rate enhancement. Here we report systematic studies of fluorescence enhancement by equilateral bowtie nano-antennas (BNA) made of aluminum (Al) or magnesium (Mg) in the ultraviolet region. We modeled the emission rate enhancement using the excitation and emission peak wavelength of tryptophan. The quantum yield of tryptophan is also taken into account. Our results show that with the optimal geometry, Al BNA with oxide yields an excitation enhancement of 21× at the excitation wavelength of tryptophan (270nm), a radiative enhancement of 37×, a quantum yield enhancement of 5×, and a net fluorescence count rate enhancement of 64× at the emission wavelength of tryptophan (340nm). Mg BNA with oxide sustains the highest Purcell factor enhancement, 14×. The effect of the native oxide layer on both metals is investigated. The studies reported here are meaningful in the design of better UV plasmonic nano-structures for label-free sensing of biomolecules.

Enhanced ductility by Mg addition in the CNT/Al-Cu composites via flake powder metallurgy

The inevitable native oxide layer is a critical issue to achieve high mechanical performance of CNT/Al-alloy composites, especially prepared by powder metallurgy. Here, an easy strategy was proposed to avoid and eliminate the negative effect of native oxide (Al2O3) layer by Mg addition, and significant improvement of ductility was achieved in the CNT/Al-Cu composite. Native Al2O3 remained as continuous layers around CNTs or clusters of fragments in the CNT/Al-Cu without Mg addition. Mg addition transformed the native Al2O3 layer into spinel MgAl2O4 nano-phases dispersed both inside grains and on the interfaces. It is supposed that this transformation of oxide layer could improve the interfacial bonding due to Al-Al and Al-CNT direct interfacial contact. As a result, compared with CNT/Al-Cu composites, the tensile strength only changed a little, however, almost two times of fracture ductility was achieved by Mg addition in the final composites.

Design and Fabrication of Silicon Nanowire-Based Biosensors with Integration of Critical Factors: Toward Ultrasensitive Specific Detection of Biomolecules.

As critical factors affecting the sensing performance of silicon nanowire (SiNW) biosensors, the structure, functional interface, and detection target were analyzed and designed to improve sensing performance. For an improved understanding of the dependence of sensor structure on sensitivity, a simple theoretical analysis was proposed to predict the sensitivity of biosensors with different SiNW types, widths, and doping concentrations. Based on the theoretical analysis, a biosensor integrating optimized critical factors was designed and fabricated. Optimizations focusing on the following aspects are considered: (1) employing n-type SiNW and controlling the impurity doping concentration of SiNW at approximately 2 × 1016-6 × 1016 atoms/cm3 to obtain a suitable charge density, (2) minimizing the SiNW width to 16.0 nm to increase the surface area-to-volume ratio, (3) using a native oxide layer on SiNW as a gate insulator to transport the captured charge molecules closer to the SiNW surface, (4) modifying the SiNW surface by 2-aminoethylphosphonic acid coupling to form a high-density self-assembled monolayer for enhancing the stability bound molecules, and (5) functionalizing the SiNW with ovalbumin molecules for specifically capturing the target immunoglobulin G (IgG) molecules. The sensing performance was evaluated by detecting IgG with concentrations ranging from 6 aM to 600 nM and control experiments. The SiNW biosensor revealed ultrahigh sensitivity and specific detection of target IgG with a measured limit of detection of 6 aM. The integration of the critical SiNW biosensor factors provides a significant possibility of a rapid and ultrasensitive diagnosis of diseases at their early stages.

Effect of native oxide on the crystal orientation contrast in SEM micrographs obtained at hundreds, tens and units of eV

This paper aims to elucidate the effect of native air-formed oxide on the crystallographic contrast between differently oriented copper grains in scanning electron microscope images obtained at energies from 0 eV up to 1 keV. The contrast between the Cu grains is strongly affected by the presence of native oxide. The crystallographic orientation contrast between the grains without covering the native oxide layer is relatively weak at hundreds of eV, negligible at tens of eV, and dramatically increases at energies below 10 eV. At extremely low landing energies, say below ~ 1 eV, the surface potential differences caused by work function variations between the differently oriented Cu grains affect the primary electrons, which enables us to obtain the micrographs with high crystallographic contrast. This contrast becomes surprisingly visible even if the grains are covered by a several nm thick native oxide layer. The presence of the native air-formed oxide layer on the Cu surface is inconsiderable for the contrast formation at energies close to the mirror conditions (< 1 eV). The surface potential differences originating in the substrate can affect the incident electrons through the native oxide film situated on the Cu surface. Scanning low-energy electron microscopy is a powerful tool for mapping local work function differences with a spatial resolution slightly better than 30 nm due to high sensitivity to local electrical potentials.

Positronium formation at 4H SiC(0001) surfaces

Positronium formation at 4H SiC(0001) surfaces were investigated upon the removal of natural oxide layers by hydrofluoric acid etching and heat treatment at 1000 K in ultra-high vacuum. Two types of positronium were observed in the positronium time-of-flight (PsTOF) measurements irrespective of conduction type and surface polarity. One type formed the major part of the PsTOF spectrum with a maximum energy of 4.7 ± 0.3 eV. This energy exceeded the theoretical value calculated with valence electrons. The PsTOF spectrum shape was different from those of metal surfaces, suggesting that the surface state electrons or conduction electrons need to be considered as the positronium source. Another positronium appeared at 1000 K in the tail of the PsTOF spectrum with a maximum energy of 0.2–0.5 eV. This thermally-assisted athermal positronium may be formed via the surface state positrons and electrons.

Influence of the transient conditions on release of corrosion products and oxidation of alloy 690 tubes during pressurized water reactor restart after steam generators replacement

The radioactivity of the Reactor Coolant System (RCS) of Pressurized Water Reactors (PWRs) mainly comes from the release of corrosion products of Steam Generator (SG) tubes made of Ni-base alloys. In order to reduce this activity and thus the radiation exposure of PWR operators during maintenance operations, it is necessary to minimize the release. That requires prior understanding of the various mechanisms involved. EDF R&D constructed a loop, BOREAL, to specifically measure rates of release of SG tubes in various conditions of primary environment. Tubes were usually tested at high temperature, under constant conditions of primary chemistry. So, it is necessary to carefully investigate the impact of transient conditions during a PWR restart after SG replacement. Tests were performed on the industrial material with curvature, roughness, defects and heterogeneities, regularly observed on this type of component. Characterisations of the inner surface were done on as-received and corroded specimens of SG tubes and were correlated with the obtained release kinetics.The native oxide layer is formed of a very thin layer (1-2 nm) of oxidised matrix, without specific enrichment. During the restart, the most critical step for the release phenomenon is revealed from 170°C to 297°C. The majority of the metal is indeed released into the fluid during this step. The characterisations after release tests have made it possible to propose oxidation and release mechanism during a PWR restart after SG replacement. Up to 170°C, a thin layer of amorphous chromium oxide is formed by selective dissolution of iron and nickel. When the temperature rises, this chromium oxide layer is not stable enough to be protective and the diffusion phenomena are activated. At 325°C, the oxide does not exhibit any particular enrichment and corresponds to an oxidised metal layer; an equilibrium is established and the rate of release reaches a pseudo-stationary regime.

3D-graphene-laser patterned p-type silicon Schottky diode

The influence of the laser patterning (LP) process on the quality of graphene (Gr) film and Schottky diode characteristics was researched in this study. First of all, p-type silicon (Si) was patterned by homemade femtosecond laser source. To compare the resulting effect, non-patterned n-Si and p-Si were used as substrates. To achieve vertically oriented three-dimensional (3D) Gr nanosheets (VGNs) onto the laser patterned p-type Si, non-patterned n-Si, and p-Si substrates, we used Radio-Frequency Plasma Enhanced Chemical Vapor Deposition (RF-PECVD) technique. Then, Raman analyses for VGNs obtained on patterned and non-patterned p-Si and n-Si substrates were conducted. All results indicate that the Gr obtained on all substrates is vertically oriented. Scanning electron microscopy (SEM) analyses were also performed to obtain information about the morphological properties of the 3D Gr structure. In addition, the influence of the laser patterning at the Gr-Si interface was evaluated by comparing two sets of devices which are junctions of Gr-Laser Patterned Si (Gr-LPSi) and Gr-Insulator-Silicon (Gr-I-Si) at 300 K in the dark medium. D1 device consists of a Gr-LPSi junction that involves RF-PECVD grown Gr on the silicon, whose surface exposed the laser beam for patterning. D2 device consists of a Gr-I-Si junction that involves RF-PECVD grown Gr onto the silicon, whose surface involves a thin native oxide layer (~2 nm). The results show that the laser treatment causes an increment in Schottky barrier height (SBH) and decreases leakage currents under a reverse bias voltage of the diode. Notably, we have seen the influence of the laser patterning process on 3D Gr nano-sheets which is that the entire surface of the substrate has now reformed new structures in the nano-sphere and nano-rose morphology, so we believe that this is the first work that shows these structures in this form.

Modeling the Interface between Lithium Metal and Its Native Oxide.

Owing to their high theoretical capacities, batteries that employ lithium (Li) metal as the negative electrode are attractive technologies for next-generation energy storage. However, the successful implementation of lithium metal batteries is limited by several factors, many of which can be traced to an incomplete understanding of surface phenomena involving the Li anode. Here, first-principles calculations are used to characterize the native oxide layer on Li, including several properties associated with the Li/lithium oxide (Li2O) interface. Multiple interface models are examined; the models account for differing interface (chemical) terminations and degrees of atomic ordering (i.e., crystalline vs amorphous). The interfacial energy, formation energy, and strain energies are predicted for these models. The amorphous interface yields the lowest interfacial formation energy, suggesting that it is the most probable model under equilibrium conditions. The work of adhesion is evaluated for the crystalline interfaces, and it is found that the O-terminated interface exhibits a work of adhesion more than 30 times larger than that of the Li-terminated model, implying that Li will strongly wet an oxygen-rich Li2O surface. The electronic structure of the interfaces is characterized using Voronoi charge analysis and shifts in the Li 1s binding energies. The width of the Li/Li2O interface, as determined by deviations from bulklike charges and binding energies, extends beyond the region exhibiting interfacial structural distortions. Finally, the transport of Li ions through the amorphous oxide is quantified using ab initio molecular dynamics. Facile transport of Li+ through the native oxide is observed. Thus, increasing the percentage of amorphous Li2O in the solid electrolyte interphase may be beneficial for battery performance. In total, the phenomena quantified here will aid in the optimization of batteries that employ high-capacity Li metal anodes.

Particle-based simulation of cold spray: Influence of oxide layer on impact process

High-speed cold spraying of micro-particles, at temperatures well below their melting point, impinging on desired substrates is a useful emerging additive process. One principal element believed to dramatically influence the bonding strength and final coating quality of many metallic cold-spray deposits is the native oxide layer on the surface of the impinging particles and substrate. Here, smoothed-particle hydrodynamics (SPH), a mesh-free, particle-based method, is used to simulate cold-spraying, including the action of oxide layers in the deposition and bonding processes. The effect of increasing particle impact velocity on oxide breakup and subsequent bonding is studied. Particle/substrate bonding is quantified via metallic interaction at the interface and found to continuously improve with increasing velocity well beyond the critical velocity. The coefficient of restitution is also calculated for different oxide layer thicknesses on the particle and the substrate. The effects of particle diameter and oxygen content on the impact process are reported and compared to results from the literature. The particle-based simulation approach is found to reproduce experimentally characterized trends in oxide content effect and provide insight into the mechanisms of oxide breakup during bonding.

Effect of Surface Treatment on the Charge Density at the Interface between GdHgTe Epitaxial Films and Al$${}_{\mathbf{2}}$$O$${}_{\mathbf{3}}$$ Grown by Atomic Layer Deposition

The effect of the different surface treatment of Hg $${}_{1-x}$$ Cd $${}_{x}$$ Te (CMT) films before the atomic layer deposition of Al $${}_{2}$$ O $${}_{3}$$ dielectric on the charge at the dielectric–semiconductor interface has been studied. Metal–dielectric–semiconductor (MDS) structures with different surface treatment before the deposition of a dielectric have been manufactured. The capacitance–voltage characteristics of CMT based MDS structures have been measured alongside with the surface charge density. The surface charge is non-uniformly distributed over the surface of films with $$x=0.22$$ and a natural oxide layer and equal to $$(0.8{-}1.8)\times 10^{-8}$$ C/cm $${}^{2}$$ , and this may lead to the inversion of the surface conductivity type. The exposure of these CMT structures in mercury vapor at room temperature leads to the formation of a negative charge within a range of $$-(0.4{-}1.6)\times 10^{-8}$$ C/cm $${}^{2}$$ .

Effect of Native Oxide Layer on the Water Contact Angle to Determine the Surface Polarity of SiC Single Crystals

Effect of Native Oxide Layer on the Water Contact Angle to Determine the Surface Polarity of SiC Single Crystals

Thin TiO2 Coatings by ALD Enhance the Cell Growth on TiO2 Nanotubular and Flat Substrates.

The present work exploits Ti sheets and TiO2 nanotube (TNT) layers and their surface modifications for the proliferation of different cells. Ti sheets with a native oxide layer, Ti sheets with a crystalline thermal oxide layer, and two kinds of TNT layers (prepared via electrochemical anodization) with a defined inner diameter of 12 and 15 nm were used as substrates. A part of the Ti sheets and the TNT layers was additionally coated by thin TiO2 coatings using atomic layer deposition (ALD). An increase in cell growth of WI-38 fibroblasts (>50%), MG-63 osteoblasts (>30%), and SH-SY5Y neuroblasts (>30%) was observed for all materials coated by five cycles ALD compared to their uncoated counterparts. The additional ALD TiO2 coatings changed the surface composition of all materials but preserved their original structure and protected them from unwanted crystallization and shape changes. The presented approach of mild surface modification by ALD has a significant effect on the materials' biocompatibility and is promising toward application in implant materials.

Approaches for deep-ultraviolet surface plasmon resonance sensors.

Aluminum (Al) is a preferred metal for designing deep-ultraviolet (DUV) surface plasmon resonance (SPR)-based sensors. The native oxide layer (alumina), which grows when the Al film is exposed to air, adds an extra layer to the multilayer stack and consequently affects the DUV-SPR sensing performance. To mitigate the performance loss in DUV-SPR-based sensing, new, to the best of our knowledge, approaches are considered here. We first consider chromium, indium (In), nickel, and platinum as alternative plasmonic materials to Al. In-film-based DUV-SPR sensors exhibit the best performance parameters compared to these alternative materials. We next consider the approach of replacing the native oxide layer by an ultrathin gold (Au) layer on top of bare Al or In. With an optimal Au thickness, higher sensitivity as compared to oxidized metals is observed. The next approach adds one or more graphene layers on top of the bare metal film. In this case, the performance depends on the number of graphene layers, but improvement in sensor characteristics in the DUV is also obtained. The use of Au or graphene overlayers increases the refractive index sensing dynamic range, which can be significant for In with these overlayers under certain operating conditions.

Chemical Mechanical Surface Nano-Structuring (CMNS) Implementation on Titanium Based Implants to Enhance Corrosion Resistance and Control Biocompatibility

Titanium is the metal of choice for many implantable devices including dental prostheses, orthopaedic devices and cardiac pacemakers. Titanium and its alloys are favoured for hard tissue replacement because of their high strength to density ratio providing excellent mechanical properties and biocompatible surface characteristics promoting in-vivo passivation due to spontaneous formation of a native protective oxide layer in the presence of an oxidizer. This study focuses on the development of a three-dimensional chemical, mechanical, surface nano-structuring (CMNS) process to induce smoothness or controlled nano-roughness on the bio-implant surfaces, particularly for applications in dental implants. CMNS is an extension of the chemical mechanical polishing (CMP) process. CMP is utilized in microelectronics manufacturing for planarizing the wafer surfaces to enable photolithography and multilayer metallization. In biomaterials applications, the same approach can be utilized to induce controlled surface nanostructure on three-dimensional implantable objects to promote or demote cell attachment. As a synergistic method of nano-structuring on the implant surfaces, CMNS also makes the titanium surface more adaptable for the bio-compatible coatings as well as the cell and tissue growth as demonstrated by the electrochemical and surface wettability evaluations on implants prepared by DI-water machining versus oil based machining.