Bactericidal Titanium Oxide Nanopillars for Intersomatic Spine Screws

Stiction is a serious problem in microelectromechanical systems (MEMS) due to their large surface area-to-volume ratio. Stiction is closely related to surface forces, which greatly depend on the materials used, surface topography and surface treatment process. In this paper, we investigate surface energies and stiction of commonly used MEMS materials by contact angle measurements and atomic force microscopy (AFM). Dispersive and polar components of surface energies are calculated by Owens–Wendt–Rabel–Kaelble method. Silicon and silicon-related materials have higher polar surface energies than SU-8 and poly-methylmethacrylate (PMMA), thereby have larger surface energies and enhanced tendency for stiction. The nano-scale adhesion forces between Si3N4 tip and surfaces obtained by AFM further verified that silicon wafer with native oxide has 3–4 times higher adhesion force than SU-8 and PMMA. It has been shown that the materials with higher surface energy have higher sticton/adhesion forces. The topography of surface influences the contact angle and stiction, and is also discussed in the paper.

With the aim of checking the validity of methods for characterizing the adhesion between inorganic materials with high surface energies, the properties of the adhesion between an inorganic material (indium tin oxide (ITO)) and model surfaces with various surface energies (Cl-, NH2-, CH(3)-, and CF3-functionalized surfaces) were evaluated using atomic force microscopy (AFM) and the Johnson-Kendall-Roberts (JKR) apparatus. For this purpose, the AFM tip and the JKR lens were modified with ITO using radio frequency (rf) magnetron sputtering. The work of adhesion between the ITO coating and each model surface was estimated using AFM and the JKR apparatus and compared with the result obtained from contact angle measurements. The adhesion forces determined from the force-displacement curves (AFM) were found to agree with the predictions of the Derjaguin-Muller-Toporov (DMT) theory. The JKR equation used in the interpretation of the JKR experiments was modified by taking into account the differences between the surface and bulk moduli of the ITO-coated poly(dimethylsiloxane) (PDMS) lens. The ratio of the surface modulus to the bulk modulus we used in this modified JKR equation was obtained by determining the slope of the attracting part of the force-displacement curve. The values of the work of adhesion calculated using the modified JKR equation were also found to agree with the values obtained from contact angle measurements. We conclude that the two methods using AFM and the JKR apparatus can be used in the evaluation of the work of adhesion between inorganic materials with high surface energies such as metal and metal oxide surfaces.

To determine the effects of surface modification on implant osseointegration in vivo, we first immobilized polydopamine onto 70-nm diameter TiO2 nanotubes as an intermediate layer, and then conjugated a 21 amino acid peptide sequence (the so-called "knuckle peptide") of bone morphogenetic protein-2 (BMP-2) onto the nanotubes created by electrochemical anodization. We inserted these implants into the tibiae of rabbits and measured the gene expression and bone formation around them. The successful fabrication of BMP-2 knuckle peptide was confirmed by contact angle measurement, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The histological features and the amount of bone fluorescence around the implants on non-decalcified sections were investigated at 3, 5, 8, and 12 weeks after implantation using traditional light and fluorescence microscopy, and the gene expression of alkaline phosphatase, osterix, collagen-I, and tartrate-resistant acid phosphatase was examined by real-time PCR at 1, 2, 3, 4, and 5 weeks after implantation. The results demonstrated a significant increase in bone-implant contact, quantity of fluorescence, and gene expression levels of the bone attached to implants with immobilized BMP-2 knuckle peptide compared with the other two control groups. In conclusion, the surface functionalization of TiO2 nanotubes with BMP-2 knuckle peptide was beneficial for osseointegration and this approach could be further developed to improve Ti-based implants for various applications.

The influence of substrate absorbency on coating surface energy

Monolayers of 3-(12-mercaptododecyl)phenol and 4-(12-mercaptododecyl)phenol are prepared to investigate the relationship between the interfacial molecular structure and the surface energy of modified interfaces. These modified interfaces are characterized by reflection absorption infrared spectroscopy, reductive desorption, and contact angle measurements. Contact angle measurements with water (γ = 72.0 mN/m), glycerol (γ = 63.2 mN/m), and ethylene glycol (γ = 48.1 mN/m) show that monolayers of 4-(12-mercaptododecyl)phenol have a higher surface energy (∼42 mN/m) than 3-(12-mercaptododecyl)phenol monolayers (∼31 mN/m). Furthermore, Fowkes analysis of the contact angle data show that only ∼8% of the surface energy of the 4-(12-mercaptododecyl)phenol monolayer arises from dispersive interactions, while ∼30% of the total surface energy of 3-(12-mercaptododecyl)phenol monolayers comes from dispersive interactions. These surface energy results along with the spectral data suggest that the hydroxyl group with monolayers of 4-(12-mercaptododecyl)phenol is oriented away from the substrate and into the adjacent phase more than is found with monolayers of 3-(12-mercaptododecyl)phenol.

The surface characterisation and comparison of two potential sub-micron, sugar bulking excipients for use in low-dose, suspension formulations in metered dose inhalers

Investigation of surface energy for organic light emitting polymers and indium tin oxide

Because many physical and chemical processes occur at surfaces, surface atomic structure is a critical factor affecting the properties of materials. Due to the presence of high-density atomic steps and edges and abundant unsaturated coordination sites, micro- and nanocrystallites with high-energy surfaces usually exhibit greater reactivity than those with low-energy surfaces. However, high-energy crystal surfaces are usually lost during crystal growth as the total surface energy is minimized. Therefore, the selective exposure of high-energy facets at the surface of micro- and nanocrystallites is an important and challenging research topic. Metal oxides play important roles in surface-associated applications, including catalysis, gas sensing, luminescence, and antibiosis. The synthesis of metal oxide micro- and nanocrystallites with specific surfaces, particularly those with high surface energies, is more challenging than the synthesis of metal crystals due to the presence of strong metal-oxygen bonds and diverse crystal structures. In this Account, we briefly summarize recent progress in the surface-structure-controlled synthesis of several typical metal oxide micro- and nanocrystallites, including wurtzite ZnO, anatase TiO2, rutile SnO2, and rocksalt-type metal oxides. We also discuss the improvement of surface properties, focusing on high-energy surfaces. Because of the huge quantity and diverse structure of metal oxides, this Account is not intended to be comprehensive. Instead, we discuss salient features of metal oxide micro- and nanocrystallites using examples primarily from our group. We first discuss general strategies for tuning the surface structure of metal oxide micro- and nanocrystallites, presenting several typical examples. For each example, we describe the basic crystallographic characteristics as well as the thermodynamic (i.e., tuning surface energy) or kinetic (i.e., tuning reaction rates) strategies we have used to synthesize micro- and nanocrystallites with high surface energies. We discuss the structural features of the specific facets and analyze the basis for the enhanced performance of the metal oxide micro- and nanocrystallites in water splitting, the degradation of organic pollutants, gas sensing, catalysis, luminescence, and antibiosis. Finally, we note the future trends in high-energy-facet metal oxide micro- and nanocrystallite research. A comprehensive understanding of the properties of metal oxide micro- and nanocrystallites with high-energy crystal surfaces and related synthetic strategies will facilitate the rational design of functional nanomaterials with desired characteristics.

Surface energy for electroluminescent polymers and indium-tin-oxide

Controlled surface modification of Ti–40Nb implant alloy by electrochemically assisted inductively coupled RF plasma oxidation

BackgroundMini dental implants (MDIs) are becoming increasingly popular for rehabilitation of edentulous patients because of their several advantages. However, there is a lack of evidence on the osseointegration potential of the MDIs. The objective of the study was to histomorphometrically evaluate and compare bone apposition on the surface of MDIs and standard implants in a rabbit model.MethodsNine New Zealand white rabbits were used for the study to meet statistical criteria for adequate power. Total 18 3M™ESPE™ MDIs and 18 standard implants (Ankylos® Friadent, Dentsply) were inserted randomly into the tibia of rabbits (four implants per rabbit); animals were sacrificed after a 6-week healing period. The specimens were retrieved en bloc and preserved in 10% formaldehyde solution. Specimens were prepared for embedding in a light cure acrylic resin (Technovit 9100). The most central sagittal histological sections (30–40 μm thick) were obtained using a Leica SP 1600 saw microtome. After staining, the Leica DM2000 microscope was used, the images were captured using Olympus DP72 camera and associated software. Bone implant contact (BIC) was measured using Infinity Analyze software.ResultsAll implants were osseointegrated. Histologic measures show mineralized bone matrix in intimate contact with the implant surface in both groups. The median BIC was 58.5 % (IQR 8.0) in the MDI group and 57.0 % (IQR 5.5) in the control group (P > 0.05; Mann-Whitney test). There were no statistical differences in osseointegration at 6 weeks between MDIs and standard implants in rabbit tibias.ConclusionsBased on these results, it is concluded that osseointegration of MDIs is similar to that of standard implants.

Wetting of a High-Energy Fiber Surface

ABSTRACTDevelopment of surface treatments has enabled secure attachment of dental implants in less than 1 month. Consequently, it is necessary to characterize accurately the osseointegration of the implant surface in the region of the bone-implant contact (BIC). We developed a method for sample preparation that preserves both bone and BIC to permit analysis of the contact interface. We prepared eight nanotextured implants and implanted them in rabbit tibias. After healing for 30 days, outcomes were analyzed using both our bone preservation protocol and routine decalcification followed by preparation of histological sections stained by hematoxylin and eosin (H & E). Pull-out tests for implant osseointegration were performed after healing. Non-implanted samples of rabbit mandible were used as a control for assessing organic and mineralized bone characteristics and bone structure. Our bone preservation protocol enabled evaluation of many of the same bone characteristics as histological sections stained with H & E. Our protocol enables analysis of implant samples, implant surfaces and osseointegration without risk of BIC damage.

Modification of food contacting surfaces by plasma polymerisation technique. Part I: Determination of hydrophilicity, hydrophobicity and surface free energy by contact angle method

Test of favourable conditions for osseointegration with respect to optimum bone-implant contact (BIC) in a loaded animal model. The varied parameters were surface roughness and surface topography of commercially available dental implants. Thirty-two implants of six types of macro and microstructure were included in the study (total 196). The different types were: minimally rough control: Branemark machined Mk III; oxidized surface: TiUnite MkIII and MkIV; ZL Ticer; blasted and etched surface: Straumann SLA; rough control: titanium plasma sprayed (TPS). Sixteen beagle dogs were implanted with the whole set of the above implants. After a healing period of 8 weeks, implants were loaded for 3 months. For the evaluation of the BIC areas, adequately sectioned biopsies were visualized by subsurface scans with confocal laser scanning microscopy (CLSM). The primary statistical analysis testing BIC of the moderately rough implants (mean 56.1+/-13.0%) vs. the minimally rough and the rough controls (mean 53.9+/-11.2%) does not reveal a significant difference (P=0.57). Mean values of 50-70% BIC were found for all implant types. Moderately rough oxidized implants show a median BIC, which is 8% higher than their minimally rough turned counterpart. The intraindividual difference between the TPS and the blasted and etched counterparts revealed no significant difference. The turned and the oxidized implants show median values of the resonance frequency [implant stability quotients (ISQ)] over 60; the nonself-tapping blasted and etched and TPS implants show median values below 60. In conclusion, the benefit of rough surfaces relative to minimally rough ones in this loaded animal model was confirmed histologically. The comparison of different surface treatment modalities revealed no significant differences between the modern moderately rough surfaces. Resonance frequency analysis seems to be influenced in a major part by the transducer used, thus prohibiting the comparison of different implant systems.