Sputter deposited hydroxyapatite thin films to enhance osseointegration

Department Head: Allan Thomson Kirkpatrick.2010 Spring.Includes bibliographical references (pages 62-64).As the demand for hip and knee replacements continues to grow, researchers look to increase the operational lifetimes of these implants. Many of these implants fail as a result of aseptic loosening caused from repeated loading of these joints. It is thought that implant life could be extended by improving the interface between the implant and natural tissue. To this effect, hydroxyapatite coatings have been demonstrated to improve implant to bone bonding and allow a more natural integration of the metallic substrates. This work explores the potential of using ion beam etching and sputter deposition to produce a hydroxyapatite thin film with a unique surface topography that would potentially enhance osseointegration. First, the effects of ion etching bare titanium were evaluated. Three ion energies (300 eV, 700 eV, and 1100 eV) were used to etch either as-received or polished substrates. Topographical changes were examined by scanning electron microscopy. Rat mesenchymal stem cells were differentiated to osteoblasts to test the biocompatibility of the surfaces with bone cells. It was found that ion etching the titanium increases cellular activity, and an ion energy of 700 eV appears to create the most beneficial topography. Hydroxyapatite thin films were then sputter deposited on titanium substrates etched at 700 eV. After the coatings were deposited, some of the hydroxyapatite films were re-etched in efforts to induce a unique topography. It was found that the hydroxyapatite coatings improved short term cell response but degraded over the course of the culture. Further investigation showed the as-sputtered coatings were amorphous. To prevent degradation of the coatings, annealed films were then prepared by heat treating at 600 °C for 2 hours. X-ray diffraction was used to confirm the presence of a crystalline hydroxyapatite phase. Films were immersed in culture media for four weeks, showing no signs of degradation. Ion etching performed on the substrates post annealing yielded a unique topography in the hydroxyapatite film. A final study was conducted evaluating the MSC response to the annealed and post-anneal etched films. It was found that the post-anneal etched hydroxyapatite coating had the highest cellular activity, indicating that this preparation may be an effective means to enhance osseointegration on medical implants

Plasma processing for nanostructured topographies

2012 Spring.Includes bibliographical references.Plasma and directed ion interactions with materials have been widely observed to create complex surface patterns on a micro- and nano- scale. Generally, these texturizations are byproducts of another intended application (such as a feature formation on a sputtering target) and patterning is considered inconsequential or even detrimental. This work examined the possibility of using these phenomena as primary methods for producing beneficial topographies. Specifically, investigations focused on the use of helium plasma exposure and directed ion etching to create nanostructured surfaces capable of affecting biological interactions with implanted materials. Orthogonal argon ion etching and low energy helium plasma texturization of titanium were considered for use on orthopedic and dental implants as a means of increasing osteoblast activity and bone attachment; and oblique angle etching was evaluated for its use in creating topographies with cell deterrent or anti-thrombogenic properties. In addition, the helium driven evolution of surface features on 6061 aluminum alloy was characterized with respect to ion energy and substrate temperature. These surfaces were then considered for ice phobic applications

Long-term tropospheric formaldehyde concentrations deduced from ground-based fourier transform solar infrared measurements

We report a 13-year (1992–2005) dataset of total column measurements of formaldehyde (HCHO) over Lauder, New Zealand, inferred from solar infrared spectra measured using a high-resolution Fourier Transform Spectrometer (FTS). Ambient HCHO concentrations at this rural location are often close to levels typical of remote marine environments (\u3c250 ppt), which are close to the detection limit using standard techniques. Consequently we develop a new method that successfully produces HCHO columns with sufficient sensitivity throughout the whole season. HCHO columns over Lauder have a strong seasonal cycle (±50%), with a mean column of 4.9×1015 molecules cm−2, peaking during summer months. A simple box model of CH4 oxidation reproduces the observed broad-scale seasonal cycle, but significantly underestimates the seasonal peak HCHO ground concentrations during summer. This suggests the existence of an additional significant source of HCHO, possibly isoprene that cannot be explained by oxidation of CH4 alone. The ground-based FTS column data compare well with collocated HCHO column measurements from the Global Ozone Monitoring Experiment (GOME) satellite instrument during the operational period of GOME (1996–2001, r2=0.65, mean bias=10%, n=48)

SNR Study of Outdoor Electroluminescence Images under High Sun Irradiation

Electroluminescence (EL) imaging inspections of PV power plants can bring a huge improvement in accuracy. The use of InGaAs camera will also make such inspections fast, but the restriction to acquire the images during dusk or evening is a limitation. Performing lock-in EL is a way to go for daylight EL. This paper proposes an extension of the SNR50 quality measure to estimate the quality of a stack of N images and evaluates the impact of some factors over the measured and visual quality of images acquired with InGaAs sensors. The factors analyzed are the characteristics of the noise in the acquired images, the influence of the sun variations and the averaging over multiple acquired images

A Quantum Photonic Interface for Tin-Vacancy Centers in Diamond

The realization of quantum networks critically depends on establishing efficient, coherent light-matter interfaces. Optically active spins in diamond have emerged as promising quantum nodes based on their spin-selective optical transitions, long-lived spin ground states, and potential for integration with nanophotonics. Tin-vacancy (SnV$^{\,\textrm{-}}$) centers in diamond are of particular interest because they exhibit narrow-linewidth emission in nanostructures and possess long spin coherence times at temperatures above 1 K. However, a nanophotonic interface for SnV$^{\,\textrm{-}}$ centers has not yet been realized. Here, we report cavity enhancement of the emission of SnV$^{\,\textrm{-}}$ centers in diamond. We integrate SnV$^{\,\textrm{-}}$ centers into one-dimensional photonic crystal resonators and observe a 40-fold increase in emission intensity. The Purcell factor of the coupled system is 25, resulting in channeling of the majority of photons ($90\%$) into the cavity mode. Our results pave the way for the creation of efficient, scalable spin-photon interfaces based on SnV$^{\,\textrm{-}}$ centers in diamond