View abstract View article PDF Due to their excellent biodegradability characteristics, Mg and Mg-based alloys have become an emerging material in biomedical implants, notably for repair of bone as well as coronary arterial stents.
San Francisco and U. Ashby Find articles by Paul D. Received Sep 12; Accepted Nov 4. One strategy for reducing wear particle formation from UHMWPE is to modify the surface with a hydrophilic coating to increase lubrication from synovial fluid. This study focuses on the wear behavior of hydrophilic coatings similar to poly ethylene glycol PEG.
Introduction The long-term success of total hip replacements THRs depends on a number of factors, including implant design, surgical skill, and infection rates. However, the most common cause of late-stage THR failure is wear-mediated osteolysis, an immune response to wear particles from the articulating surfaces that results in pain, bone loss, and implant loosening [ 12 ].
The predominant strategy to improve THR longevity is to reduce wear particle formation. In the past decade, much effort has focused on the use of irradiation schemes to provide bulk crosslinking in order to improve the wear behavior of UHMWPE [ 45 ]; however, this approach renders the polymer susceptible to decreased fracture resistance [ 67 ].
An alternative solution to decrease wear particle formation from UHMWPE is to modify only the surface, rather than the bulk, and one approach is to coat the surface with a lubricious hydrogel [ 8 — 10 ].
We have developed a coating made of plasma-polymerized tetraglyme, an oligomer similar to poly ethylene glycol PEG [ 11 ]. Unlike other hydrogel coatings that have been examined to date, this coating is both crosslinked and covalently bonded to the UHMWPE surface.
Crosslinking should increase the structural integrity of the coatings, enabling them to resist wear-induced surface damage. For this reason, care was taken to assess the relative crosslink density of the coatings. This study utilized a number of surface characterization methods, including X-ray photoelectron spectroscopy XPSinfrared spectroscopy, contact angle measurement, and crosslink density assessment, along with atomic force microscopy AFM wear testing, in order to evaluate the micron-scale wear behavior of PEG-like coatings on UHMWPE.
AFM nanoscratching, which allows for both imaging and quantification of surface damage, was chosen to simulate asperity wear and identify the predominant wear behavior s of the coatings. This work elucidates the relationship between observed wear modes and crosslinking at the bearing surface and facilitates a pathway for developing wear-resistant surface treatments for UHMWPE used in THRs.
For each plasma deposition batch, survey and high-resolution C 1s spectra were collected at two spots on two samples. Contact angle goniometry The relative hydrophilicity of the surfaces was measured using a custom-made contact angle goniometer with a variable-magnification InfiniVar video microscope Infinity Photo-Optical Co.
Two spots on two samples per plasma deposition batch were tested. This method is discussed in more detail elsewhere [ 12 ].
Atomic force microscopy scratch testing AFM nanoscratching was used to evaluate the microscale wear behavior of the coatings. The surface was re-imaged after lithography which was omitted from some sequences to evaluate the behavior of fully intact coatings and again after every 1—4 scratches.
During scratching, the AFM also recorded images, which show the real-time scratching behavior of the coatings.The equations of rocketry dictate that two primary numbers decide a vehicles ability to get into orbit: Specific Impulse, or Isp, which is the pound-seconds of thrust per pound of vehicle carried propellant expended, i.e.
a measure of the fuel efficiency of the propulsion system, and Mass Fraction, which is the ratio of propellant carried by a launch vehicle to the total launch mass (airframe.
of biotribology experiments has improved a lot during this period and we focus on recent development of coating materials. Wear of the ceramic materials is substantially (two orders of magnitude) lesser than that of PE, and the wear of the carbon coating is several times . Since the two-body wear rate is much higher than the three-body wear, the wear rate of steel became much higher than the wear rate of ATSP coating, shown in Fig.
4(b). However, in the places where deep scratches formed in stage A, there were absent of ATSP coating that could hold and press the sand on the steel pin. Research interests. Professor Robert Wood has research interests that span the application of lubrication, wear and friction science to current and next generation critical machine components such as bearings, transmissions, turbines, pumps and oil and gas drills.
A chemical formula is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using a single line of chemical element symbols and numbers. Now open for submissions, Electronic Structure is a new, multidisciplinary journal for the entire electronic structure community, bridging physics, chemistry, materials science, and biology All papers published in the first volume of the journal will be free to read throughout