Search

Polyether ether ketone (PEEK) rods were coated via ion beam asssited deposition (IBAD) at room temperature. The coating consists of a two-layer design of yttria-stabilized zirconia (YSZ) as a heat-protection layer, and hydroxyapatite (HA) as a top layer to increase bioactivity. A rotating substrate holder was designed to deposit an even coating on the cylindrical surface of PEEK rods; the uniformity is verified by cross-sectional measurements using scanning electron microscopy (SEM). Deposition is followed by heat treatment of the coating using microwave annealing and autoclaving. Transmission electron microscopy (TEM) showed a dense, uniform columnar grain structure in the YSZ layer that is well bonded to the PEEK substrate, while the calcium phosphate layer was amorphous and pore-free in its as-deposited state. Subsequent heat treatment via microwave energy introduced HA crystallization in the calcium phosphate layer and additional autoclaving further expanded the crystallization of the HA layer. Chemical composition evaluation of the coating indicated the Ca/P ratios of the HA layer to be near that of stoichiometric HA, with minor variations through the HA layer thickness. The adhesion strength of as-deposited HA/YSZ coatings on smooth, polished PEEK surfaces was mostly unaffected by microwave heat treatment, but decreased with additional autoclave treatment. Increasing surface roughness showed improvement of bond strength.

Polyether ether ketone (PEEK) is a highly heat-resistant thermoplastic with excellent strength and elastic modulus similar to human bone, making it an attractive material for orthopedic implants. However, the hydrophobic surface of PEEK implants induces fibrous encapsulation which is unfavorable for stable implant anchorage. In this study, PEEK was coated via ion-beam-assisted deposition (IBAD) using a two-layer design of yttria-stabilized zirconia (YSZ) as a heat-protection layer, and hydroxyapatite (HA) as a top layer to improve osseointegration. Microstructural analysis of the coatings showed a dense, uniform columnar grain structure in the YSZ layer and no delamination from the substrate. The HA layer was found to be amorphous and free of porosities in its as-deposited state. Subsequent heat treatment via microwave energy followed by autoclaving crystallized the HA layer, confirmed by SEM and XRD analysis. An in vitro study using MC3T3 preosteoblast cells showed improved bioactivity in heat-treated sample groups. Cell proliferation, differentiation, and mineralization were analyzed by MTT assay and DNA content, osteocalcin expression, and Alizarin Red S (AR-S) content, respectively. Initial cell growth was increased, and osteogenic maturation and mineralization were accelerated most on coatings that underwent a combined microwave and autoclave heat treatment process as compared to uncoated PEEK and amorphous HA surfaces. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 560-567, 2017.

We report three representative nanowire (NW) devices for applications in stretchable electronics, strain sensing, and optical sensing. Fabrication of such devices is based on a recently developed strain-release assembly method. NWs are first aligned transversely on an elastomeric substrate using the strain-release assembly. Constant resistance is achieved in silicon (Si) NW devices stretched up to ~40% of axial strain, highlighting a new concept of transverse buckling. Combining the NW assembly with transfer printing extends suitable device substrates beyond elastomers to other unconventional materials (e.g., flexible and transparent materials). Following this combined process, flexible SiNW strain sensors are fabricated on plastics capable of sensing up to 1.6% bending strain and gauge factors1000; flexible zinc oxide NW ultraviolet sensors are demonstrated with quick recovery (~2 s) and excellent repeatability on plastics. Our results show promise for the strain-release assembly as a simple and cost-effective process to fabricate NW devices on unconventional substrates.

A bioactive two-layer coating consisting of hydroxyapatite (HA) and yttria-stabilized zirconia (YSZ) was investigated on cylindrical polyetheretherketone (PEEK) implants using ion beam assisted deposition (IBAD). Post-deposition heat treatments via variable frequency microwave annealing with and without subsequent autoclaving were used to crystallize the as-deposited amorphous HA layer. Microstructural analysis, performed by TEM and EDS, showed that these methods were capable of crystallizing HA coating on PEEK. The in vivo response to cylindrical PEEK samples with and without coating was studied by implanting uncoated PEEK and coated PEEK implants in the lateral femoral condyle of 18 rabbits. Animals were studied in two groups of 9 for observation at 6 or 18weeks post surgery. Micro-CT analysis, histology, and mechanical pull-out tests were performed to determine the effect of the coating on osseointegration. The heat-treated HA/YSZ coatings showed improved implant fixation as well as higher bone regeneration and bone-implant contact area compared to uncoated PEEK. The study offers a novel method to coat PEEK implants with improved osseointegration.

Polyether ether ketone (PEEK) is a highly heat-resistant thermoplastic with excellent strength and elastic modulus similar to human bone, making it an attractive material for orthopedic implants. However, the hydrophobic surface of PEEK implants induces fibrous encapsulation which is unfavorable for stable implant anchorage. In this study, PEEK was coated via ion-beam-assisted deposition (IBAD) using a two-layer design of yttria-stabilized zirconia (YSZ) as a heat-protection layer, and hydroxyapatite (HA) as a top layer to improve osseointegration. Microstructural analysis of the coatings showed a dense, uniform columnar grain structure in the YSZ layer and no delamination from the substrate. The HA layer was found to be amorphous and free of porosities in its as-deposited state. Subsequent heat treatment via microwave energy followed by autoclaving crystallized the HA layer, confirmed by SEM and XRD analysis. An in vitro study using MC3T3 preosteoblast cells showed improved bioactivity in heat-treated sample groups. Cell proliferation, differentiation, and mineralization were analyzed by MTT assay and DNA content, osteocalcin expression, and Alizarin Red S (AR-S) content, respectively. Initial cell growth was increased, and osteogenic maturation and mineralization were accelerated most on coatings that underwent a combined microwave and autoclave heat treatment process as compared to uncoated PEEK and amorphous HA surfaces. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 560-567, 2017.

A simple yet effective method for assembly of highly aligned nanowires (NWs) on stretchable substrates is reported. In this method, NWs were first transferred to a strained stretchable substrate. After the strain was released, the NWs aligned in the transverse direction and the area coverage of the NWs on the substrate increased. This method can be applied to any NWs deposited on a stretchable film and can be repeated multiple times to increase the alignment and density of the NWs. For silver (Ag) and silicon (Si) NWs on poly(dimethylsiloxane) (PDMS) substrates, the probability of NW alignment increased from 29% to 90% for Ag NWs, and from 25% to 88% for Si NWs after two assembly steps; the density increased by 60% and 75% for the Ag and Si NWs, respectively. The large-strain elasticity of the substrate and the static friction between the NWs and the substrate play key roles in this assembly method. We find that a model that takes into account the volume incompressibility of PDMS reliably predicts the degree of NW alignment and NW density. The utility of this assembly method was demonstrated by fabricating a strain sensor array composed of aligned Si NWs on a PDMS substrate, with a device yield of 95%.

The general adoption of “Arabic” numerals by European bookkeepers occurred at least five hundred years after their introduction to the scholarly world. The early availability yet late adoption of this numeration is shown to be due to several factors, not least to interplay between the culture and cultural conservatism of clerks and the educational and intellectual changes of the early Italian Renaissance.

Eighteen patients were treated surgically for injuries to the radial collateral ligament of the thumb metacarpophalangeal joint. Late repairs were performed in 12 and immediate repairs in 6. At follow-up after a mean of 6 years, 94% of the patients were completely satisfied with the results. No patients had significant pain in their thumbs, and none were limited in work or avocational activities. A stable repair was maintained in all patients. There was no difference in grip or pinch strengths between the immediate and late groups. Loss of thumb motion in the late group (mean = 77% of normal) was slightly more than that in the immediate group (mean = 89% of normal). Late repair gives equally good subjective results and causes a slightly greater loss of thumb motion than immediate repair.

Surface electrical stimulation using the ScoliTron™ device was applied to 40 adolescent patients for treatment of idiopathic scoliosis. Adequate follow-up was available for 30 of these patients. The overall failure rate was 15 of 30 or 50%. Due to curve progression while using the ScoliTron, these patients either went on to a fusion (9 of 15) or were changed to a brace (6 of 15). The remaining 15 patients were considered successes with no curve progression (10 of 30 or 33%) or successful/failures with slight curve progression not requiring a change in treatment (5 of 30 or 17%). None of the various parameters analyzed were found to be useful indicators of successful treatment using the ScoliTron device. Electrical stimulation was found to be ineffective in preventing curve progression for idiopathic scoliosis.

Bij veertig jeugdige patienten werd ter behandeling van idiopathische scoliose elektrostimulatie met oppervlakte-elektroden toegepast met een Scoli-Tron-apparaat. Dertig van deze patienten konden gedurende vier jaar worden gevolgd. Bij vijftien van deze dertig patienten (50%) was sprake van mislukking. In verband met de progressie van de curve gedurende de tijd dat de ScoliTron werd gebruikt, werd bij deze patienten overgegaan tot operatieve fusie (9 van de 15), of gebruik van een beugel (6 van de 15).