Abstract: To exploit the impressive electronic, mechanical and thermal properties of Carbon Nanotubes
(CNTs) in the nanoelectronics technology, the development of deposition methods enabling the
synthesis of well ordered, properly located and reproducible CNTs structures, is strongly
recommended. We have been developing catalytic CVD synthesis of CNTs in order to get aligned
nanotubes for applications ranging from nuclear particle-position detectors and cold cathode
emitters for storage devices, to interconnects, vias and CNT-FETs.
In this paper, the significant achievements gained on CVD growth processes for the CNTs
deposition are presented. Ni and Fe catalyst nanoparticles have been obtained starting from thin
films evaporated on silicon based substrates. The growth of vertically aligned carpets of MWNTs
and horizontally aligned SWNTs, having a diameter of about 1 nm and bridging between patterned
catalyst islands, has been accomplished. The SEM, TEM, Raman spectroscopy and AFM
characterizations are discussed.
Abstract: Since preferential orientation of c-axis of biological apatite (BAp) crystallites depends
strongly on the shape of hard tissue, closely relating to the in vivo stress distribution, it is a useful
parameter to judge the bone quality. In this study, preferential alignment of BAp crystallites in original
and regenerated hard tissues were analyzed by the micro-beam X-ray diffractometer (μ-XRD) with a
beam spot of 50 or 100 μm in diameter. Regenerating processes of bone defects introduced artificially
in the rabbit ulna or skull were healed by inserting a biodegradable gelatin hydrogel incorporating
basic fibroblast growth factor-2 (FGF-2).
Recovery of BAp orientation alignment depends strongly on the regenerated portion and period,
which is insufficient to recover the original level, while bone mineral density (BMD) is almost
improved to the original level. This means that BMD recovers prior to improvement of the BAp
orientation and the related mechanical function in the regenerated tissues. Thus, reloading on the
regenerated portion caused by BMD restoration is suggested to accelerate to produce the appropriate
BAp preferential alignment due to the remodeling process.
The BAp orientation was finally concluded to be one of the most important indices to check the
regenerative degree and process in the regenerated bone under the tissue engineering technique.
Abstract: Fretting fatigue is a form of adhesive wear damage caused due to tangential micro motion of
two contact bodies under normal pressure and cyclic load. Biomedical implants such as hip joints
and bone plates undergo fretting fatigue damage leading to premature in-vivo failure and revision
surgeries. Surface modification of implants delays the process of fretting and thereby improves the
life of these medical devices. This work involves investigation of fretting fatigue damage of surface
treated titanium alloys couple. The surface treatment involves PVD TiN coating, Plasma nitriding,
Ion Implantation, Laser nitriding and thermal oxidation. Fretting of all surface treated alloys have
shown both adhesive and abrasive mode of contact damage. Friction coefficient of all the surface
treated pairs is less compared to uncoated alloys. Plasma nitrided pairs have shown the best
performance in terms of fretting fatigue life and friction coefficient compared to all other coatings.
Ion implanted pairs have shown little improvement in fretting fatigue lives due to shallow modified
layer. PVD TiN coated pairs have irregular friction pattern due to abrasive particles at contact.
Thermal oxidation and Laser nitriding have shown poor fretting fatigue performance due to high
Abstract: Hydroxyapatite (Ca10(PO4)6(OH)2, HAp), carbonated HAp and titanium oxide are of
interest for bone-interfacing implant applications, because of their demonstrated osteoconductive
properties. They were coated on the titanium implants and investigated the in vitro and in vivo
performance. HAp coatings were performed by the thermal substrate method in aqueous solutions.
Titanium oxide film was also formed on the titanium implants by gaseous oxidation, or by anodizing
in the acidic solution. All the specimens covered with HAp, carbonated HAp or TiO2 (rutile or
anatase). were characterized by XRD, EDX, FT-IR and SEM. In the in vitro testing, the mouse
osteoblast-like cells (MC3T3-E1) were cultured on the coated and non-coated specimens for up to 30
days. Moreover, the osseointegration was evaluated from the rod specimens implanted in rats
femoral for up to 8 weeks. In in vivo evaluations two weeks postimplantation, new bone formed on
the coated and non-coated titanium rods in the cancellous bone and cortical bone, respectively.
Bone-implant contact ratio, in order to evaluate of new bone formation, was significantly depended
on the compound formed on the titanium implant.
Abstract: A brief description of the uses and clinical applications of synthetic
cyanoacrylate polymer adhesive/glues that have been cleared and/or approved as medical
devices by FDA since the Medical Device Amendments of 1976 were enacted. This
includes cyanoacrylate Class I devices (Exempt and not Exempt devices), Class II
cyanoacrylate devices such as Dental Cements and Orthodontic Bracket Adhesives, and
Class III (PMA) devices such as Dermabond™, Indermil™ Tissue Adhesive, and
Trufill® n-Butyl Cyanoacrylate Embolic Agent. By citing an example of recently FDA
approved Class III (PMA) devices in the Cyanoacrylate technology, the author provides a
brief discussion of the FDA approval process of medical devices. It includes the FDA
issues regarding the published guidance document for "Cyanoacrylate Topical Tissue
Adhesives" that will provide guidance to regulatory personnel and manufacturers in the
preparation of IDE applications and in the development of valid scientific evidence to
support PMA applications for cyanocrylate tissue adhesives intended for topical
approximation of skin and others. Also, the author provides a short regulatory
description of US FDA; under what laws its operates, how FDA evaluates new devices
for marketing, and how the device regulatory system works, for example, Class I, Class
II, and Class III cyanoacrylate medical devices.
Abstract: Metal alloys containing chromium (Cr), primarily stainless steels and CoCr alloys, are
used in a wide variety of implantable medical devices. These alloys are exposed to chloride
containing environments with varying oxidizing potential and complexing agents. These corrosion
assisted environmental effects may result in metal ions going into solution. The toxicity of Cr is
dependent on valence state. Hexavalent Cr ions are recognized to be more toxic than trivalent Cr.
This paper discusses the state of knowledge regarding Cr release, the chemical and mechanical
factors that most significantly affect Cr release, and the potential toxicity of Cr as it applies to longterm
implantable medical devices.
Abstract: Hydroxyapatite (HAp) coatings were formed on cp titanium plates and rods by the
thermal substrate method in an aqueous solution that included 0.3 mM Ca(H2PO4)2 and 0.7 mM
CaCl2. The coating experiments were conducted at 40-140 oC and pH = 8 for 15 or 30 min. The
properties for the coated samples were studied using XRD, EDX, FT-IR, and SEM. All the specimens
were covered with HAp, which had different surface morphologies such as net-like, plate-like and
needle-like. After cleaning and sterilization, all the coated specimens were subjected to in vivo and
vitro testing. In the in vitro testing, the mouse osteoblast-like cells (MC3T3-E1) were cultured on the
coated and non-coated specimens for up to 30 days. Moreover, the specimens (φ2 x 5 mm) were
implanted in rats femoral for up to 8 weeks, the osseoinductivity on them were evaluated. In in vitro
evaluations, there were not significant differences between the different surface morphologies. In in
vivo evaluations, however, two weeks postimplantation, new bone formed on both the HAp coated
and non-coated titanium rods in the cancellous and cortical bone. The bone-implant contact ratio,
which was used for the evaluation of new bone formation, was significantly dependent on the surface
morphology of the HAp, and the results demonstrated that the needle-like coating appears to promote
rapid bone formation.
Abstract: Formation of crystallographically orientaed hydroxyapatite (HAp) is one of the promising
ways to utilize their anisotropic nature of chemical and biological properties. On the other hand, the
development of super conducting magnet technology enables to introduce a high magnetic field
which can control crystal orientation of non-magnetic materials with magnetic anisotropy. In this
study, a high magnetic field and sample rotation are simultaneously imposed on the hydroxyapatite
during a slip casting process in order to align its c-plane within a horizontal plane. From X-ray
diffraction, it has been found that the HAp crystals in the sample treated with the magnetic field and
the sample rotation were oriented to a particular direction in the slip casting process and it was
enhanced by the subsequent sintering process, while the c-axis crystal orientation of the sample
treated without the magnetic field and with the sample rotation was not observed before and after the
Abstract: Highly porous titanium and titanium alloys with an open cell structure are promising
implant materials due to their low elastic modulus, excellent bioactivity, biocompatibility and the
ability for bone regeneration. However, the mechanical strength of the porous titanium decreases
dramatically with increasing porosity, which is a prerequisite for the ingrowth of new bone tissues
and vascularization. In the present study, porous titanium with porosity gradients, i.e. solid core with
highly porous outer shell was successfully fabricated using a powder metallurgy approach.
Satisfactory mechanical properties derived from the solid core and osseointegration capacity derived
from the outer shell can be achieved simultaneously through the design of the porosity gradients of
the porous titanium. The outer shell of porous titanium exhibited a porous architecture very close to
that of natural bone, i.e. a porosity of 70% and pore size distribution in the range of 200 - 500 μm. The
peak stress and the elastic modulus of the porous titanium with a porosity gradient (an overall
porosity 63%) under compression were approximately 152 MPa and 4 GPa, respectively. These
properties are very close to those of natural bone. For comparison, porous titanium with a uniform
porosity of 63% was also prepared and characterised in the present study. The peak stress and the
elastic modulus were 109 MPa and 4 GPa, respectively. The topography of the porous titanium
affected the mechanical properties significantly.