SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
The role of thermal spray in medical applications
Rajan Bamola
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
Traditionally, thermal spray in the medical industry has been linked to the
spraying of either titanium or hydroxyapatite on dental, spinal or limb
implants. Generally, these coatings are geared towards Osseo-integration.
This is a restrictive view of the total medical industry and many other
opportunities exist for thermal spray or modified thermal spray.
The objective of the talk is to introduce other non-traditional applications to
the thermal spray industry
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
MEDICAL FIELD
Diagnostic Instruments Surgical Tools Implants
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
Diagnostic Equipment
Miniaturization of diagnostic imaging systems leads to heat build-up in
equipment cases. For example camera housing used for imaging in
endoscopes are made from anodized 6061 Al. The anodized aluminum was
also an effective heat emitter. New aggressive cleaning and sterilization
requirements are causing leaching of the aluminum by the ingestion of
sodium compounds into the porous anodized layer.
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
Internet Image
Endoscope
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
Thermal Emittance of Plasma
Sprayed Alumina Titania
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
Camera Housing sprayed with Sealed Alumina Titania
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
Computer Aided Tomography
A CT scan (computerized tomography scan)[or X-ray computed
tomography (X-ray CT), makes use of computer-processed combinations of
many x-ray images taken from different angles to produce cross-sectional
images (virtual 'slices') of specific areas of a scanned object, allowing the user
to see inside the object without cutting.
Brain Scan
http://en.wikipedia.org/wiki/X-ray_computed_tomography#cite_note-2
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
An integral part of the CAT scan equipment is the x-ray target. These are
housed in vacuum tubes where a heated filament emits electrons which impinge
with high velocity due to a potential difference on the focal track of the target,
99% of electrons energy is converted to heat and 1% creates x-rays. The heat
input creates local temperatures up to 1500C, the target is spun at 10,000RPM
to prevent localized melting of the Tungsten-rhenium layer.
Internet Image
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
The base target constructed from TZM (moly) body and approximately 0.05”
thick focal track of Tungsten Rhenium is constructed via powder metallurgy
press and sinter followed by brazing of the graphite emitting structure. The focal
track is a candidate for LPPS or inductive plasma spray of tungsten rhenium,
this offer repair options of regrinding the track and respray/grind. Because of the
high thermal stresses close to theoretical densities are required for the focal
track with extremely high bond strengths.
Internet Image
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
Tungsten-10%Rhenium Sprayed on 200mm Moly Target
HT 1600C 4Hrs
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
Post Spray Consolidation of Tungsten Rhenium Focal Track on Graphite Target
As Sprayed 1600ºC 4Hrs
1700ºC 4Hrs HIP 1800C 30,000psi 4hrs
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
Electrosurgical tools are a $1B market. Electrical impulses are used to cut and
coagulate tissue during minimally invasive surgery.
Key requirements of the ideal insulator for electro-surgical instruments would
have at least the following characteristics. It should have excellent dielectric
(insulative) properties in the 500 KHZ to 1 MHZ frequency range which is typical
of electro surgery unit generators. In addition, it should have exceptional wear
and abrasion characteristics, and should be impervious to scratching, nicking or
cutting. It should be chemically inert and sterilizable, non-toxic, non-irritating,
and non-cytotoxic.
Ceramic coated
Example internet
Images
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
Electrosurgical Tools
Aluminum Oxide Plasma Sprayed coatings meet these requirements, 0..2-
.003” thick coatings on cutting surfaces applied so just 0.02” of the coating
edge is exposed allows electrical impulses to be directed just at the cutting
edge minimizing patient trauma.
Dielectric BDV (v/mil)
Roughness (RMS μin)
Microhardness (KHN100)
800 140 1050
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
Implants
Implants have been thermally sprayed with Titanium and Hydroxyapatite for
many years. Increasingly shorter healing times have led to research into new
concepts for Osseo-integration
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
Sprayed titanium with PEO (plasma electrolytic oxidation hydroxyapatite). The
microporous HA allows bi-directional bone growth without altering the macro-
texture from Porous Ti spray
CP Ti sprayed with Ti and
PEO HAMicroporosity on Ti particle
with .0004” Calcium
phosphate on TiO2
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
Hydrophilic Surface Conversion of Ti and HA
Ti and plasma sprayed HA coatings are hydrophobic in nature and as so repels
blood. This phenomena slows Osseo-integration. Modifying the surface with
certain bio-compatible ions or creating a certain structure can induce
hydrophillicity attract blood and shorten the diffusion length for proteins to travel
to the implant surface enabling faster and more efficient bone growth.
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
Hydrophilic surface on Ti6Al4V surface
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
SUMMARY
1) Thermal spray coatings can be used for many purposes other then for
orthopedic implants in the medical industry.
2) Not covered here is the possibility to use solution plasma spray to create
drug eluting coatings by dissolving drugs into the solution
3) The next development for implant coatings is to create surface which
further reduce patient recovery times.
SMS Materials Engineering and Coatings Experts
ITSC 2015 Long Beach
YOUR ATTENDANCE WAS KINDLY
APPRECIATED