The role of thermal spray in medical applications Role of Thermal Spray in Medical...Traditionally, thermal spray in the medical industry has been linked to the spraying of either

SMS Materials Engineering and Coatings Experts

ITSC 2015 Long Beach

The role of thermal spray in medical applications

Rajan Bamola



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



MEDICAL FIELD

Diagnostic Instruments Surgical Tools Implants



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.



Internet Image

Endoscope



Thermal Emittance of Plasma

Sprayed Alumina Titania



Camera Housing sprayed with Sealed Alumina Titania



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



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



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



Tungsten-10%Rhenium Sprayed on 200mm Moly Target

HT 1600C 4Hrs



Post Spray Consolidation of Tungsten Rhenium Focal Track on Graphite Target

As Sprayed 1600ºC 4Hrs

1700ºC 4Hrs HIP 1800C 30,000psi 4hrs



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



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



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



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



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.



Hydrophilic surface on Ti6Al4V surface



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.



YOUR ATTENDANCE WAS KINDLY

APPRECIATED

Documents

The role of thermal spray in medical applications Role of Thermal Spray in Medical...Traditionally, thermal spray in the medical industry has been linked to the spraying of either