The role of thermal spray in medical applications

Transcription

1 The role of thermal spray in medical applications Rajan Bamola

2 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

3 MEDICAL FIELD Diagnostic Instruments Surgical Tools Implants

4 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.

5 Endoscope Internet Image

6 Thermal Emittance of Plasma Sprayed Alumina Titania

7 Camera Housing sprayed with Sealed Alumina Titania

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9 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

10 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

11 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.

12 Tungsten-10%Rhenium Sprayed on 200mm Moly Target HT 1600C 4Hrs

13 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

14 Electrosurgical tools are a $1B market. Electrical impulses are used to cut and coagulate tissue during minimally invasive surgery. Ceramic coated Example internet Images 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.

15 Electrosurgical Tools Aluminum Oxide Plasma Sprayed coatings meet these requirements, 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)

16 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

17 Sprayed titanium with PEO (plasma electrolytic oxidation hydroxyapatite). The microporous HA allows bi-directional bone growth without altering the macrotexture from Porous Ti spray CP Ti sprayed with Ti and PEO HA Microporosity on Ti particle with.0004 Calcium phosphate on TiO 2

18 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.

19 Hydrophilic surface on Ti6Al4V surface

20 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.

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