Nanoengineered Materialsfor

Surgical Coatings

Akhlesh LakhtakiaDepartment of Engineering Science & Mechanics

Pennsylvania State University

Surgical Coatings: Examples

• Surgical implements (cautery points, scalpels,scissors)

• Surgical pumps (inner linings of suction pumps)

• Surgical textiles (masks, drapes, and gowns)

• Surgical cover sheets (internal & externaluses)

Surgical Coatings

Common requirements:

1. Tissue-repellent2. Bacterium-repellent3. Pathogen-repellent

Surgical Coatings

Common requirements:

1. Tissue-repellent2. Bacterium-repellent3. Pathogen-repellent

Water-repellent

Water-repellent surfaces

More repellent Less repellent

Strategies for WaterRepellence

• Ciliated structures• Fluorinated surfaces and volumes

Ciliated Structures

Surface of a plant leaf

Butterfly wing

Natural

Natural

Ciliated Structures

Lithographically patterned siliconArtificial

Fluorinated SurfacesTeflon

Fluorinated Surfaces

Polyethylene, teflon, hydrocarbon oils, etc. Low-energy surfaces in airDifficult to contaminate

Strategies for WaterRepellence

• Ciliated structures• Fluorinated surfaces and volumes

• Combination strategy

Combination Strategy:

Sculptured Thin Filmsof Fluorinated Parylene

Sculptured Thin Films

Nano 50 Awardfor Technology (2005)

Nano 50 Awardfor Innovation (2006)

Sculptured Thin Films

Sculptured Thin Films

Sculptured Thin Films

Sculptured Thin Films

Morphology change in 3-5 nm

Sculptured Thin FilmsAssemblies of Parallel Curved Nanowires/Submicronwires

Controllable Nanowire Shape

2-D - nematic3-D - helicoidalcombination morphologiesvertical sectioning

Nanoengineered Materials (1-3 nm clusters)

Controllable Porosity (10-90 %)

Physical Vapor Deposition (Columnar Thin Films)

Physical Vapor Deposition (Sculptured Thin Films)

Rotate abouty axis fornematicmorphology

Rotate aboutz axis forhelicoidalmorphology

Physical Vapor Deposition (Sculptured Thin Films)

Sculptured Thin FilmsOptical Devices: Polarization Filters

Bragg FiltersUltranarrowband FiltersFluid Concentration SensorsBacterial Sensors

Biomedical Applications: Tissue ScaffoldsDrug/Gene DeliveryBone RepairVirus Traps

Other Applications: PhotocatalysisThermal BarriersEnergy Harvesting

Parylene C

• FDA-approved polymer

• Low-molecular-weightdimer of para-chloro-xylylene

Also called: [2.2] paracyclophane

Parylene C• Vaporizes in vacuum at 150 deg C

• Monomerizes at 680 deg C

Both properties are exploited for depositing Parylene-CSTFs

Parylene C: Thermal Stabilityand Biosafety

• Insoluble in all organic solvents upto 150 degC

• Stable under continuous exposure to air at 10deg C for 10 years

• No known biological degradation mechanismsor pathways

Parylene C: Medical Safety• Nontoxic to cells (negative cytotoxicity)

• Does not coagulate blood (nonthrombogenic)

• No known biological degradation mechanisms orpathways

• Nontoxic to skin (negative intracutaneous toxicity)

• Caution: Repeated aerosol exposure results inlaryngitis

Traditional Applications of Parylene

• SurgicalInstruments

• Pacemakers• Catheters• Sensors• Stents• Biomedical

devices• Forceps• Needles

• Fiber OpticComponents

• HeatExchangers

• Hybrids• Relays• Power

Supplies• Magnets• Cores• Seals• Capacitors• PWBs

• Probes• Photoelectric Cells• Elastomers• Circuit Boards• Semiconductors• Metal Components• Keypads• Gaskets• Bobbins

PARYLENE-C STFs:COMBINED CVD+PVD TECHNIQUE

PARYLENE-C STFs:COMBINED CVD+PVD TECHNIQUE

1. Vaporize the dimer at 150 deg C2. Monomerize at 680 deg C3. Release the monomer vapor through a nozzle towards a substrate4. Polymerization into ciliated structures

PARYLENE-C STFs:Nanoengineered Ciliated Structure

NanoscaleMorphology

Ciliated structure

Volumetric FluorinationInstead of

Carry out Friedel-Crafts acylation, and then the PVD+CVD

Other fluorination schemes can be devised.

Surface FluorinationDeposit Parylene-C using PVD+CVD

Then implement chemisorption with, say, fluoroalkyltrichlorosilane

Other fluorination schemes can be devised.

Contact angle measurements

Parylene-C STF 100 deg

Fluorinated Parylene-C 88 deg(not STF)

FluorinatedParylene-C STF 133 deg

The larger the contact angle, the more water-repellence

Contact angle measurements

FluorinatedParylene-C STF 133 deg

The larger the contact angle, the more water-repellence

Gore-Tex ePTFE 100-120 deg

Heat Treatment 140 deg

More Work

Optimization:1. Ciliar geometry, thickness, and density2. Fluorination pathway3. Rapid production of textiles4. Rapid coating of medical implements