Upload
others
View
3
Download
0
Embed Size (px)
Citation preview
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
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
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 (Sculptured Thin Films)
Rotate abouty axis fornematicmorphology
Rotate aboutz axis forhelicoidalmorphology
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
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
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