MSE 536- SP2025_Surface Properties and Modifications

Page 1: Overview

• Course: MSE 536 - Advanced Biomaterials

• Focus: Surface Properties and Modifications

Page 2: Importance of Surface Properties

• Biomaterial Surface: Crucial for biological response and implant success.

• Adsorption: Adhesion of molecules (ions, water, proteins) to solid surfaces.

  • At physiological conditions, these adsorbates impact biological response.

• Controlling Protein Adsorption: Vital as the body interacts with the coated surface.

• Surface Characteristics Change Over Time: Due to coating degradation or substrate changes.

• Biological Surface Modification Techniques:

  • Covalent coatings (plasma discharge, CVD, radiation grafting)

  • Noncovalent coatings (solution coating, LB films)

  • No overcoat techniques (ion beam, plasma treatment, conversion coatings)

Page 3: Key Surface Properties

1. Surface Hydrophobicity:

   • Determines water repellence of materials.

   • Synthetic polymers are typically hydrophobic, ceramics and metals are often more hydrophilic.

   • Protein adsorption increases with surface hydrophobicity.

2. Surface Charge:

   • Significant charges can attract or repel charged protein areas.

   • Charge affects contact angle and hydrophobicity comparisons.

   • Material B has a higher contact angle than Material A, indicating greater hydrophobicity.

Page 4: Wettability

• Definition: Liquid spreadability on solid surfaces;

• Contact Angle: Measures wettability.

  • 0°: Complete wettability.

  • 180°: Non-wettable surface.

• Photomicrographs illustrate hydrophilic vs. hydrophobic surfaces.

Page 5: Contact Angle Analysis

• Contact Angle (!) Measurement:

  • Relation among liquid-vapor, solid-liquid, and solid-vapor surface tensions.

  • Used in surface characterization.

• Wettability Change: Surface modifications can reduce the contact angle as water droplets spread more.

Page 6: Advanced Contact Angle Measurements

• Measurement Process:

  1. Advanced contact angle measurement.

  2. Receded contact angle measurement.

  3. Contact angle hysteresis assessment.

• Low hysteresis: Homogeneous surface.

• High hysteresis: Heterogeneous surface.

Page 7: Surface Characterization Techniques

• Goal: Assess surface treatment quality and protein adsorption levels.

Page 8: Physical Characteristics of Biomaterials

1. Steric Repulsion:

   • Flexible hydrophilic polymer chains block protein attachment.

2. Surface Roughness:

   • Encourages protein trapping in surface valleys.

Page 9: Biomaterial Surface Modification

• Herbs affect hydrophobicity, charge, steric hindrance, or roughness of surfaces.

• Ideal modifications should be:

  1. Thin

  2. Resistant to delamination

  3. Simple and robust

Page 10: Surface Modification Techniques

1. Physicochemical Modifications:

   • Changes surface composition without biological molecules.

   • Types: Covalent surface coatings, non-covalent coatings, no overcoat.

2. Biological Modifications:

   • Involve biologically active molecule attachment.

   • Types: Covalent and non-covalent biological coatings.

Page 11: Surface Modification Techniques and Materials

• Overview of non-covalent and covalent techniques along with applicable materials.

Page 12: Summary of Modification Methods

• Detailed breakdown of physicochemical surface modification methods across categories.

Page 13: Covalent Surface Coatings

• Focus on covalent modification methods.

Page 14: Plasma Treatment

• Definition: A gas environment containing ions, radicals, and electrons.

• Applications: Cleaning, hydroxyl/amine addition, polymerizing molecules, and coating application.

Page 15: Plasma Discharge Treatment Process

• Detailed mechanism illustrating electron gas interactions and resultant surface reactions.

Page 16: Advantages and Disadvantages of Plasma Treatment

• Advantages:

  • Conformal, sterilized, good adhesion, unique chemistries.

• Disadvantages:

  • Undefined chemistry, expensive equipment, uniformity issues in complex geometries.

Page 17: Chemical Vapor Deposition (CVD)

• Process: High-temperature gas exposure causes deposition on substrates via thermal decomposition.

Page 18: Physical Vapor Deposition (PVD)

• Involves physical processes to deposit atoms, enhancing wear resistance.

• Method: Sputtering, plasma assistance.

Page 19: Radiation Grafting/Photografting

• Principle: Use of radiation to create reactive species for covalent binding.

• Details on mutual and photografting processes.

Page 20: Photografting

• Uses UV/visible light to activate precursors for covalent bonding.

Page 21: Self-Assembled Monolayers (SAMs)

• Design features allow SAMs to form covalent bonds, offering smooth and stable surfaces.

Page 22: Amphiphilic Self-Assembled Molecules

• Driving force: Strong reaction between substrates and attachment groups.

Page 23: Non-Covalent Surface Coatings

• Exploration of simpler non-covalent methods.

Page 24: Solution Coatings

• Basic technique involving polymer-dipped substrates, creating non-covalently bound coatings.

Page 25: Langmuir-Blodgett Films (LB Films)

• Amphiphilic molecules applied via a Langmuir trough, achieving uniform coating through pressure adjustments.

Page 26: Surface-Modifying Additives (SMAs)

• SMA Function: Additives that migrate to the surface, driven by lower free energy.

Page 27: SMAs in Polymeric Biomaterials

• Block copolymers that balance compatibility and surface characteristics for desired behavior post-implantation.

Page 28: Layer-by-Layer (LbL) Coatings

• Creates coatings via alternating charge processes.

Page 29: Surface Modifications with No Overcoat

• Techniques modifying surface properties without external coatings.

Page 30: Techniques Overview

• Methods include ion beam implantation, plasma treatment, conversion coatings, bioactive glasses.

Page 31: Ion Beam Implantation

• Utilizes high-energy ions for surface changes to enhance material properties.

Page 32: Conversion Coatings

• Thin oxide layers form on metals to prevent corrosion, improving durability.

Page 33: Bioactive Glasses

• In vivo modification creates active layers enhancing bonding with native bone.

Page 34: Biological Surface Modifications

• Focus on biomolecule attachment techniques influencing cellular interactions.

Page 35: Techniques Overview

• Types of biomolecules and conditions affecting successful attachment.

Page 36: Types of Biomolecules and Applications

• Various biomolecules (enzymes, antibodies, drugs) and their applications in biomedical fields.

Page 37: Covalent Biological Coatings

• Advantages of covalent over non-covalent coatings for stability and reactivity.

Page 38: Post-Fabrication Methods

• Binding agents enable molecule-surface interaction without permanent adhesion.

Page 39: Attachment During Synthesis

• Incorporates biomolecules during the polymerization process for enhanced attachment.

Page 40: Non-Covalent Biological Coatings

• Focus on adsorption principles and stability improvements for biomolecule coatings.

Page 41: Enzyme Immobilization

• Criteria for successful immobilization affecting enzyme applications.

Page 42: Surface Patterning Techniques

• Strategies for altering material surface properties through controlled geometries.

Page 43: Surface Patterning Varieties

• Includes nanoscale and microscale patterns with various fabrication techniques.

Page 44: Direct Writing Techniques

• Uses high-energy beams for precise surface patterns with effective resolution.

Page 45: Microcontact Printing Process

• Steps to create patterns via stamps for controlled surface modification.

Page 46: Microfluidics Implementation

• Technique for specifically treating surfaces with controlled hydrophilicity.