Biomaterials and Young's Modulus Notes

Biomaterials and Young's Modulus

Applications of Biomaterials

• Joint Replacements: Used in hip, knee, and shoulder replacements to restore mobility and reduce pain.
• Hip Replacements
• Heart Valves
• Blood Vessel Prosthesis
• Cochlear Replacements: Used for restoring hearing in individuals with severe hearing loss or deafness.
• Contact Lenses
• Dental Implants: Replace missing teeth and provide structural support for dental prosthetics.
• Skin Repair Devices: Aid in wound healing and skin regeneration, often used for burns or chronic wounds.

Table of Contents

The presentation covers the following topics:

• Young's modulus
• Aim and experiment related to Young's modulus
• Biomaterials classification
• Application of biomaterials
• Biomaterial definition
• Properties of biomaterials

Biomaterial Definition

• Biomaterials are non-viable materials that can be implanted to replace or repair missing tissue.
• Non-viable means they are not capable of living/growing/developing.

Biomaterial Properties

• Biocompatibility: Should not cause harm (e.g., toxicity, inflammation) when implanted.
• Chemical Stability: Should resist corrosion or breakdown in the body’s environment.
• Non-Toxicity: Should not release harmful substances into the body.
• Mechanical Strength: Must match the tissue's needs (e.g., strong for bones, flexible for vessels).
• Degradability: If designed to degrade, should match the tissue healing rate.
• Surface Properties: Should promote cell adhesion and tissue integration.
• Sterilizability: Must withstand sterilization without losing functionality.
• Functionality: Must perform its intended purpose (e.g., support, repair, or deliver drugs).

Biomaterial Classification

• Synthetic
  • Stainless steel
  • Titanium
  • Polymers
• Natural
  • Gelatin
  • Collagen
  • Silk

Application of Biomaterials

• Joint Replacements: Used in hip, knee, and shoulder replacements to restore mobility and reduce pain.
• Dental Implants: Replace missing teeth and provide structural support for dental prosthetics.
• Bone Plates and Cement: Stabilize fractures and support bone healing during orthopedic surgeries.
• Artificial Ligaments and Tendons: Repair or replace damaged connective tissues to restore joint function.
• Surgical Sutures: Stitch wounds or surgical incisions to promote healing.
• Blood Vessel Prosthetics: Used in vascular grafts to repair or replace damaged blood vessels.
• Skin Repair Devices (Artificial Tissue): Aid in wound healing and skin regeneration, often used for burns or chronic wounds.
• Drug Delivery Mechanisms: Controlled release systems for targeted and sustained delivery of medications.
• Ophthalmology: Enhancing vision with corneal implants and lenses
• Cochlear Replacement: Used for restoring hearing in individuals with severe hearing loss or deafness.

Aim

The aim is to determine the Young's modulus of biomaterials equivalent to human bone.

Young's Modulus

• Young's modulus measures the resistance of a material to elastic deformation.
• Elasticity: The ability of an object or material to resume its original shape after being stretched or compressed (force applied).
• A material with a high Young's Modulus is stiff (rigid) and resists deformation (e.g., metals like steel).
• A material with a low Young's Modulus is more flexible and deforms easily under stress (e.g., rubber).
• For any elastic material, the stretching stress is directly proportional to the longitudinal strain.
  • $Stress \propto Strain$
  • $\frac{F}{A} \propto \frac{\Delta L}{L}$
  • $\frac{F}{A} = E (\frac{\Delta L}{L})$
  • Where E is Young's modulus of elasticity (Elastic modulus) measured in Pascals.
• Stress: Force applied per unit area ($\frac{F}{A}$).
• Strain: The resulting deformation relative to the original length ($\frac{\Delta L}{L}$).

Stress-Strain Curve

• The stress-strain curve illustrates the behavior of a material under stress.
• Elastic Region: The region where, once stress is removed, the material returns to its original size/shape.
• Plastic Region: The region where the material is permanently deformed by the stress.
• Yield Strength: The point beyond which the material starts to exhibit plastic behavior.
• Limit of Proportionality: The point up to which stress and strain are linearly related.
• Fracture Point: The point at which the material fractures or breaks.

Bone Composition

• Bone consists of two quite different materials plus water:
  • Bone mineral (60%): The inorganic component (calcium hydroxyapatite), very fragile (brittle).
  • Collagen (40%): Flexible like rubber (ductile).

Material Behavior

• Brittle Material: Fractures suddenly with little or no plastic deformation (e.g., glass).
• Strong Material (Not Ductile): Stretches very little and breaks suddenly (e.g., steel wires).
• Ductile Material: After the elastic region, there is a plastic region where permanent deformation occurs.
• Plastic Material: Very small elastic region.

Experiment Setup

• Bone-equivalent material: acrylic

Young's Modulus Calculation

• Young's developed a law to calculate the elasticity of material:
  • $AY = (\frac{1}{E}) * (\frac{4L^3}{b d^3}) * W$
  • Where $W = m \cdot g$
  • $\frac{AY}{m} = (\frac{1}{E}) * (\frac{4L^3}{b d^3}) * g$
  • $E = (\frac{1}{slope}) * (\frac{4L^3}{b d^3}) * g$
  • Units: Dyne/cm^2
• Given parameters:
  • b (width) = 2.5 cm
  • d (thickness) = 0.1 cm
  • g = 980 cm/sec^2