Contact Lens

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INTRODUCTION TO BIOMATERIALS BMEN 343 Prof.
Melissa Grunlan
Contact Lens
bone plates
knee hip replacement
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What are MATERIALS?

1. Solids
2. Liquids
3. Gases
4. All of the above

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What are BIOMATERIALS?
materials that can function as a

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CLASSES OF BIOMATERIALS
Metals Ceramics Polymers
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What is a Metal?

• Which elements are metallic?

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What is an alloy?

• Examples in biomaterials
• - Titanium alloy (Ti-6Al-4V)
• 90 Ti, 6 Al, 4 V low amounts of H, Fe, N,
  C
• femoral stem
• - Stainless steel 316L
• 63 Fe, 18 Cr, 13 Ni low amounts of N, Mn,
  Mo, P, Si, S, and C
• femoral head (occasionally)

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Metals and Alloy Devices
Advantages
Disadvantages
Examples Joint replacement Dental root
implants Orthopedic fixation bone plates
Knee replacement
Shoulder replacement
Dental implant (root)
Bone plate
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What is a Ceramic?

• Example in biomaterials
• Aluminum Oxide/ Alumina (Al2O3)
• Femoral ball liner (occasionally)
• Acetabular cup liner (occasionally)

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Ceramic Devices
Advantages
Disadvantages
(these terms will be defined later)
Examples Dental implant (looks like
bone/tooth) Some joint replacement articulating
surfaces Bone cement filler to encourage bone
in-growth (older patients)
Dental implant (root)
Elbow joint
Hip joint
Cemented hip joint
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What is a Polymer?

• Example in biomaterials
• UHMWPE
• -CH2-CH2-
• MW 2-3 million g/mols (n 107,143)
• acetabular cup liner (most common)

n
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Polymer Devices
Disadvantages
Advantages
Examples Some joint replacement articulating
surfaces Spinal cages Biodegradable bone plates
for low load regions Biodegradable sutures
Bone plates
Hip joint
Spinal cage for spine fusion
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BIOMATERIALS CAN BE USED TO FORM
Exoprothesis Endoprothesis -
Artificial Liver
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How do biomaterials fit into biomedical
engineering?
idea
FACILITATOR
ACTION

• Identify a need
• Treat disease
• Replace organ
• Cosmetic

Physician Engineer/Scientist
implementation
Engineer Physician
Device Design
Biomaterials Selection Biomaterials
Development Biomaterials Testing
Engineer Scientist
patient
Fabrication, sterilization, device testing,
regulatory, clinical use
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1. Identify a Need Replacement of Deteriorated
Hip Joint
Osteoarthritis loss of cartilage
The hip joint is the largest load-bearing joint.
A hip joint is lined with articular cartilage a
layer of tissue that provides low-friction and
shock-absorbing properties. Arthritis and injury
can damage this protective layer of cartilage,
causing extreme pain for a patient performing
even simple activities.
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2. Design Device Total Hip Replacement
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3. Biomaterial Selection
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• gt 250,00 per year in USA
• By 2030, gt 750,000 per year in USA
• Average age 66 years
• 57 women

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• Modern design Late 1960s, John Charnly
• Success rate
• After 10 years 90 function well
• After 20 years 80 function well
• After 30 years 50 function well

Failure is related to the limitations of the
current biomaterials used for the components (as
well as design issues).
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Useful Definitions

• Biocompatible
• the ability of a material _______________________
  __
• ___________________________________________
• in a specific application
• Biomaterials must be biocompatible, but the
  _______ or _________ of biocompatibility
  varies for biocompatible materials.
• _____________________determines
  biocompatibility.

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Useful Definitions
Foreign Body Reaction host response to
biomaterial
some biomaterial
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Useful Definitions
Bioinert Bioactive - For example, bioactive
glasses stimulate bone tissue growth
Cement contains bioactive glass
Cemented hip joint
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Useful Definitions
Biodegradable Undergoes degradation in the
body - Degradation ___________________________
__ - Degradation products are harmless and can
be secreted naturally
water
Lactic acid
PLLA bone plates
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BMEN 343 Introduction to Biomaterials
Fundamental Material Science Engineering
Concepts Introduction to the structure-property
relationships of engineering materials.
Structure Atomic structure and bonding crystal
structures imperfections in solids diffusion
structures of metals, ceramics and
polymers. Mechanical Properties The mechanical
properties of metals, ceramics, and polymers
(including processing and failure) and their
relationship to material structure.
Atomic Structure
Crystal Structure
Dislocations in Ti alloy
Modulus, strength, failure
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Mechanical Properties Why is important to study
for all biomaterials?
Determines how well it will work (or not work)
for a given device. One major factor is the
modulus of the material.
metal
polymer
polymer
Toe implant
______________
hydrogel
____________
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What is a modulus?
Material E (GPa)
Silicone Elastomer (Rubber) 0.002
Polyethylene (PE) 0.69
Poly(methyl methacrylate) (PMMA) 2.2-3.2
Cortical Bone 17- 24
Cancellous Bone 0.1 4.5
Glass 73
Gold 77
Ti-6Al-4V 114
Stainless Steel 316L 190
Tantalum 190
Haynes-Stellite 21 (Cast Co-Cr-Mo) 210
Aluminum oxide 380
Diamond 700-1200
What is a GPa? 1GPa 103 MPa 109 N/m2
____________
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Mechanical Properties of Biomaterials

• Must not _______________________________under
  physiological loads
• __________________________________________(and
  thus device success).
• e.g. stress-shielding and restenosis
• Load depends on device
• Modulus (E) depends on material
  structure/composition/-defects/impurities

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Mechanical Properties of Biomaterials

• CASE 1 Modulus of device gt Modulus of tissue

higher modulus of the bone plate vs. the
surrounding bone tissue leads to
___________________? bone loss ? implant
loosening ? possible fracture
Stainless Steel 316L (bone plate) E 193
GPa Cortical Bone 17-24 GPa
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Mechanical Properties of Biomaterials

• CASE 2 Modulus of device lt Modulus of tissue

Can only be used in low load-bearing
applications (e.g. wrist not femoral fractures)
PLLA (bone plate) E 2.7 GPa Cortical Bone E
17-24 GPa
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Mechanical Properties of Biomaterials

• CASE 1 Modulus of device gt Modulus of tissue

• __________________ re-blocking of artery due to
  the formation of neointima thick smooth muscle
  tissue inside lumen

Stainless Steel 316L (Stent) E 193 GPa Artery
E 0.1 MPa
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Mechanical Properties of Biomaterials

• Biodegradable Polymer Stents
• Present long enough for vessel to
• re-model and then it dissolves
• Can be drug-loaded
• Minimize restenosis
• Disadvantage ___________ (collapse)

PLLA (Stent) E 2.7 GPa Artery E 0.1 MPa
LASER LACE This biodegradable polymer stent
was cut by an ultrafast laser.
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Some other devices.
KNEE REPLACEMENT
The healthy human knee joint is aslo lined with
articular cartilage. Arthritis and injury can
similarly damage this protective layer of
cartilage causing extreme pain.
wear
http//tc.engr.wisc.edu/UER/uer01/author1/content.
html
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POLYMERS IN OPHTHALMICS

• Intraocular Lens replace opaque crystalline
  lens (cataract) of the eye

Inflexible IOL Tg 105 ?C ________ Larger
incision needed
Foldable IOL Tg (PDMS) -125 ?C
__________ Smaller incision
PDMS PMMA
Silicone Acrylates
PMMA
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POLYMERS IN OPHTHALMICS
2. Soft Contact Lenses placed on cornea to
correct vision
Hydrogels
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Some Allotropes of Carbon
graphite
diamond
C60 Buckyball
Pyrolytic carbon (PyC)
carbon nanotube
Montreals 1067 Expo American pavilion at night
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FYI
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Electron Energy States
Electrons...
have discrete or quantized energy states
(permitted energy values) tend to occupy
lowest available energy state.
Adapted from Fig. 2.4, Callister 7e.
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The Periodic Table
Electropositive elements Readily give up
electrons to become ions.
Electronegative elements Readily acquire
electrons to become - ions.
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