MECH 500: Bionic Implants and Devices

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MECH 500Bionic Implants and Devices

• Sumitra Rajagopalan
• sumitra.rajagopalan_at_polymtl.ca
• Office Hours
• 5pm 530 pm Mondays
• 4 pm- 5pm Fridays

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Bionic Implants Devices Overview

• Layout of Course
• Evaluation Expectations
• What is the course really about?
• Course Prologue

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Course Layout

• Basic Notions in Medical Devices
• Functional Biomaterials for Bionic Implants
• Design of Soft-Tissue vs. Hard Tissue Implants
• Implant Surfaces and Interfaces
• Bioactive and Bioresponsive Implants
• Functional Tissue Engineering and Bioartificial
  Organs
• Bioelectrodes, Artificial Muscles and
  Neuroprosthetics
• Brain-Machine Interface and Cortical Prosthetics
• Implantable Devices for Minimally-Invasive
  Surgery
• Biosensors, Bioelectronics, Closed-Loop
  Management

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Course Evaluation

• Class Participation 15
• Critical Review of Article(s) OR Case Study 1
  20 (Assigned)
• Third week of September, due early November
• Case Study 2 25 (Assigned or Chosen)
• Third week of October, due at the end of semester
• Take-Home Exam (5 questions) 40
• December 1st, due December 10th

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What you will get out of the course

• A broad, comprehensive overview of the field
• Study the human body from a materials/mechanical
  engineering perspective
• Understand and appreciate differences between
  living and man-made materials and structures
• Custom-design materials and structures to suit
  biological function Biomimicry
• Design appropriate material surface and interface
• Identify optimal control feedback system for
  implant
• Understand and appreciate factors governing
  behaviour in-vivo
• Basic design of biosensors and bioelectronic
  implants including Bio-mems and nems
• Getting medical device to market
• Apply knowledge of human factors engineering to
  extreme enviroments outer space

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So, what is this course really about?
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Medical Devices A Multidisciplinary Enterprise
biology, physiology, biochemistry, immunology
Life Sciences
BIOMATERIALS BIOIMAGING BIONICS BIOMECHANICS BIO
INSTRUMENTATION
electronics, image processing, mechanics,
chemistry, physics, materials, mathematics
Physical Sciences
Engineering
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What is a Medical Device?

• "an instrument, apparatus, implement, machine,
  contrivance, implant, in vitro reagent, or other
  similar or related article, including a component
  part, or accessory which is
• recognized in the official National Formulary, or
  the United States Pharmacopoeia, or any
  supplement to them,
• intended for use in the diagnosis of disease or
  other conditions, or in the cure, mitigation,
  treatment, or prevention of disease, in man or
  other animals, or
• intended to affect the structure or any function
  of the body of man or other animals, and which
  does not achieve any of it's primary intended
  purposes through chemical action within or on the
  body of man or other animals and which is not
  dependent upon being metabolized for the
  achievement of any of its primary intended
  purposes."

www.fda.gov
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Why Bionic ?
1973
1976
1990
2000
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Bionics Inspired by Nature

• Coined by Jack Steeles of the U.S. Air Force in
  1960
• Studying Nature from an Engineering/ Design
  Perspective
• Extracting Structural, Design Paradigms.
• Adopting these paradigms to solve a range of
  engineering problems.
• Other names Biomimicry,Biomimetics

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Bionic Implant Device

• Implant that mimics as far as possible the
  structure AND function of the body part it
  replaces.
• Interacts with the human body in a bidirectional
  fashion
• Examples of Bionic Devices Artificial Heart,
  Artificial Muscle, Cochlear Implant,
  Bioelectrodes, Mechanoactive Cartilage
• Towards seamless integration of implant with
  physiological environment
• Closed-loop system Example of artificial
  pancreas.

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Living vs. Man-Made Reflections
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Living Materials, Structures and Machines

• Multifunctional Materials
• Heirarchical, built through self-assembly
• Ordered, patterned, nano-structured
• Graded properties and functions throughout
  structure
• Seamless integration of materials and structures
  of varying properties
• Control feedback integrated into structure
• Adaptive
• 3Rs renewing, repairing, replicating
• FORM FOLLOWS FUNCTION
• FORM FITS FUNCTION

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FORM FITS FUNCTION Reflection

• Cartilage?
• Muscle?
• Bone?
• Skin?

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Anatomy of an Implant Design Fabrication
Considerations

• Biomaterial
• Bulk Structure
• Interface
• Implant Anchoring
• Sterilisation Method
• Power Issues in Implant Design
• Wireless Monitoring of Implant

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Biomaterials

• Material intended for implanting in human body

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Smart Materials Bridging Materials to Life

• Shape-memory foams
• Shape-memory alloys
• Polyelectolyte Hydrogels
• Piezoelectric Ceramics
• Electroactive Polymers
• Self-healing composites
• Supramolecular Chemistry

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Bionic Devices Behaviour in-vivo

• Biocompatibility/Cytotoxicity
• Ability to function in-vivo with no adverse
  immune reaction
• Biodegradability
• Break-down of biomaterial through action of body
  enzymes into non-toxic byproducts.
• Biostability
• Resistant to break-down in the human body
• Biofunctionality
• Functions as structure intended to replace

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Inflammation Immune System Host Response

• Inflammation occurs through foreign body
  response, movement of implant
• Protein layer formed on implant surface
• Even "inert" materials cause inflammation
• Inflammation reaction can adversely affect both
  patient the functioning of implant
• Engineered biological tissue can cause adverse
  immune reaction
• Still empirical

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Solution? Surface Engineering

• Biorecognisable implant surface
• Designing templates with cell-adhesion molecules
• Micro- and nano-texturing of surface
• Porous Structures Why?
• Drug-eluting surfaces

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Functional Tissue Engineering

• Engineering Living Tissue on Synthetic Scaffolds
• Scaffolds porous, biodegradable, mimic the
  extracellular matrix
• Several parameters at play ?
• Role of Mechanical Engineering Develop
  mathematical models to describe tissue growth on
  scaffolds through these parameters
• Whats the difference between tissue engineering
  and functional tissue engineering?

Boccafoschi, F et al. Biomaterials 26 (2005)
74107417
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Interface with Excitable Tissue Toward
Neuromuscular Prosthetics

• Excitable TissueNerve, Muscle
• Bioelectronic Devices are either stimulate/record
  biosignals (or both)
• Electronic Implant consists of
• Power Source
• Controller
• Stimulator
• Electrode
• Used in a wide range of pathologies spinal cord
  injuries, parkinsons disease, epilepsy, stroke
  etc.
• Nerve-electrode interface remains the weakest
  link
• Study of bioelectric phenomena crucial to
  developing biocompatible electronic implants.

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Notions in Bioelectricity

• Equivalent circuits used to model intefacial/
  bioelectric phenomena
• Impedance Analysis used to calculate parameters
  affecting charge transfer from device-tissue
• Capacitance
• Inductance
• Resistance
• Models derived used to design medical
  instruments, biosensors and other bionic devices

Zhu, F., Leonard,.E Levin,. N Physiol. Meas. 26
(2005) S133S143
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Wrap-up Points to Remember

• Highly multidisciplinary field drawing in on
  chemistry, biology, physiology, mechanics,
  electronics .
• Unlike the man-made world, Nature SEAMLESSLY
  integrates different components and functions
  into a working unit.
• Biological materials vastly differ from man-made
  materials and that has to bet aken into account
  when designing implants
• Bionic Implants emerge ONLY in response to a
  clinical PULL (need)
• Bionic Implants to be designed with Clinical and
  Market Realities in mind.
• Role of Mechanical Engineer Interfacing with
  multiple disciplines, interacting with multiple
  professionals.

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Carbon Nanotube Sheets for use as Artificial
Muscles Discussion Questions

• Differing requirements for robotic vs. prosthetic
  applications
• What are the advantages of carbon nanotubes?
• What are their drawbacks?
• Predict behaviour in-vivo
• Follow-up to this work?