MECH Bionic Implants and Devices

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					      MECH 500:
      Bionic Implants and Devices

Sumitra Rajagopalan

Office Hours:

5pm – 5:30 pm Mondays
4 pm- 5pm Fridays
Bionic Implants & Devices: Overview

•   Layout of Course

•   Evaluation & Expectations

•   What is the course really about?

•   Course Prologue
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

   Getting Medical Device to Market: The Regulatory Environment

   Introducing Bioastronautical Engineering
Course Evaluation
   Class Participation: 15%

   Critical Review of Article(s) OR Case Study #1: 20%
    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
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

   Project ideas for Honour’s, M.Sc/PhD thesis

   Learn the State-of-the-Art in the Field as well as Future Prospects
So, what is this course really
       Medical Devices :A Multidisciplinary Enterprise

                        biology, physiology,
                     biochemistry, immunology
Life Sciences

                    BIOMATERIALS   BIOIMAGING

           chemistry, physics,               electronics, image

          Physical Sciences               Engineering
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

     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."
Why Bionic ?




Bionics: Inspired by Nature
   Coined by Jack Steeles
    of the U.S. Air Force in

   Studying Nature from an
    Engineering/ Design

   Extracting Structural,
    Design Paradigms.

   Adopting these
    paradigms to solve a
    range of engineering

   Other names:
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

   Closed-loop system : Example of artificial pancreas.
Living vs. Man-Made: Reflections
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

   Cartilage?

   Muscle?

   Bone?

   Skin?
Anatomy of an Implant:
Design & Fabrication Considerations

   Biomaterial

   Bulk Structure

   Interface

   Implant Anchoring

   Sterilisation Method

   Power Issues in Implant Design

   Wireless Monitoring of Implant

      Material intended for implanting in
      human body
Smart Materials: Bridging Materials to Life

   Shape-memory foams

   Shape-memory alloys

   Polyelectolyte Hydrogels

   Piezoelectric Ceramics

   Electroactive Polymers

   Self-healing composites

   Supramolecular Chemistry
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
    Inflammation & Immune System: Host Response

   Inflammation occurs through foreign body response, movement of

   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
Solution? Surface Engineering

   Biorecognisable implant surface

   Designing templates with cell-adhesion molecules

   Micro- and nano-texturing of surface

   Porous Structures : Why?

   Drug-eluting surfaces
    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

         What’s the difference between
          tissue engineering and functional
          tissue engineering?

Boccafoschi, F et al. Biomaterials 26 (2005) 7410–7417
             Interface with Excitable Tissue:
           Toward Neuromuscular Prosthetics

   Excitable Tissue:Nerve, 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, parkinson’s disease,
    epilepsy, stroke etc.

   Nerve-electrode interface remains the weakest link

   Study of bioelectric phenomena crucial to developing biocompatible electronic
      Notions in Bioelectricity
          Equivalent circuits used to
           model intefacial/ bioelectric

          Impedance Analysis used to
           calculate parameters affecting
           charge transfer from device-
                Capacitance
                Inductance
                Resistance

          Models derived used to design
           medical instruments,
           biosensors and other bionic

Zhu, F., Leonard,.E Levin,. N Physiol. Meas. 26 (2005) S133–S143
    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.
     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?

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