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Precise Materials Selection in Medical
Device Design: Streamlining the materials selection process &
getting it right from the start
Kristen Roenigk Granta Design
Overview
Introduction
• How important our materials
Designing with materials
• Harnessing all available knowledge
• Optimising the initial material selection process
• Looking towards the future
How Important are Materials?
LAST YEAR, OVER 437 MILLION DEVICES WERE RECALLED
FOR FEAR THEY MIGHT KILL OR PERMANENTLY HARM
PATIENTS.
A major product recall is a monumental event in the life of a
medical device company.
Recall Costs
Costs include:
• product removal, service, or correction
• product replacement
• loss of stock
• loss of future sales
• Loss of reputation
• litigation
Recent Examples
Boston Scientific quoting $8m in lost sales
due to a recall of catheters
Johnson & Johnson citing costs for a hip
recall program as contributing to a 12%
decline in quarterly profitability
1 in 8 patients who received a DePuy ASR
Hip replacement will require revision
surgery.
Materials in Medical Device Development
Concept
Definition and Planning
Design and Development
Verification and Validation
Commercialization
• Technology feasibility
• Competitor analysis
• Materials selection
• Understanding and performing
additional testing needs
• Use of CAD, FEA, CAE…
• Regulatory requirements
• Verification of design inputs
• Manufacturing scale up
• Supplier/formulation changes
Materials in Medical Device Development
Concept
Definition and Planning
Design and Development
Verification and Validation
Commercialization
• Technology feasibility
• Competitor analysis
• Materials selection
----------------------------------------------------------
• Understanding and performing
additional testing needs
• Use of CAD, FEA, CAE…
• Regulatory requirements
• Verification of design inputs
• Manufacturing scale up
• Supplier/formulation changes
CRITICAL POINT
Materials in Medical Device Development
Concept
Definition and Planning
Design and Development
Verification and Validation
Commercialization
• Technology feasibility
• Competitor analysis
• Materials selection
----------------------------------------------------------
• Understanding and performing
additional testing needs
• Use of CAD, FEA, CAE…
• Regulatory requirements
• Verification of design inputs
• Manufacturing scale up
• Supplier/formulation changes
Beyond material selection:
• Design change preferable to change of
material
• Inability to fit design to material results
in extensive project delays
• Success of product depends on quality
of material selection
Approaches to choosing materials
Traditional Methods
• Choose a material that was used before
• Choose a familiar material
• Ask a colleague
• Ask the manufacture
• Bring in a consultant
• Search the web
Approaches to choosing materials
Advantages
• Draws on past experience of engineers, consultants etc.
• Fast process
Challenges
• Consideration of technology advances
• Utilizing additional company expertise
• Understanding material performance in a given application
• Auditability and traceability of process
From using materials to designing with materials
Main elements:
1. Harnessing the power of all available knowledge
2. Optimising the initial material selection process
3. Looking towards the future
From using materials to designing with materials
Main elements:
1. Harnessing the power of all available knowledge
2. Optimising the initial material selection process
3. Looking towards the future
Materials Knowledge in Typical Design Process
New
Concept
Material selection: Designer selects
materials
Material research: mechanical chemical
biocompatibility environmental
Prototypes and tooling
Clinical trials Raw materials:
Procurement Inspection
Device manufacture
Commercial use
Post launch: Customer feedback Changed standards Supplier changes
Formulation changes
Material
KNOWLEDGE INVESTMENT
Mechanical
properties
Properties of
biological
tissues
Biocompatibility
Predicate
devices
Materials Knowledge in Typical Design Process
Another
New
Concept
Material selection: Designer selects
materials
Material
KNOWLEDGE INVESTMENT
Takes too much time to find
Cannot specifically search for materials information
Different teams unaware of what data exists
Managing the materials lifecycle
Corporate
Materials
Resource
Project 1 Reference data
Project 2
Search Browse Report Import from test
Export to CAE Find substitutes Minimum cost design
Analyze test data
Etc… Tools
One place to go for materials information
Controlled
access
Specialist Reference Sources
Example: ASM Medical Materials Database
Combines:
• Scientific journals
• Handbooks/textbooks
• Supplier datasheets
• FDA device approvals
• Expert knowledge
Covers:
• Engineering properties
AND biological response
AND coating and drug compatibility information
• Application information –
where materials are used in predicate orthopaedic and
cardiovascular devices
Best practice management
Materials resource should:
• Controlled access – the right people see the right data
• Handle complexities of material data
e.g. functional data
• Highlight quality of data
• Enable maintenance of information traceability
Automated tools preferable
• Employ version control for change management
1: Complete material information lifecycle
Material research: mechanical chemical
biocompatibility environmental
Prototypes and tooling
Clinical trials
Raw materials: Procurement Inspection
Device manufacture
Commercial use
Post launch: Customer feedback Changed standards Supplier changes
Formulation changes
Material
KNOWLEDGE INVESTMENT
Material selection: Designer selects
materials
Another
New
Concept
2: Share across the company
Material
KNOWLEDGE INVESTMENT
Division A
Material
KNOWLEDGE INVESTMENT
Division B
2: Share across the company
Material
KNOWLEDGE INVESTMENT
Division A
Material
KNOWLEDGE INVESTMENT
Division B
Material
KNOWLEDGE INVESTMENT
Material
KNOWLEDGE INVESTMENT
Material
KNOWLEDGE INVESTMENT
Material
KNOWLEDGE INVESTMENT
Division C
Division D Division E Division F
From using materials to designing with materials
Main elements:
1. Harnessing the power of all available knowledge
2. Optimising the initial material selection process
3. Looking towards the future
Approaches to choosing materials
Ideal: Ashby Methodology
All materials
Breakdown design requirements into:
Function – What does the component do?
Constraints – What essential conditions must be met?
Objectives – What is to be maximized or minimized?
Screen on constraints - ‘Go’ / ‘no-go’ criteria (usually many)
Rank on objectives - Ordering of materials that ‘go’
Top candidate materials DESIGN WITH MATERIALS
Exhaustive
Auditable
Repeatable
}
Ranking – performance indices
FUNCTION
Tie
Beam
Shaft
Column
Mechanical,
Thermal,
Electrical...
CONSTRAINTS
Stiffness
specified
Strength
specified
Fatigue limit
Geometry
specified
Minimum cost
Minimum
weight
Minimum
volume
Minimum
eco- impact
OBJECTIVE
Minimize this!
INDEX
y
M
Function
Constraint
Objective
Each combination
has a
material index
Material performance in different applications
Tie in tension
Panel in bending
Permeability (O2) per unit of stiffnessGas/vapor barrier in bending Fixed: area Free: thickness
0.01 0.1 1 10 100 1000 10000 100000
Cost
per
unit o
f st
iffn
ess
Panel in
bendin
g
Fix
ed:
length
, w
idth
F
ree:
thic
kness
1000
10000
100000
PS (heat resistant)PVC (rigid, molding and extrusion)
PET (unfilled, amorphous)
Acrylonitrile copolymer (extrusion)
EVOH (unfilled)
PVDC (copolymer, barrier film resin, unplasticized)
Polyester liquid crystal (unfilled)
Example of resulting ‘Ashby chart’ L
ow
er
Co
st
Lower Permeability
Case Study: Electrosurgical Forceps
Component:
• Handle of minimally-invasive
electrosurgical forceps
Constraints:
• Biocompatibility USP class VI or ISO 10993
• Sterilizability (steam autoclave) Good or Excellent
• Mechanical Stiffness and Strength in bending
• Mechanical toughness Impact Strength >7 kJ/m^2
• Electrical Insulator
• Dimensional stability Water absorption @ 24hr < 0.5%
• Processing 3D complex shape
Objectives
1. Minimize cost for a specified stiffness
2. Minimize volume for a specified stiffness
Composites Technology, Dec 2003
E
cCost m
EVolume
1
Constraints
Ashby methodology
Comparison Table
Polyarylamide
(50% glass fiber)
PPS
(40% glass fiber)
SPS
(30% glass fiber)
PEEK
(30% glass fiber)
Computed Properties
Cost per unit of stiffness 2520 - 3180 4910 - 6090 2440 - 2990 35900 - 41900
Volume per unit of stiffness 0.225 - 0.246 0.259 - 0.292 0.296 - 0.355 0.302 - 0.34
General properties
Density (kg/m^3) 1630 - 1660 1600 - 1670 1270 - 1290 1490 - 1540
Price (USD/kg) 6.56 - 8.14 11.1 - 13.3 6.2 - 6.82 76.3 - 83.9
Composition overview
Base Polymer Polymer Polymer Polymer
Polymer class Thermoplastic : semi-
crystalline
Thermoplastic : semi-
crystalline
Thermoplastic : semi-
crystalline
Thermoplastic : semi-
crystalline
Polymer type PA-MXD6 PPS PS-SY PEEK
Polymer type full name Polyarylamide Polyphenylene sulfide Polystyrene, syndiotactic Polyetheretherketone
% filler (by weight) (%) 46 - 50 40 30 30
Filler type Glass fiber Glass fiber Glass fiber Glass fiber
Bio-data
Sterilizability (ethylene oxide) Good Excellent Good Excellent
Sterilizability (radiation) Good Excellent Good Excellent
Sterilizability (steam autoclave) Good Excellent Good Excellent
Mechanical properties
Young's modulus (GPa) 17.8 - 22.2 7.58 - 14.5 6.9 - 10.3 8.62 - 11
Compressive modulus (GPa) 19 - 21 7.58 - 14.5 6.9 - 10.3 8.62 - 11
Flexural modulus (GPa) 16.5 - 19.8 11.7 - 14.9 7.93 - 11.4 8.66 - 11
Shear modulus (GPa) 7.31 - 7.68 2.81 - 5.37 2.52 - 3.81 3.18 - 4.06
Bulk modulus (GPa) 19.1 - 21.1 11.4 - 12 7.94 - 12.6 10.9 - 11.5
Poisson's ratio 0.329 - 0.334 0.34 - 0.364 0.353 - 0.367 0.39 - 0.41
Impact properties
Impact strength, notched 23 °C (kJ/m^2) 6.19 - 12 8.14 - 10.8 6.37 - 14.3 9.09 - 11
From using materials to designing with materials
Main elements:
1. Harnessing the power of all available knowledge
2. Optimising the initial material selection process
3. Looking towards the future
Proactive companies
• Cost & competitive advantage
• Branding—corporate image
Legislation & regulation
Customer expectation
Materials scarcity
Drivers for eco design
REACH
An effective response to eco drivers
Design Brief
Conceptual Design
Embodiment Design
Detailed Design
Manufacture
Use
Incre
asin
g c
ost Eco Design
tools Quick, iterative
Granta:
- Eco & restricted substance tools
- Integrated with M&P selection
Conventional response:
- LCA
- Compliance reporting
Detailed, time-consuming
Did information on restricted
substances and the regulations
that impact them
Assess business risk
• Where are restricted substances?
Design-out restricted substances
• Select & substitute materials to
avoid problems
Augment your business systems
• Apply within CAD or PLM
Restricted substances
Legislation &
Standards
REACH
RoHS
Dodd Frank
Summary
Materials selection is critical in medical device development
Lack of consideration leads to increased design iterations and
extended project times
Increasing time to market and costs to the company
Summary
Need to:
Harness the power of all available knowledge
• Corporate materials knowledge resource
• Specialist reference and internal knowledge
Optimize the initial material selection process
• Employ rational methodology (Ashby)
Look towards the future
• Eco Design
• Restricted Substances
Thank You!
Any Questions?
