Gregory Washington, Ph.D.Farzad Ahmadkhanlou, Ph.D., P.E.

GLOBEX 20191

An Introduction to Smart Materials and Adaptive Systems

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What are smart materials?• The technology paradigm states that a smart material is a structure that

involves the integration of actuators, sensors, and controls with a material or structural component. This definition describes the components but it does not state any system goals or objectives.

• The science paradigm states that a smart structure is a structural system with intelligence and life features integrated in the macrostructure and quite possibly the microstructure of the system to meet stated objectives and to provide adaptive functionality. It does not define the type of materials or state that actuators, sensors, or controls are used.

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Smart Materials

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Why use Smart Materials?• These materials have the following qualities

• No moving parts, High reliability• Low power requirements• Materials provide new, synergistic capabilities that are presently not possible

• While many of these technologies are mature, they represent an area of innovation for many

• Presently about 175 patents/year are issued in piezoceramics alone.• $4 Billion dollar market (75% - Electro-ceramics, 10% -Shape Memory Materials,

10% - Magnetostrictive materials, 5% MR- Fluids)• Students get enthusiastic about new and exciting avenues of research. These

materials let your imagination run wild

Prevailing Concepts• What is in a NAME ?

• Smart Structures• Intelligent Structures• Metamorphic Structures• Adaptive Structures• Sensory Structures• Sensory Materials• Sensory Systems• Energy Transfer Materials

Lightest Known Material

Cephalopod Inspired Materials

A new materials paradigm

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Prevailing Concepts - BiomimeticsSystem ComponentsLoad-bearing structurePropulsionSurvivability featuresPower (fuel)Payload

Natures SystemsFunctions evolved in unisonComponents are multifunctional

Synthetic SystemsFunctions are isolated

Components are single function

Minnesota Wood Beetle

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Prevailing Concepts - Biomimetics 2.

• A hetero-nanostructured material

• Chitin fiber (3nm x 180nm)• Protein matrix

• pH control• Water content control• Modulus control

• Pore Canals• Multi Layered arrangement

• Stiffer outer/softer inner

• Design Problems solved by nature

• Fiber orientation/placement• Self Repair, growth• Temperature control• Canal distribution without

weakening the structure

Minnesota Wood Beetle

Cuticle

Prevailing Concepts - Biomimetics 3.• Skeleton-Composite Materials• Muscles:

• Piezoelectrics, ElectroactivePolymers -Fast Twitch

• Shape Memory Alloys-Slow twitch muscles

• Control-Artificial Neural Networks

• Sensory - Optical Fibers• Immune System ?

Biomimetics is based on the premise that nature has solved an optimization problem

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Can Material Inspire Us?

• Space age materials excite students!

Smart fluid developed at the Michigan Tech Terminator 2 - Hollywood

Types of Smart Materials

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Type of SMART Material

Input Output

Piezoelectric Deformation Potential Difference

Electrostrictive Potential Difference Deformation

Magnetostrictive Magnetic Field Deformation

Thermoelectric Temperature Potential Difference

Shape Memory Alloys Temperature Deformation

Photochromic Radiation Color Change

Thermochromics Temperature Color Change

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Smart Materials - Introduction

• In general all active materials are transducers. This means that they convert energy from one form to another.

Output /Input

ChargeCurrent Mag. Strain Temp. Light

Elec. Field PermittivityConductivity.

Elect-MagEffect

Converse PiezoEffect

Elec.CaloricEffect

Elec. OpticEffect

Mag. Field Mag-electEffect

Permeability

Magneto-striction

Mag.Caloriceffect

Mag. OpticEffect

Stress PiezoelectricEffect

Piezomagnetic

EffectCompliance

Photo-ElasticEffect

Heat PyroelectricEffect - Thermal

ExpansionSpecific

Heat -

Light Photovol taicEffect - Photostriction - Refractive

Index

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Smart Materials as Sensors

• Typical sensors consist of strain gauges, accelerometers, fiber optics, piezoelectric films and piezoceramics. Sensors convert strain or displacement (or their time derivatives) into electric field. Key factors are:

• Sensitivity to strain or displacement• Bandwidth,• Size. • Other less important factors include temperature sensitivity, linearity, Hysteresis,

electromagnetic compatibility, embeddibility, and needed associated electronics

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Smart Material Sensors

• The sensitivity for resistor gauge is 30 volts per strain, for asemiconductor gauge is 103 volts per strain, and forpiezoelectric and piezoceramic gauges is 104 volts perstrain. The sensitivity for fiber optics sensors is defineddifferently, and is about 106 degree per strain.

Sensor Resistance gauge 10V excitation

Semiconductor gauge

10V excitation

Fiber Optics 0.04"

interferometer gauge length

Piezofilm .001"

thickness

Piezoceramics .001"

Thickness

Sensitivity 30 V/ε 1000 V/ε 106 deg/ε 105 V/ε 2x104 V/ε Localization

(Inches) 0.008 0.03 0.04 < 0.04 < 0.04

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Smart Material Actuators

• Microstrain can be defined as:

Actuators PZT G-1195 PZT-5H PVDF PMN Terfenol DZ Nitinol

Actuation Mechanism

Piezo-ceramic

Piezo-ceramic Piezofilm Electro-

strictive Magneto strictive

Shape Memory

Alloy Free Strain

Λmax, µ strain 1000 1000 700 1000 2000 20000

Modulus E (106) psi 9 10 0.3 17 7

4 for (martensite)

13 for (Austenite)

Band Width High High High High Moderate Low

εmax for 10=

c

b

tt

Aluminum Beam

400 350 10 500 580 8500

Strain- Voltage Linearity Non-linear Non-Linear Non-Linear Non Linear Non Linear Non Linear

µstrain = strain *106 Ex. 0.00005 strain = 50 µstrain

Types of Smart Materials

MR Fluids

Piezoelectric Materials Shape Memory Alloys

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Types of Smart Materials

Magnetostrictive Materials Electroactive Polymers

Piezoelectric Materials• Piezoelectricity describes the phenomenon of generating an electric

charge in a material when its subjected to a mechanical stress (direct effect) and conversely generating a mechanical strain in response to an applied electric field.

• Discovered in 1880 by Pierre and Jacques Curie• Types

• Piezoceramic elements• Lead Zirconate Titanate (PZT)• Barium Titanate , Cadmium Sulfide

• Piezoelectric Polymer• PVDF • PVC

• Applications: Smart Sensors for Side Impact Diagnostics, Wiper activation Sensors, Ultrasonic motors, Motion/Force Sensing, Yaw rate sensors, Platform Stabilization Sensors, sonar array arrays for collision avoidance

Active Materials

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Piezoelectrically Actuated Swimming Vehicle

• Designed and built by Undergrad Students

Actuators

Drive Electronics

Propeller

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Leading and Trailing edge control Surfaces

Smart Wing Program: Northrup Grumman

Smart Wing AircraftFlexible Wing

Unmanned Aerial Vehicles

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Piezoelectric Miniature Actuator

• Small Piezoceramic Inchworm actuator• Employs MEMS teeth

UCLA Active Materials research Lab

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Other actuated systems

Actuator for Smart Eyeglasses

Smart Shoe concept

Uchino - PSU Paradiso - MIT

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Large Deflection Actuators

Actuator Actuated system

• Deflections of up to 1” have been achieved from a 4” long structure

FACE International

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Yaw Rate Sensors for Chassis Control• Currently in production for GM’s StabiliTRAK integrated

control system (offered on certain Cadillac Models)• Consists of a micro-machined double-ended quartz tuning

fork that senses the yaw rate via the Coriolis effect.

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Active Vibration Control

• Piezoceramic motions counter the motion of a vibrating structure

• Can be used reduce noise as well

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Magneto/Electro-Rheological Fluids

• Experience reversible changes in rheological properties (apparent viscosity, plasticity, and elasticity) when subjected to a electric field.

• The fluid contains micron sized dielectric particles suspended in a nonconductive base medium

• With recent advances in magnetorheological systems high force systems are now achievable

• Uses: Active Damping Comfort systems -Delphi Magnaride system, Active Suspension, Active Clutch Mechanisms, Position and Velocity Control, Force-Feedback and Tactile Feel

MR Fluid Applications

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Magneto-Rheological Systems

• Unstimulated Fluid has the consistency of a thin milkshake

• Stimulated fluid has the consistency of Ice Cream

Lord Corporation

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MR Fluid - Applications

• Driver is able to change the feel and comfort of ride quality

Cadillac 2002 Seville MR Damper used in Cadillac

Lord Corporation

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Other MR Fluid Applications

• Damper allows patient to adapt to various gait conditionsLord Corporation

MR Fluid Applications – Haptic Glove

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Electroactive Polymers

• Name given to a class of polymers that have controllable properties triggered by a variety of stimulators (electrical, magnetic, photonic, chemical)

• First discovery: Roentgen in 1880• Two major types: Electronic and Ionic• Electronic polymers (generally need high fields)

• (piezoceramic, electrostrictive, electrostatic)• Ionic polymers (generally need to be wet)

• (gels, polymer metal composites, conductive polymers)

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Electroactive Polymers

• Nature inspires Man• The goal is to use these polymers in the development of artificial muscles

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Electroactive Polymer Applications

• Hand moves through the use of Ionic Polymer Metal Composites

• Two major types: Perfluorosulfonate (Nafion) and Perfluorocarboxylate(Flemion)

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Electroactive Polymer Applications 2.

• Artificial heart assisted by active polymersUniversity of New Mexico - Artificial Muscle Research Institute

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Polyvinylidene Fluoride• Polyvinylidene fluoride (PVDF), also abbreviated PVF2 is a polymer with

the strongest known piezoelectric properties of all polymers. The film iscommonly used in two states: one called the alpha phase and the othercalled the beta phase.

• In the alpha phase, PVDF is not polarized and is used as a commonelectrical dielectric. In the beta phase the material is polarized and has astrong piezoelectric effect.

• Attributes• High Compliance, Easily Customizable• Less force transduction than PZT, higher sensitivity• High Voltage Output (g constant is 10-20x higher than piezoceramics), Wide

Bandwidth (0.01 - 109 Hz)• Pyro-electric (DT of 1 °C gives 1.5 Volt open circuit)• Similar Performance to strain gages (with no conditioning needed)

Shape Memory Alloys

• A object in its low temperature (martensitic) state when plastically deformed with all of the external stresses removed, will regain its original (memory) shape when heated. Up to 8% extensional prestrain can be 100% recovered

• The effect was discovered in 1932. In 1962 researchers at the Naval Ordinance Labs discovered that Nickel-Titanium alloys exhibit this effect significantly

• Types• gold cadmium• Brass• Nitinol

• Superior strain 3-25 times higher than piezoelectrics• Increase in Young’s modulus of between 3 to 5 times

• Other material properties change with the state change• Extremely Low bandwidth materials

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Shape Memory Alloys• Shape memory alloys possess the ability to undergo significant shape deformation

at low temperatures and retain this deformation until they are heated. When they are heated, they remarkably return to their original shape.

• The effect was first discovered in samples of gold cadmium alloys in 1932 and later in copper-zinc (brass) alloys in 1938. In 1962 researchers at the Naval Ordinance Labs discovered that Nickel-Titanium alloys exhibit this effect significantly.

• Ni-Ti alloys (Nitinol) have received a significant amount of press lately because of the high recoverable strains (up to 10%) associated with this material. There are at least 18 other alloys however that exhibit this effect.

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Shape Memory Alloys• SMA’s are thermal

mechanical devices• When the structure is

heated a shape change occurs

• When the structure cools it must deformed to exhibit the behavior SMA Demonstration

MR Fluid Video

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Shape Memory Alloy - Applications

• Alloys that change shape when heated

• Small 6-legged walking robot, propelled by shape memory alloys

• Alloys are heated causing a deformation

• They return to their original shape when they are cooled.

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SMA Applications

SMA Bone Plate

Bone Plate in Jaw

SMA Stents

Microbubble Actuator

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SMA Applications - Con’t

• When the SMA wire actuator structure is heated, the system deforms• The structure is a 27” wing span• Deflections >1.5” in H20 was recorded

Undeformed Deformed

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Other SMA Applications

• Smart materials are all around us!

Special (solderless joints)

Flexible Toothbrushes

Cell Phone antennas

Thermochromic Materials

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Smart Gels

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Smart Materials – Medical Applications

Electrochromic Materials

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Transparent and looks like ordinary glass

Application of small voltage turns it opaque

(blueish and dark)

What do you have to know?

• The Physics of how they work• The mathematics of applying them• How to think creatively about what can be done and

what can’t• Actually everything can be done, it just may require an

adjustment of thought.

Thank You!

Obrigado!

¡Muchas Gracias!

感謝!

Merci Bien!

Asante Sana!

СПАСИВО!

Vielen Dank!

Grazie!

谢谢!

Tak!