Artificial Muscle

Kori Brabham

Misti Marr

Andy Smith

Paul Lee

Natural vs. Artificial Muscle

What does a natural muscle do? It is a contractile organ. It consists of fibers which “actuate” force and

motion in response to nervous stimulation.

How does it work? Muscles contract by the chemo-mechanical action

of the proteins actin and myosin. Joints of the body are arrayed such that they

comprise muscles which oppose each other.

Natural vs. Artificial Muscle

How can we develop replacements for the natural muscle? Develop biomimetic actuators. Emphasis on implantable technologies (not on the

the forefront now).

What do we have to work with? Electrical/pneumatic servos (robotic limbs, late

1940’s-present). New materials.

Synthetic polymers Carbon

What constitutes a muscle?

Any system or combination of sub-systems can be considered a “muscle”: hydraulic/pneumatic cylinder. electromagnetic servo. biological muscle tissue.

In short, anything which accomplishes actuation under the command of a stimulus.

Muscles primarily exert energy (ATP) to bring about: motion, acceleration (v/ t or 2x/ t2). force application (F=m.a).

Muscles Revisited

Muscle cells are highly specialized for contraction.ONLY contract and relaxAbduction and adduction

Actin and myosin vary in amounts and configuration, depending on cell function.

Three types

Skeletal – voluntary and striated

Cardiac – involuntary, striated, and branched

Smooth – involuntary and unstriated

The Design of Natural Muscle

Muscles are simply transducersThey change the chemo-electric signal

from nerves to mechanical energy.

Artificial muscles should be similar in resilience and in the ability to produce large actuation strains

http://www.unm.edu/~amri/protect/

Brief Timeline

1619 - Descartes postulated that sensory impulses activated muscle (reflection)

1780 - Galvani noticed frog muscles would contract with electrical apparatus

Brief Timeline (cont’d)

1968 – Rubber artificial muscle Involved several

thread running along a longitudinal axis

Compressed air is injected

Brief Timeline (cont’d)

1968 - Model Postural Control A biped walking

machine is required to maintain it’s balance while standing and walking

Artificial Muscle—An Overview

Many types of artificial “muscle”.McKibbin muscle actuators Inflatable air tubes, delivering large force at a low

frequency.

PAN-chemically stimulated by pH change.Electrically Stimulated “Tissues” IPMC Solenoids (not presented) Piezo-active polymers and ceramics (not

presented)

A Review of Current Technology

The McKibben Artificial Muscle

History

First developed in the 1950's by American physician Joseph L. McKibben originally intended to actuate artificial limbs for amputees

More recently was commercialized in the 1980's by Bridgestone Rubber Company of Japan patented and called “Rubbertuator”

Presently the Shadow Robot Group of England manufactures these actuators for robotic applications

How it’s made

Consists of an internal bladder

Bladder is covered by a braided mesh shell

Attached at either end to tendon-like structures

How it works

Internal bladder is pressurizedBladder expands in a balloon-like manner against the braided shellShell constrains the expansion to maintain a cylindrical shapeAs the volume of the bladder increases due to the increase in pressure, the actuator shortens and produces tension

High force to weight ratio

Lightweight

Low Cost

Smooth

Advantages of the McKibben Artificial Muscle

Size availability

Flexible

Powerful

Damped

Effective

Comparison to biological muscle

Force-length properties are reasonably close

Force-velocity properties are not close a device called a hydraulic damper that operates

in parallel with the McKibben muscles has been created

McKibben muscles are attached to a spring-like device that simulates the tendon properties and energy storage of a real muscle

Ionic Polymer-Metal Composite

How it’s made

Composed of a perfluorinated ion exchange membrane

Consist of a polymer matrix that is coated on the outer surface with platinum in most cases (silver and copper have also been used) coating aids in the distribution of the voltage over

surface

Made into sheets that can be cut into different shapes and sizes as needed

How it worksUses electricity (electrodes, conductors, etc.) to operateA circuit is connected to surface to produce voltage difference, causing bending

Strips can bend and flap dramatically which allows movement

Advantages of IPMCLight

Compact

Driven by low power

and low voltage

Large strain capability

Comparison to biological muscle

High fracture tolerance

Large actuation strain

Inherent vibration damping

Responds to electricity with elasticity and responsiveness similar to those shown to biological muscle

Nanotube Artificial Muscle

Invented by Max Plank Institute, produced by AlliedSignal.

Based on Carbon nanotubes (bucky tubes).

Sub-microscopic Carbon sheets (formed into tubes) filled with electrolytes.

Nanotube Artificial Muscle (cont’d)

When a voltage is applied the sheets contract to do work.

Possible limitation: electrically actuated.

Being investigated by Defense Advanced Research Projects Agency (DARPA) as “bucky paper”.

Polyacrylonitrile (PAN)

Combination of gel and plastic. Tough.Contracts under pH changes.Contraction occur in 20 ms to a -20% strain.Very similar to human muscle in speed, exceeds human muscle in max force per cm2 (2x).

Polyacrylonitrile (PAN) (cont’)

Must be surrounded by solutions in latex tubes.

Some models have been developed which simulate muscle movement.

University of NM project.

Electro-active Muscle Transducers

Uses compliant electrodes to electrically stimulate electro-active elastomeric materials.

Produce strains in excess of 100%, and pressures greater that 100 psi.

Spherical joints have been developed based on the actuator.

Developed by SRI International, Inc.

AKA Electrostrictive or dielectric elastomer.

Exhibit a mechanical strain when subjected to an electrical field.

Striction capability exceeds piezoelectric ceramics.

Most common are PMMA-based.

Produce a positive force/expansion.

Use: tiny robotic muscles.

Electro-active Muscle Transducers (cont’d)

A Novel Use for AM

Smart implants with tiny perforations that contain a pharmaceutical, plugged by artificial muscles.

The implant has tiny sensors which sense blood concentrations of certain chemicals.

A Novel Use for AM (cont’d)The artificial muscle then will shrink to allow a drug to pass freely.

When concentrations of the sensed chemical rises in the blood, the muscle then relaxes to plug the holes a gain.

Honorable Mention Replacement: Prosthetic

LimbsStarted as passive replacements to fill clothing or act as support. Archeological evidence of prostheses in ancient India and

Egypt--Queen Vishpla, Elis. Infection and blood loss.

1600’s-1800’s Great increase in health technology: styptic antibiotics,

anesthetics, blood clotting chemicals. Prosthetic units were developed with lighter weight and greater

articulation (motion learned and controlled by amputee).

1940’s-1980’s – Emphasis on actuation.1980’s-Present – Emphasis on realism.

Replacement: Prosthetic Limbs (cont’d)

Number of Companies that specialize in prosthesis/orthotics: North Shore Orthotics-Prosthetics, Inc. Ohi, SCOPe, many others.

Limb replacements are actuated: By other existing muscles directly. By EMG generated by nearby existing muscles Balance.

Artificial Muscle

Applications in Robots

Types of Robots

Miniature robots

Wall climbers

Exploring rovers

Miniature Robots

Submersible bots with plastic muscles

Ability to someday pick up single cells

Positive and negative ions shrink and swell the polymer

Wall Climbers

Air Rubbertuator

Capable of difficult inspections

Aircraft

Bridges

Nuclear power plants

Obstacles, inclines, stairs, vertical movement.

Robots in Space

Ability to probe, dig, photograph and analyze

No gears or complex mechanical systems

Lighter and less complex robots

Smaller

Not sensitive to dust

Capabilties

Grasping

Wiping

Muscle groups working together

Grasping

Electric charge applied to plastic ribon

Charged particles pushed to one side lengthens that side

Wipers

Two-way wiping motion produced

Applications onto cameras or sensors

Muscles Working Together

Creates more than one motion

Bionic men and women???

Could replace human muscles

Legs and Wheels

Able to handle most terrain

Durable

Reliable

Not as good as four legs

A Way of the Future

Cheap

Durable

Lightweight

Conserve Power

References

Electroactive Polymer Actuators webpage

Artificial Muscle Research Institute

SRI International, Inc.

Opthalmatronix, Inc.

Ohio State University

www.spacedaily.com

Max Planck Society

University of New Mexico -- cape.uwaterloo.ca

BBC News

Science Daily

Discovery Channel