Presentation on theme: "Competing With Nature: Smart Muscles Group 8: Alejandra Europa, Leigh Martin, Nidia Selwyn, Jack Bobzien Texas A&M University Chen 313 – Special Project."— Presentation transcript:
Competing With Nature: Smart Muscles Group 8: Alejandra Europa, Leigh Martin, Nidia Selwyn, Jack Bobzien Texas A&M University Chen 313 – Special Project Spring innovations.blogspot.c om/2009/11/carbon- nanotube-artificial- muscles-for.html Mr. Alvin Quiambao, Air Force Office of Scientific Research
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o A muscle is a bundle of many cells called fibers whose function is to produce force and cause motion. o Efficient at turning fuel into motion o Long-lasting o Self-healing o Able to grow stronger with practice o Basic action is contraction / Muscle Power
Artificial muscles are man’s attempt to duplicate, improve or simply replace the role of natural muscles A “muscle” is anything which accomplishes actuation/contraction under the command of a stimulus. First artificial muscle developed in the 1950's by American physician Joseph L. McKibben originally intended to actuate artificial limbs for amputees Artificial Muscles Rehabilitation glove with artificial muscles. art.com/archives/2004/11/the -bionic-glov.php
Currently Implemented o o Mechanical artificial muscles are contractile or extensional devices operated by pressurized air filling a pneumatic bladder, using motors or hydraulics
Alternatives A shape-memory alloy is an alloy that "remembers" its original, cold-forged shape: returning to it when heated. Electroactive Polymers, or EAPs, are polymers that exhibit a change in size or shape when stimulated by an electric field. Dialectric Elastomer IMPC’s Carbon Nanotubes create-artificial-muscles/
BASIC PRINCIPLES Contraction & Expansion of the Natural Muscle K
Muscles are the "engine" that your body uses to propel itself. Turn energy into motion. Contractions of muscles are triggered by electrical impulses or a stimulus Nerve cells Internal or external stimuli com/tags/neuroscience/ MUSCLES Triggered nerve cells.
NATURAL MUSCLES Long-lasting and Self-healing Grow stronger with repetitive use Allows for work cycles of more than 20% Alter strength and stiffness when needed Generate stresses up to about.35 MPa Contract at 50% per second Can transform ATP into fuel, if needed content/uploads/2012/03/contracting- muscles.jpg
Artificial Muscles Materials that change size and shape when activated by a stimulus Mimic natural body functions Provide large force and motion while being lightweight and not very dense Allow for more delicate movements than machines can achieve Early McKibben Arm Muscle of a Rubber Tube
CURRENT TECHNOLOGY com/media/280066/view
History External, lower-extremity orthotic and prosthetic (O&P) devices have been around for centuries Made from crude materials Wood and leather Heavy, non-adaptive, and difficult to use 1970s: Actively controlled knee dampers Advantage over mechanically passive knee systems More control & stability Recently: Computer-controlled adaptive knee orthotic Offers only locking and unlocking controllability This prosthetic toe dates back to between 950 and 710 B.C. Prosthetic toe: 950 and 710 B.C.
History 1988: Popovic and Schwirtlich Amputees using a powered knee prosthesis could walk at faster speeds Improved metabolic economy compared to conventional knees Knee design was never commercialized Problems occurred with the mechanical system Inadequate cycle life Excessive mechanism noise Limited battery life knees/power-knee/
Current Devices Contemporary O&P limbs cannot yet perform as well as their biological counterparts, Stability Power generation Efficiency Cycle life Current prosthetic and orthotic devices are separate, lifeless mechanisms Robotic limbs are bulky and do not yet mimic the natural movement of the body Devices today have no real neurological or intimate connection with the human body 076_A_Navy_Hospital_Corpsman_from_Wounded_Warriors_Battalion_West_s hows_his_prosthetic_leg_during_a_halftime_presentation_at.jpg
Issues Most devices in use today employ a force- controllable actuator Comprised of an electric motor and a mechanical transmission Heavy, bulky, and noisy mechanism Lower-extremity O&P devices cannot modulate spring stiffness and motive force needed for normal leg movement Fit/Sizing Balance Easily fatigued
Solution The actuator and transmission play a dominant role in determining the dynamic performance of O&P devices In trying to duplicate the form and function of a limb, actuators that are similar to natural muscle are needed Desired changes: Lighter Simpler More natural looking Quiet operation Comfortable attachment Lower cost help-improve-control-of-prostheses-video.html
Solution For artificial appendages to truly mimic biological function, even during level ground ambulation, O&P actuators must control both joint impedance and motive force Artificial muscles offer considerable advantages to the physically challenged, allowing for joint impedance Motive force controllability Noise-free operation l/clipping/Scientific-Ameican-article-Oct-03.pdf
CURRENT RESEARCH Picture taken from Clip Art
Properties Needed Generate large strains rather than high force Fractional changes of muscle length ~ 20 % High response rate High output power at low strain
How can this be accomplished? Do not want to mimic nature Large macroscopic strains Combining effects of trillions of molecular actuators Take advantage of material deformations Different types exist Use distinct actuators / driving factors Different contractions levels of an air muscle designed by the Schadow Robot Company.
Types of Actuators Shape Memory Alloys Electroactive Polymers Dielectric Elastomers IPMCs Carbon Nanotubes Taken from Clip Art
Shape-Memory Alloys Commercially important Generate strains of up to 8% Require energy conversion Electrical thermal mechanical Inefficient Shape-Memory Alloy
Problems All previously mentioned artificial muscles provide high-strain But all have a disadvantage Inefficient energy conversion Low response rate High voltages Etc. Need for a new design
Electroactive Polymers EAPs Exhibit change in size or shape when exposed to an electric field Use electronically conducting polymers Polyaniline and polypyrrole High-strain actuators polymers-eap-artificial-muscles-epam-robot-applications
EAPs Solvated dopant ions inserted into a conducting-polymer electrode Similar to a battery Operate at a few volts Generates high strains: 26% High strain rates: 11%/sec Large stresses: 7 to 34 MPa (a) EAP gripping device. (b) A voltage is applied and the EAP fingers deform in order to surround the ball. (c) When the voltage is removed the EAP fingers return to their original shape and grip the ball.
Videos Electroactive Polymer for a Robot Head eap-artificial-muscles-epam-robot-applications
Dielectric Elastomers One type of EAP Resemblance to silicone rubbers in sealants Considered a capacitor Better than a battery Used by Artificial Muscle Inc. Dielectric Elastomer Compresses with applied voltage
Dielectric Elastomers Driven by Maxwell Stress Attraction between charges of opposite capacitor electrodes Repulsion between like charges High strains: 120% Large stresses: 3.2 MPa Peak strain rate: 34,00% / sec for 12% strain mical-e.html
Problems & Limitations As elastomer stiffness decreases, maximum stress generation decreases Maximum actuator stroke and work-per-cycle increases Main limitation High operating voltage needed
IPMC’s Ionic polymer/metal composite actuator Amplifies low strains using the cantilever effect Environmental Robots Inc. Two metal-nanoparticle electrodes Filled & separated with a solid electrolyte EAP Bending
IPMC’s Actuators act as super capacitors Applied electrode potential injects electronic charges into the high surface area electrodes Solvated ions migrate between the electrodes One electrode expands IPMC for sting ray robot - Motion under water
Performance Tensile strength of 40% Actuation results from a local pH change cause by electrolysis of the electrolyte and transport of ions Limitations Low actuation rate Low energy conversion efficiency
Carbon Nanotubes Artificial Muscles Low voltage Low-strain actuators Use electrochemical charge injection into nanostructured electrode Electrostatically driven electrode expansion
How it works Yarns made from sheets of carbon nanotubes Solid guest or filler material in between Replacing liquid electrolytes Melting and solidifying the wax twists or untwist the yarn Generation of motion Actuated by heating
Heat causes a phase transition and volume expansion of wax Yarn provides good electrical conductivity Control of heating and actuation How it works
Performance 100 times the stress of natural muscles Comparable actuation rates Actuator strain is at best 2% Outperforms existing muscles Allows for linear and rotary motions Bundle of Carbon Nanotubes
Limitations Lacks biocompability To replace biological muscle Forces generated are limited Need to keep the wax within the yarn Tensile strength of the yarn material Needs better constrain of volume expansion Few defects can reduce strength Can be fixed with thermal annealing Performance of carbon nanotubes
CONCLUSIONS Carbon nanotubes have the brightest future in the artificial muscle world. It allows for the largest variety of movement while maintaining a high durability.
Future Very advanced technology but still behind Nature provides high-strain muscles Things to remember: Fuel cells provide more power than batteries Need to optimize synthesis conditions of carbon nanotubes: longer Compatibility Use same fuel and fuel delivery system as natural muscles
SOURCES Electrically, Chemically, and Photonically Powered Torsional and Tensile Actuation of Hybrid Carbon Nanotube Yarn Muscles. Márcio D. Lima et al. Science 338, 928 (2012); Speeding Up Artificial Muscles. Mark Schulz. Science 16 November 2012: 338 (6109), Playing Nature's Game with Artificial Muscles. Ray H. Baughman. Science 1 April 2005: 308 (5718), Torsional Carbon Nanotube Artificial Muscles. Javad Foroughi. et al. Science 28 October 2011: 334 (6055),