Multifunctional Carbon Nanotube Fibers R.H. Baughman1, A.A. Zakhidov1, J. Ferraris1, A.B. Dalton1, M. Zang1 E. Muñoz1, S. Collins1, M. Kozlov1, J. M. Razal1, Von H. Ebron1, D.-S. Suh1, Yu.N. Gartstein1, G.M. Spinks2, N. Barisci2, G.G. Wallace2, M. Kertesz3, L.S. Fifield4, L.R. Dalton4, W. J. Kennedy5, Z. V. Vardeny5 1NanoTech
Institute, Univ. of Texas at Dallas 2Univ. of Wollongong, Wollongong, AU; 3Georgetown Univ., Washington, DC, USA; 4Univ. of Washington 5 Univ. of Utah
Mutifunctional Carbon Nanotube Fiber Composites (DARPA) Outstanding Mechanical Functionality Multifunctiona l Vest
Energy Storage
Adaptive System
Mechanical Actuation and Damping
Micro Air Vehicle
Energy Harvesting
Multifunctional Helmet
GOAL: Demonstrate of carbon nanotube composites combining mechanical functionality with (a) mechanical actuation, (b) energy storage, (c) mechanical dampening, (d) energy harvesting, (e) sensing, and/or (f) camouflage functionalities.
New Multifunctional Material: Single-Wall Carbon Nanotubes Modulus: 6 million kg/cm
(12, 0) Zigzag (10, 10) Armchair (10, 5) Chiral
SPINNING CARBON NANOTUBE FIBERS MUCH STIFFER, STRONGER, AND TOUGHER THAN SPIDER SILK Spider silk properties evolved over 400 Million years to catch missiles (flying insects). The energy absorption capability (energy-to-break) is called toughness. By weight, spider silk is five times tougher that steel wire, leading to century-old commercialization attempts. We can spin continuous nanotube composite fibers that are tougher than any known material – five times that of spider silk.
CARBON NANOTUBE SPINNING Fibers form in coaxial flow field.
French Rotary Bath Process Final fiber winding
Motors Gel Fiber Acetone Wash
First Step of UTD Process: Gel fibers spun continuously and wound on mandrel
Process changes provide: 100X higher rate, 1000X longer length, 16X higher strength, 2X higher modulus, and 500X higher toughness than previously reported.
Second Step of UTD Process: Gel fibers converted to continuous nanotube fiber by reel-to-reel processes (unwinding,acetone wash, drying, winding)
UTD Continuous Flow Spinning Process
NT Spinning Solution
NT Gel Fiber
Gel fiber to solid fiber
NT fiber
TOUGH FIBERS COMPRISE ~60% BY WEIGHT HiPco NANOTUBES AND ~40% POLYVINYL ALCOHOL 1 µm
SEM micrograph showing end of undrawn carbon nanotube fiber (broken in liquid N2). Nanotube fibers are coated with the polyvinyl alcohol matrix polymer.
Mechanical Properties for Our Spun Carbon Nanotube Composite Fibers 1000
3.5 3.0
Nan n Spu
iber F be otu
800
Stress (GPa)
2.5 2.0
ilk S r ide p S
1.5
be u t ano N un p S
er b i F
600
400
1.0 0.5
S
0
10
200
Silk r e pid
20
30
Strain (%)
40
50
60
0
Energy Absorption (J/g)
Strength Toughness NT Fiber 3.2 GPa 600 J/g Kevlar 3.6 GPa 33 J/g Spider silk 1.8 GPa 165 J/g
COMPARISON OF RECENT PERFORMANCE WITH THAT FOR COMPETING FIBERS Fiber Type Carbon Fiber E Glass S Glass Kevlar 29 Kevlar 49 UTD NT FIBER
Density (g/cm3)
Strength (GPa)
Modulus (GPa)
Toughness (J/g)
2.0
2.27
483
12
2.59 2.49 1.44 1.45
3.44 2.60 2.92 3.0
72 80 70.3 112
1.5
3.2
85
15-30 15-30 37 25 600 (56% strain)
Total Fiber Toughness > 1000 J/g !
Tougher Than Any Other Material
WHY IS FAILURE STRAIN SO HIGH? Fiber Necking Does Not Occur ⇒ Strain Rate Directly Proportional to Applied Stress. 130
Newtonian flow!
Stress (MPa)
120 110 100 90 80 0
2
4
6
8
Strain Rate (%/min) at 40% Strain
10
TOUGHNESS MECHANISM Toughness might be due to unraveling of polymer wrapped on nanotubes and nanotube bundle thinning.
TGA derivative curve and microscopy shows two different types of PVA (likely wrapped on nanotubes and between nanotubes)
SWNTs Strain
Disordered Polymer Chain
Temperature (°C)
We can now spin fibers comprising MWNTs or DWNTs Strength (unoptimized) is 600 MPa. BROKEN ENDS OF THE MWNT HYBRID FIBER
ELECTRONIC TEXTILES: SUPERCAPACITORS IN FABRICS Supercapacitor of electrolyteseparated helically-wound CNT fibers
CNT fiber woven into fabric
CNT fiber supercapacitor woven into fabric
0.6 Wh/kg (1 V charge) and 1200 cycles demonstrated for supercapacitor.
Some possible additional functionalities for fabrics • Sensing (chemical and mechanical stress) • Woven electronic interconnects • Textile actuation (including porosity control) • Thermal conductivity • Camouflage and electromagnetic shielding
Dry Spinning
Dry Spinning MWNT fibers
Nanotube Fibers With a Twist
Patterned MWNTs Line width 8 µm 5 µm 2 µm
Line width 5 µm
90 µm 90 µm
2 µm
Pattern for FE
100 µm
C2H2 is the carbon source, Fe is the catalyst, and a Si wafer is the substrate. The reaction temperature is around 680° C for 10 minute deposition.
The Actuator, Energy Storage, and Energy Harvesting Functions Use Electrochemical Charge Injection ENERGY STORAGE C= charge/voltage C= Area × dielectric constant /d Area/weight is above 300 m2/gm; d is in nanometers ACTUATION Charge injection causes change in fiber length, which does work. Work/cycle ∝ (strain)2 × Y or Work/cycle ∝ strain × σfailure Y, σfailure , and strain are all large.
Charge Injection Changes Properties
Charging Process Can Be Very Fast 800
Current as measured during five-second pulse 0 to 0.4 V, followed by five-second pulse 0.4 to 0 V. Current direction is inverted for the second five-second pulse.
600
Ig
400
i = (E/Rs) e-t/RC
0.0 to 0.4 V
A/g 200 0.4 to 0.0 V 0 0
20
40
60
80
100
t ms
• Above data provides RC of ~15 ms • Rate (linear with sheet thickness) can be dramatically increased by decreasing sheet thickness.
Actuation of HiPco Fiber (45mm diameter) in Organic Electrolyte: Force vs. Potential (Ag/Ag+)
Stress vs. Potential Change 15
Stress (MPa)
Load 21.3 MPa -1.5V
-1.0V -0.5V -0.25V
Load: 21.3 MPa
-2.0V 10
5
-3.0V -2.5V 0 0
1
2
3
Potential Increase (to +0.5V)
Maximum Stress Generated is 26 MPa, about 100 times that of natural muscle.
OUR NANOTUBE ACTUATORS ALREADY GENERATE 100 TIMES THE FORCE OF NATURAL MUSCLE. (3 times the max. stress of natural muscle in 6 msec) STRAIN RATE (20%/s) IS TWICE NATURAL MUSCLE.
Isometric Tests With Resistance Compensation Give Extremely High Effective Strain Rate Load Cell
Fixed Sample Length
Madden and Barisci Data
1 MPa stress generated in 6 msec Stress rate is 160 MPa sec-1. Strain rate is (dσ/dt)/Y=19% sec-1. Our best pre-program results were 23 MPa sec-1 and 0.3% sec-1. Now: 3 times the max. stress of natural muscle in 6 msec.
LARGE ACTUATORS POTENTIAL • Gravimetric work capabilities ten times ferroelectrics. • Stress generation capabilities ten times ferroelectrics. • Cycle life should be large. • Large stroke (above 1%). • Ten times lower needed voltage than ferroelectrics. • Operation to above 1000º C. SOME POSSIBILITIES •Actuation for hostile environments (temperature or radiation): aircraft engines, down hole, planetary exploration •Man-like robotics (prosthetics, body assists, artificial heart)
Today’s Tools for Minimally Invasive Surgery:
Picture from Intuitive Surgical
SOME ACTUATOR APPLICATIONS MECHANICAL ASSISTS (Soldier and handicapped) Sensor Patches Actuating Fibres
ADAPTABLE SURFACE 1) BRAILLE DISPLAY 2) CONTROL OF HYDRODYAMICS FOR MICRO AIR AND MICRO MARINE VEHICLES
Honeywell electromechanical switch Cantilever fiber
Fiber harness Passive alignment features
DEMONSTRATED NANOTUBE OPTICAL FIBER SWITCH Nanotubes glued to optical fiber
Posts
Plunger/spring Coil
+ Counter-electrode is in electrolyte, which matches fiber n.
Materials • Multi-mode optical fiber: 62.5 µm core, 125 µm outer diameter • Actuator: 25 µm thick, 1 mm wide, 3 cm long SWNT strip • Adhesive layer: Five minute epoxy
Fifield/Zipperer/Baughman/L. Dalton
Optical Fiber Switching Using Carbon Nanotubes Optical fiber switching occurs in a two-fiber wide channel in polydimethylsiloxane on a glass substrate. The electrolyte is 4M NaCl. An 58.9 wt % LiBr solution in water closely matches The refractive index of the optical fiber. The counter-electrode (not visible) is a strip of SWNT paper.
Fiber 1 Intensity (AU) Fiber 2 Intensity (AU) Potential (Vvs Ag/AgCl)
NT-Actuator-Based Optical Fiber Switch
200 150 100 50
Low operation voltage (~1 V).
0 -50 250
Low operation power (~50 mW).
200 150 100
LU and YA