University:
Boston University
Course:
CAS PY 105 | Physics 1
Academic year:

2021
Views:

229

Pages:

18
Author:

garrotar4i3

Lesson engagement • How would you choose to test your blood? Nanotubes as Biosensors • Carbon nanotubes can be modified to detect many molecules found in the blood • Small size means that encapsulated nanotubes can be implanted at any site • New glucose detector that takes advantage of CNT fluorescence and small size Example: Glucose Sensor This glass capillary tube, shown here on a fingertip, has been loaded with glucose-sensitive nanotubes. The capillary tube keeps the nanotubes confined, but has porous walls so that glucose molecules can get to them. (Credit: Michael S. Strano) • Carbon nanotube modified with “sensor” molecules • RESULT: More glucose Æ More fluorescence Another Exciting Property of CNTs • Nanotubes make excellent filters Small pore size High Surface Area to Volume Ratio Easy to Modify • Seldon, Technologies (Windsor, VT) has created several nanotube filters • Removes chemicals • Kills and removes bio-contaminants Carbon Nanotube ““Kill-zone” Kill-zone” • Seldon Technologies created a CNT-based filter: Don’t need high pressure “Kill-zone” that is an absolute barrier to biocontaminants • Monolayer nanomesh blocks debris without stopping water flow Making Your Own Monolayer CNT Monolayer Nanotubes Bacteria Ratio 60 nm 2 μm 0.03 Sticks Marbles Ratio 1 mm 1.25 cm 0.08 TUMBLE game ($9.99) Antibacterial Properties Applications for the Military • Prototype built as a “backpack” • United States Air Force currently testing the device • Can filter large volumes of water from dirty sources (EVEN URINE!) Safe Water Available Anywhere Physics of Carbon Nanotubes • Maximum Tensile Strength ~ 30 GPa • Density normalized strength of a carbon nanotube is ~56 times that of steel wire • CNT can carry large currents with little heating What are Composite Materials? • Composite materials are materials made from two or more components • A composite material usually consists of a strong fiber and a matrix (which surrounds the fiber) • The fiber carries the load while the matrix keeps fibers in the correct position and protects the fibers from environmental damage. • Examples of fibers: fiberglass, Kevlar • Examples of a matrix: polyester, epoxy Carbon Nanotubes in Composite Materials • • CNT can act as a strong fiber to improve the strength, elasticity, and conductivity of a material. Challenges Dispersing the nanotubes uniformly throughout the matrix Reducing intratube sliding in MWNT Creating adhesion between the carbon nanotube and the matrix that results in an effective stress transfer Mechanical Properties and applications of Carbon nanotubes ((CNTs) CNTs) • Mechanical properties: (1nm to 100s nm) Light weight, sustains extremely high tension force; 130 GPa compared to steel at <5 GPa Highly flexible, even under low temperature. • Applications: AFM tips, super-strong fabrics, polymer composites and space elevator Nakayama CNT in Action Applications of CNT Composites • Babolat Tennis Rackets • Easton uses CNT in baseball bats • Nissan’s X-Trail SUV has bumpers that are reinforced with CNT • Wings on NASA’s Morphing Glider CRT Televisions In an older TV (CRT) a cathode emits electrons towards an anode and onto a phosphor screen. One electron beam serves the entire screen and the direction of the beam was manipulated by magnetic coils. How does a Field Emission Display differ from a CRT? An FED has electron emitters behind every pixel. Field Emission Displays How is an FED different from an LCD? Lower power consumption, higher brightness, wider viewing angle. Why are carbon nanotubes a good choice in an FED? Nanotubes are able to generate a high electric field due to their small tip They are stable emitters with a long lifetime. Nanoscale electronics • Transport properties: High thermal conductivities w/o electrical conductivity, Semiconducting or metallic tubes, High current density (1000X Cu). • Applications: • field emission devices => field emission flat panel. • single molecular transistors