1. Engineering Carbon Nanotube Fibers by a Mechanical Twisting Method Graduate Research Mentor, Ji Hao, Northeastern University Gary Hu, YSP Student, North Quincy High School James Zhou, YSP Student, Andover High School Professor Yung Joon Jung, Mechanical and Industrial Engineering, Northeastern University

2. Carbon Nanotubes (CNTs) High tensile strength Stiffest material yet discovered High strength to weight ratio

3. What’s the Problem? Current applications limited Strength does not scale Manufacturing deformities Poor alignment

4. Twisting Fibers Improves alignment Increases uniformity Distributes force Greater strength

5. Purpose To design a fiber twisting apparatus To compare mechanical properties of twisted and untwisted fibers To investigate the morphological effect of twisting fibers

6. Our Fiber Microscopic image of pristine CNT fiber (Diameter: ~800 μ m) (bottom left) SEM image inside small bundles of CNT (Diameter: ~10-100nm) (bottom right) TEM image of individual DWNTs and TWNTs (Diameter: ~5nm) (upper right)

7. STP-PWR-3204 (power source) STP-DRV-405 (micro-stepping drive) 6221 SourceMeter (DC source) DWNT/ TWNT fibers STP-MTR-17040 (micro-stepping motor) AC 110V (outlet) Computer with LabVIEW 2011 SP1 Schematic of the Motor Setup

8. (b) Overhead view of the fiber clamps(a) Entire motor system (c) Fiber cutting procedure

9. Morphological Data Larger twisting angles Smaller diameter Greater fraying

10. (b) The dependence of fiber diameter on the number of cycles (a) The dependence of twisting angle on the number of cycles

11. Mechanical Testing Data More cycles— stronger fiber Occasional failure

12. Conclusion and Future Work Twisted fibers have higher performance Fraying and other defects limit the extent of useful twisting Improve setup Reduce deformities Change motor frequency Control angle and diameter individually

13. Acknowledgements Center for STEM Education Young Scholars Program & Team Claire Duggan – Director Maureen Cabrera, Madeline Leger – YSP Coordinators Yung Joon Jung – Advising professor Ji Hao – Graduate student mentor

14. References Kai Liu et al, Nanotechnology 21, 045708 (2010). Yu MF et al, Science 287, 637–640 (2000). Zhang M, Atkinson KR and Baughman RH, Science 306, 1358-1361 (2004).

15. Any questions?