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SUMMARY:Carbon Nanotube Mechanics: nano and macro\; liquid and solid\; sti
 ff and soft—but always conductive - Prof Pasquali\, Rice University\, Hu
 ston Texas
DTSTART:20190308T140000Z
DTEND:20190308T150000Z
UID:TALK117511@talks.cam.ac.uk
CONTACT:Hilde Hambro
DESCRIPTION:Certain materials properties are viewed as contradictory.  For
  example\, high electrical and thermal conductivity are associated with ha
 rd\, crystalline materials such as metals or graphite.  Conversely\, softn
 ess is associated with biological materials\, polymers\, colloids\, and di
 sordered structures\, which are also thermally and electrically insulating
 .  We have essentially accepted that certain ostensible contradictions can
 not be resolved.  For example\, we have no material that is electrically c
 onductive and can be sutured or sewn\, despite the obvious need in medical
  devices and wearable electronics.  This ostensible contradiction has caus
 ed an interesting split between “soft” and “hard” condensed matter
 . Within soft condensed matter\, we split liquids between colloids and sol
 utions—perhaps artificially so.\n\nThe combination of nanoscale properti
 es of “solid” carbon nanotubes (CNTs)\, and their translation at the m
 acroscopic scale\, and their behavior in liquids\, are making us rethink t
 hese artificial divisions between “soft” and “hard”\, and between 
 colloidal and solution behavior in complex fluids. In this lecture\, I wil
 l discuss how CNT in liquid phases can and should be viewed as hybrids bet
 ween polymer molecules and colloidal particles\, and how this approach can
  be used to design directed assembly routes for soft conductors.\n\nEven a
 t minute concentrations\, CNTs form complex fluid phases with intriguing p
 roperties. In ultra-dilute solutions\, CNT behave as ideal semiflexible Br
 ownian filaments\; surprisingly (or not?)\, their bending stiffness follow
 s continuum scaling laws. In crowded environments (e.g.\, gels)\, CNTs rep
 tate like stiff polymers\; surprisingly\, the small bending flexibility of
  CNTs strongly enhances their motion.  In thermodynamic solvents\, slender
  CNTs form liquid crystalline phases at minuscule concentrations.  CNTs so
 lutions can be used for making transparent\, conducting\, flexible films a
 nd coatings\, as well as highly porous\, soft three-dimensional foams.  At
  high concentration\, CNTs liquid crystals can be spun into well-aligned\,
  packed macroscopic fibers.  Because of their near-perfect microstructure\
 , these fibers are ideal for studying the relationship between “molecula
 r” CNT properties and macroscale CNT material behavior. CNT fibers and f
 oams combine high conductivity\, strength\, and the emergent property of s
 oftness. As soft conductors\, CNT fibers provide a natural interface to th
 e electrical function of the body as restorative sutures for electrically 
 damaged heart tissue as well as electrodes for stimulating and sensing the
  activity of the brain.\n
LOCATION:Oatley Seminar Room\, Department of Engineering
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