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SUMMARY:Living photonic devices from patchy colloids: Inspiration from cep
 halopods - Alison Sweeney\, University of Pennsylvania
DTSTART:20140314T140000Z
DTEND:20140314T150000Z
UID:TALK50340@talks.cam.ac.uk
CONTACT:Alessio Zaccone
DESCRIPTION:"Patchy colloids" are systems in which constituent particles e
 xhibit rich phase and assembly behavior due to the anisotropic distributio
 n of attractive and repulsive "patches" on particle surfaces.  These syste
 ms show great promise for generating sophisticated new\, self-assembled ma
 terial properties\, but the colloidal particles used in current experiment
 al systems are typically micron-scale or larger\, limiting the range of ma
 terial properties that can be explored.  Globular proteins are an intuitiv
 e choice for roughly spherical particles an order of magnitude or more sma
 ller than currently tractable colloidal patchy particle systems\, but natu
 rally evolved proteins are typically strongly selected to avoid disordered
  aggregation to avoid poisoning the cells which must make them.  However\,
  cephalopods have evolved a diverse array of complex optical and photonic 
 structures that appear to self-assemble from globular proteins interacting
  as patchy colloids.  Therefore\, we explore naturally evolved\, self-asse
 mbling photonic systems in cephalopods as inspiration for novel hierarchic
 ally ordered\, self-assembling materials.\n\nOur preliminary evidence sugg
 ests that the self-assembling photonic devices in cephalopods are structur
 ed in a manner consistent with theoretical predictions from the patchy col
 loid framework.  In particular\, the squid lens system appears to have evo
 lved a system of patchy proteins of continuously decreasing average coordi
 nation number with lens radius\, resulting in a graded refractive index le
 ns from a single-index evolutionary precursor.  This talk will explore exp
 erimental and modeling evidence from the diverse\, living optical systems 
 in cephalopods suggesting that the optical properties of both the graded-i
 ndex lenses in the eyes\, and the sophisticated reflectors in the skin evo
 lved for camouflage may arise from proteins following patchy-colloid-like 
 assembly rules.  
LOCATION:Small Lecture Theatre\, Cavendish Laboratory
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