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VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
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SEQUENCE:0
UID:UW-Physics-Event-2093
DTSTART:20110218T220000Z
DURATION:PT1H0M0S
DTSTAMP:20260420T134722Z
LAST-MODIFIED:20110124T181736Z
LOCATION:2241 Chamberlin Hall (coffee at 3:30 pm)
SUMMARY:Regular and Irregular Polyhedra in Multi-Component Crystalline
  Shells\, Physics Department Colloquium\, Monica Olvera de la Cruz\, N
 orthwestern University\, Department of Materials Science and Engineeri
 ng
DESCRIPTION:The captivating charm of uniform convex polyhedra such as 
 Platonic and Archimedean solids has beguiled scientist\, philosophers\
 , and artists for millenia. In our modern era\, it is incorporated in 
 the revolutionary Descartes' geometrization of nature\, and still refl
 ects the common practice of introducing esthetic elements in physical 
 sciences. While mathematicians have rigorously captured the "morpholog
 ical essence" of such highly regular polytopes by classifying and form
 alizing their symmetries and isometries\, the search of such structure
 s in the realm of nature has been rather elusive. Icosahedral shapes\,
  among all Platonic polyhedrals\, have been identified in molecular el
 astic shells such as large viral shells or fullerenes. We demonstrate 
 that other geometries\, including some Archimedean polyhedrals\, arise
  spontaneously in shells formed by more than one component. We study t
 he buckling of an elastic shell with two coexisting elastic components
 \, at different relative concentrations. By using theoretical argument
 s and numerical simulations we find various polyhedra and n-gonal hoso
 hedra shapes. Our work explains the principles to design various hallo
 w polyhedra and the existence of the regular and irregular polyhedra s
 hells recently observed in organelles. Our analysis suggests that thes
 e polyhedral shapes are ubiquitous in cellular shells and in closed el
 astic membranes made of various proteins. We provide experimental evid
 ence of the spontaneous buckling phenomena in shells made of mixtures 
 of cationic and anionic amphiphiles\, where electrostatics drives thei
 r co-assembly\, and orders the assembly into faceted ionic structures.
  
URL:https://www.physics.wisc.edu/events/?id=2093
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