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Change in Stripes for Cholesteric Shells via Anchoring in Moderation

Phys. Rev. X 7 (2017) 041029, by Lisa Tran, Maxim O. Lavrentovich, Guillaume Durey, Alexandre Darmon, Martin F. Haase, Ningwei Li, Daeyeon Lee, Kathleen J. Stebe, Randall D. Kamien, and Teresa Lopez-Leon

Chirality, ubiquitous in complex biological systems, can be controlled and quantified in synthetic materials such as cholesteric liquid crystal (CLC) systems. In this work, we study spherical shells of CLC under weak anchoring conditions. We induce anchoring transitions at the inner and outer boundaries using two independent methods: by changing the surfactant concentration or by raising the temperature close to the clearing point. The shell confinement leads to new states and associated surface structures: a state where large stripes on the shell can be filled with smaller, perpendicular substripes, and a focal conic domain (FCD) state, where thin stripes wrap into at least two, topologically required, double spirals. Focusing on the latter state, we use a Landau-de Gennes model of the CLC to simulate its detailed configurations as a function of anchoring strength. By abruptly changing the topological constraints on the shell, we are able to study the interconversion between director defects and pitch defects, a phenomenon usually restricted by the complexity of the cholesteric phase. This work extends the knowledge of cholesteric patterns, structures that not only have potential for use as intricate, self-assembly blueprints but are also pervasive in biological systems.

General News

  • Helen Ansell awarded Department of Physics and Astronomy's 2018 Werner B. Teutsch Prize, Awarded annually to the graduate student who, by his or her performance in the first year courses, shows the most promise for outstanding achievement in research. (June 2018)

  • Hillel Aharoni wins 2018 Michi Nakata Prize for Early Career Achievements of the International Liquid Crystal Society For his impressive evolution of research on topological and geometric applications in soft matter physics from the pattern formation in smectic liquid crystals, demonstrating how nature uses simple geometric principles for achieving complex functionality. His unusual broad view on the soft matter physics including liquid crystal physics, based on strong mathematical and geometrical skills, will make him grow as a prominent scientist. (June 2018)

  • Ex-postdoc Tom Machon wins 2018 Glenn Brown Dissertation Prize of the International Liquid Crystal Society For his theoretical work on the topology and field states in soft matters, especially in complex liquid crystalline environments, with the goal to predict and determine topological properties of the objects such as field knots and topological defects. Another aspect of his contribution to soft matters, the stability of minimal surfaces, opens up a fascinating new field at the intersection of physics and mathematics. (June 2018)

  • Ex-student Dan Beller accepts faculty position at UC Merced! (June 2018)

  • Lisa Tran successfully defends thesis! (April 2018)

  • Lisa Tran awarded 2018 Elias Burstein Prize "for the exquisite control and deep understanding of complex liquid crystalline materials." (March 2018)

  • Lisa Tran accepts faculty position at Bryn Mawr! (February 2018)

  • Lisa Tran chosen as a Simons Junior Fellow! (December 2017)

  • Lisa Tran takes fifth place in Nikon Small World in Motion Competition! (September 2017)

  • Tom Machon accepts faculty position at University of Bristol! (July 2017)

  • Lisa Tran awarded American Association of University Women Dissertation Fellowship! (May 2017)

  • Ex-postdoc Mohamed Gharbi accepts faculty position at UMass Boston! (May 2017)

  • Former student Carl Modes accepts Research Group Leader Position at MPI Dresden! (April 2017)

  • Max Lavrentovich accepts faculty position at University of Tennessee Knoxville! (April 2017)

  • Lisa Tran receives Dissertation Completion Award from the School of Arts and Sciences! (March 2017)

  • Graduate Student Lisa Tran chosen as GSNP Student Award Finalist. (December 2016)

  • Ex-postdoc Chris Santangelo wins 2017 GSOFT Early Career Award For seminal theoretical contributions exploiting geometry and topology to understand the elasticity of soft materials. (October 2016)

  • Daniel Beller wins 2016 Glenn Brown Dissertation Prize of the International Liquid Crystal Society For his outstanding theoretical work to identify the rich possibilities and outcomes of controlling defects in nematic and smectic liquid crystals under a variety of boundary conditions. The demonstration of the well controlled disclinations and focal conics is expected to open up a novel route for self-assembly in soft-ordered materials . (June 2016)

  • Tom Machon arrives from England. Welcome! (May 2016)

  • Sabetta Matsumoto accepts faculty position at Georgia Tech! (May 2016)

  • Francesca Serra accepts faculty position at Johns Hopkins University! (March 2016)

  • Randy Kamien awarded G.W. Gray Medal of the British Liquid Crystal Society. (February 2016)

  • Hillel Aharoni arrives from Jerusalem. Welcome! (August 2015)

  • Tingting Gong chosen as Apker Award Finalist! (July 2015)

  • Tingting Gong chosen as 2015 Dean's Scholar! (January 2015)

  • Max Lavrentovich arrives from Cambridge, MA. Welcome! (September 2014)

  • Daniel Sussman receives American Philosophical Society Post-Doctoral Fellowship in Advanced Materials! (June 2014)

  • Tingting Gong chosen as a Vagelos Challenge Awardee! (May 2014)

  • Ex-postdoc Simon Čopar wins 2014 Glenn Brown Dissertation Prize of the International Liquid Crystal Society For his outstanding thesis describing a new theoretical approach, whereby the combination of local defect geometry and topological properties of nematic disclinations networks allows for a complete theoretical description of arbitrary complex nematic braids. (May 2014)

  • Daniel Beller succesfully defends thesis. Hurray! (April 2014)

  • Ex-postdoc Gareth Alexander awarded British Liquid Crystal Society Young Scientist Award. (April 2014)

  • Toen Castle arrives from down under. Welcome! (March 2014)

  • Dan Beller has been awarded the George F. Carrier fellowship in Harvard's School of Engineering and Applied Science, an endowed honorific postdoctoral position in widely applied mathematics. (February 2014)

  • Dan Beller accepts postdoctoral position at Harvard University. (January 2014)

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