{"id":195,"date":"2017-08-24T09:41:28","date_gmt":"2017-08-24T01:41:28","guid":{"rendered":"http:\/\/sheng.people.ust.hk\/?p=195"},"modified":"2017-09-13T00:31:31","modified_gmt":"2017-09-12T16:31:31","slug":"liquid-crystals","status":"publish","type":"post","link":"http:\/\/sheng.people.ust.hk\/?p=195","title":{"rendered":"Liquid crystals"},"content":{"rendered":"<ul>\n<li>Pioneered in the study of substrate-induced phenomena in nematic liquid crystals,\u00a0with predictions verified by subsequent experiments.<\/li>\n<\/ul>\n<p><span style=\"color: #000000;\">Alignment of liquid crystal&#8217;s orientational order, through its interaction with the substrate, is a critical element in liquid crystal (LC) displays.\u00a0\u00a0As an extension of the pioneering study on such interactions [1,2], the recent research focus on this topic is on the use of micro \/ nanotextured substrates for producing uniform alignment of nematic LC&#8217;s orientational ordering [3,4].\u00a0\u00a0The basic principle underlying this approach is &#8220;frustration,&#8221; i.e., when the elastic energy required for the boundary LC layer to following the micro \/ nanotextured pattern exceeds a certain threshold, it becomes energetically favorable to sacrifice the interfacial interaction energy so as to minimize the elastic energy, by making a transition to a uniform alignment.\u00a0\u00a0What we have found is that by using such micro \/ nanotextured substrates, one can achieve large pretilt angles, e.g., on the order of 40 degrees (between the symmetry axis of the nematic LC and the substrate).\u00a0\u00a0This has been experimentally verified [4].\u00a0\u00a0Large pretilt angles are useful for making bistable LC displays, with the advantage of energy savings.<\/span><\/p>\n<p><!--more--><\/p>\n<figure id=\"attachment_196\" aria-describedby=\"caption-attachment-196\" style=\"width: 960px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" class=\"size-full wp-image-196\" src=\"http:\/\/sheng.people.ust.hk\/wp-content\/uploads\/2017\/08\/Liquid-Crystal.jpg\" alt=\"\" width=\"960\" height=\"628\" srcset=\"http:\/\/sheng.people.ust.hk\/wp-content\/uploads\/2017\/08\/Liquid-Crystal.jpg 960w, http:\/\/sheng.people.ust.hk\/wp-content\/uploads\/2017\/08\/Liquid-Crystal-300x196.jpg 300w, http:\/\/sheng.people.ust.hk\/wp-content\/uploads\/2017\/08\/Liquid-Crystal-768x502.jpg 768w\" sizes=\"(max-width: 960px) 100vw, 960px\" \/><figcaption id=\"caption-attachment-196\" class=\"wp-caption-text\">AFM topographical images of several microtextured substrates we fabricated<\/figcaption><\/figure>\n<p><strong>Key publications:<\/strong><\/p>\n<ol>\n<li>&#8220;<strong><a style=\"color: #1252ba;\" href=\"http:\/\/sheng.people.ust.hk\/wp-content\/uploads\/2017\/08\/Phase-Transition-in-Surface-Aligned-Nematic-Films.pdf\">Phase Transition in Surface-Aligned Nematic Films<\/a><\/strong>&#8220;, Ping Sheng, <em>Phys. Rev. Lett.<\/em> 37, 1059 (1976).<\/li>\n<li>&#8220;<strong><a style=\"color: #1252ba;\" href=\"http:\/\/sheng.people.ust.hk\/wp-content\/uploads\/2017\/08\/Boundary-Layer-Phase-Transition-in-Nematic-Liquid-Crystals.pdf\">Boundary-Layer Phase Transition in Nematic Liquid Crystals<\/a><\/strong>&#8220;, Ping Sheng, <em>Phys. Rev. A<\/em> 26, 1610 (1982).<\/li>\n<li>&#8220;<strong><a style=\"color: #1252ba;\" href=\"http:\/\/sheng.people.ust.hk\/wp-content\/uploads\/2017\/08\/Liquid-Crystal-Phase-Transitions-Induced-by-Microtextured-Substrates.pdf\">Liquid-Crystal Phase Transitions Induced by Microtextured Substrates<\/a><\/strong>&#8220;, T. Z. Qian and Ping Sheng, <em>Phys. Rev. Lett.<\/em> 77, 4564 (1996).<\/li>\n<li>&#8220;<strong><a style=\"color: #1252ba;\" href=\"http:\/\/sheng.people.ust.hk\/wp-content\/uploads\/2017\/08\/Liquid-Crystal-Orientation-Transition-on-Microtextured-Substrates.pdf\">Liquid Crystal Orientation Transition on Microtextured Substrates<\/a><\/strong>&#8220;, Baoshe Zhang, Fuk Kay Lee, Ophelia K. C. Tsui and\u00a0Ping Sheng, <em>Phys. Rev.\u00a0Lett.<\/em> 91(21),\u00a0215501-4 (2003).<\/li>\n<\/ol>\n<p>&nbsp;<\/p>\n<ul>\n<li>Resolved the classical puzzle in the theory of nematic liquid crystals, with the formulation of an extended mean field theory.<\/li>\n<\/ul>\n<p><strong>Key publication:<\/strong><\/p>\n<ol>\n<li>&#8220;<strong><a style=\"color: #1252ba;\" href=\"http:\/\/sheng.people.ust.hk\/wp-content\/uploads\/2017\/08\/Nematic-Isotropic-Phase-Transition-An-Extended-Mean-Field-Theory.pdf\">Nematic-Isotropic Phase Transition: An Extended Mean Field Theory<\/a><\/strong>&#8220;, R. Tao, Ping Sheng and Z. F. Lin, <em>Phys. Rev. Lett.<\/em> 70, 1271 (1993).<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"<p>Pioneered in the study of substrate-induced phenomena in nematic liquid crystals,\u00a0with predictions verified by subsequent experiments. Alignment of liquid crystal&#8217;s orientational order, through its interaction with the substrate, is a critical element in liquid crystal (LC) displays.\u00a0\u00a0As an extension of the pioneering study on such interactions [1,2], the recent research focus on this topic is &hellip; <a href=\"http:\/\/sheng.people.ust.hk\/?p=195\" class=\"more-link\">Continue reading <span class=\"screen-reader-text\">Liquid crystals<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[2],"tags":[],"_links":{"self":[{"href":"http:\/\/sheng.people.ust.hk\/index.php?rest_route=\/wp\/v2\/posts\/195"}],"collection":[{"href":"http:\/\/sheng.people.ust.hk\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/sheng.people.ust.hk\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/sheng.people.ust.hk\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/sheng.people.ust.hk\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=195"}],"version-history":[{"count":10,"href":"http:\/\/sheng.people.ust.hk\/index.php?rest_route=\/wp\/v2\/posts\/195\/revisions"}],"predecessor-version":[{"id":996,"href":"http:\/\/sheng.people.ust.hk\/index.php?rest_route=\/wp\/v2\/posts\/195\/revisions\/996"}],"wp:attachment":[{"href":"http:\/\/sheng.people.ust.hk\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=195"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/sheng.people.ust.hk\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=195"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/sheng.people.ust.hk\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=195"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}