Magnetic tweezers for captive disclination loops

• Autor(a) principal: Cabeça, Rui Filipe de Jesus
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/24815
• topic: Nematics; Loops; Fibers; Fields; Manipulation; Anchoring; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia dos Materiais

It is known that Liquid crystals (LCs) are very sensitive to external fields, making them very desirable regarding technological applications. The uniaxial nematic phase, with long-range orientational order, is widely studied, presenting molecular alignment singularities known as disinclination lines. The manipulation of these lines opens new perspectives in the LCs field. In fact recent studies showed that what appeared to be a point defect in a nematic liquid crystal, are actually nanometer-sized closed-loops[1], that can selectively trigger self-assemble molecular processes.[2]. The disclination loops appearance as well as position, when threaded on polymeric fibers with axial anchoring, can be precisely controlled. In this work, we present results concerning the generation and precise manipulation these disclination loops, on a micro-scale, threaded on nylon, micro plants cellulose-based filaments and electrospun fibers, immersed in homeotropic nematic cells, with the application of a magnetic field.