Pub Date : 2021-12-20DOI: 10.1080/21680396.2021.2020181
P. Pieranski
A large part of the scientific legacy of Maurice Kleman concerns topological defects in liquid crystals. Here, we focus on the very first article of Kleman on liquid crystals coauthored with Jacques Friedel and devoted to linear defects in cholesterics discovered in 1921 by François Grandjean who observed them in wedges made from partially cleaved mica sheets. Kleman and Friedel interpreted the thin (single) and thick (double) Grandjean lines as dislocations with Burgers vectors equal respectively to p/2 (half pitch) or p (whole pitch) and have shown that they are composed of pairs of disclinations that they called τ and λ. We report on a recent work accomplished specifically in memoriam of Maurice Kleman, with the aim to show the beauty of nets of Grandjean lines in wedges made of mica sheets. Using crossed cylindrical sheets, we nucleated in a controlled manner dislocation loops of the two kinds persisting indefinitely independently of the local thickness and of the angle of the wedge. In thin wedges, surprisingly, the double dislocation loops are not smooth but contain one or two cusps corresponding to kinks predicted by Kleman and Friedel. Their presence is a fingerprint of the helicoidal symmetry of cholesterics.
{"title":"Cholesteric dislocations in mica wedges","authors":"P. Pieranski","doi":"10.1080/21680396.2021.2020181","DOIUrl":"https://doi.org/10.1080/21680396.2021.2020181","url":null,"abstract":"A large part of the scientific legacy of Maurice Kleman concerns topological defects in liquid crystals. Here, we focus on the very first article of Kleman on liquid crystals coauthored with Jacques Friedel and devoted to linear defects in cholesterics discovered in 1921 by François Grandjean who observed them in wedges made from partially cleaved mica sheets. Kleman and Friedel interpreted the thin (single) and thick (double) Grandjean lines as dislocations with Burgers vectors equal respectively to p/2 (half pitch) or p (whole pitch) and have shown that they are composed of pairs of disclinations that they called τ and λ. We report on a recent work accomplished specifically in memoriam of Maurice Kleman, with the aim to show the beauty of nets of Grandjean lines in wedges made of mica sheets. Using crossed cylindrical sheets, we nucleated in a controlled manner dislocation loops of the two kinds persisting indefinitely independently of the local thickness and of the angle of the wedge. In thin wedges, surprisingly, the double dislocation loops are not smooth but contain one or two cusps corresponding to kinks predicted by Kleman and Friedel. Their presence is a fingerprint of the helicoidal symmetry of cholesterics.","PeriodicalId":18087,"journal":{"name":"Liquid Crystals Reviews","volume":"1 1","pages":""},"PeriodicalIF":5.1,"publicationDate":"2021-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43261584","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-03DOI: 10.1080/21680396.2022.2163515
S. Fumeron, B. Berche, F. Moraes
ABSTRACT Liquid crystals generally support orientational singularities of the director field known as topological defects. These latter modify transport properties in their vicinity as if the geometry was non-Euclidean. We present a state-of-the-art of differential geometry of nematic liquid crystals, with a special emphasis on linear defects. We then discuss unexpected but deep connections with cosmology and high-energy-physics and conclude with a review on defect engineering for transport phenomena.
{"title":"Geometric theory of topological defects: methodological developments and new trends","authors":"S. Fumeron, B. Berche, F. Moraes","doi":"10.1080/21680396.2022.2163515","DOIUrl":"https://doi.org/10.1080/21680396.2022.2163515","url":null,"abstract":"ABSTRACT Liquid crystals generally support orientational singularities of the director field known as topological defects. These latter modify transport properties in their vicinity as if the geometry was non-Euclidean. We present a state-of-the-art of differential geometry of nematic liquid crystals, with a special emphasis on linear defects. We then discuss unexpected but deep connections with cosmology and high-energy-physics and conclude with a review on defect engineering for transport phenomena.","PeriodicalId":18087,"journal":{"name":"Liquid Crystals Reviews","volume":"9 1","pages":"85 - 110"},"PeriodicalIF":5.1,"publicationDate":"2021-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45458574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-03DOI: 10.1080/21680396.2022.2053597
M. Devi, I. Pani, S. Pal
ABSTRACT The long-range orientational order of liquid crystals (LCs) makes them excellent responsive materials for amplification and transduction of various biochemical events occurring at their interfaces. LC interfaces have been vastly explored for sensing of various macromolecules such as endotoxin, proteins, and disease markers. LC-based sensors possess several advantages over conventional methods in terms of not requiring intensive labour, label-free detection, and low-cost fabrication. However, the first challenge is to ensure the specificity of LC response towards a particular analyte. The second challenge is to design sensing platforms for the detection of small molecule analytes with equal selectivity and sensitivity. In this regard, aptamers have emerged as promising recognition probes due to their high binding affinity towards small molecules, high stability over antibodies, and fast response. The integration of aptamer-based sensing with LC interfaces has enabled the detection of deoxyribonucleic acid (DNA) targets, biologically important toxins, environmental pollutants, heavy metal ions, etc., with applicability in clinical samples. In this review, we recapitulate the recent advancements in the design of aptamer-based LC biosensors for the detection of DNA targets (by DNA hybridization), various biomolecules, and metal ions. GRAPHICAL ABSTRACT
{"title":"Liquid crystals as signal transducers for sensing of analytes using aptamer as a recognition probe","authors":"M. Devi, I. Pani, S. Pal","doi":"10.1080/21680396.2022.2053597","DOIUrl":"https://doi.org/10.1080/21680396.2022.2053597","url":null,"abstract":"ABSTRACT The long-range orientational order of liquid crystals (LCs) makes them excellent responsive materials for amplification and transduction of various biochemical events occurring at their interfaces. LC interfaces have been vastly explored for sensing of various macromolecules such as endotoxin, proteins, and disease markers. LC-based sensors possess several advantages over conventional methods in terms of not requiring intensive labour, label-free detection, and low-cost fabrication. However, the first challenge is to ensure the specificity of LC response towards a particular analyte. The second challenge is to design sensing platforms for the detection of small molecule analytes with equal selectivity and sensitivity. In this regard, aptamers have emerged as promising recognition probes due to their high binding affinity towards small molecules, high stability over antibodies, and fast response. The integration of aptamer-based sensing with LC interfaces has enabled the detection of deoxyribonucleic acid (DNA) targets, biologically important toxins, environmental pollutants, heavy metal ions, etc., with applicability in clinical samples. In this review, we recapitulate the recent advancements in the design of aptamer-based LC biosensors for the detection of DNA targets (by DNA hybridization), various biomolecules, and metal ions. GRAPHICAL ABSTRACT","PeriodicalId":18087,"journal":{"name":"Liquid Crystals Reviews","volume":"9 1","pages":"65 - 84"},"PeriodicalIF":5.1,"publicationDate":"2021-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46749389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-02DOI: 10.1080/21680396.2021.1930596
Diana P. N. Gonçalves, M. Prévôt, Şenay Üstünel, Timothy Ogolla, Ahlam Nemati, Sasan Shadpour, T. Hegmann
Chirality of nanomaterials is a rapidly evolving field, largely driven by the unique optical, electronic, magnetic or catalytic properties of plasmonic, magnetic and semiconductor nanomaterials among others. Liquid crystals continue to play a major role in developing a better understanding of their inherent chiroptical properties as well as serving as reporters to quantify and visualize nanomaterial chirality. Furthermore, liquid crystal phases are increasingly explored as potentially tuneable templates for the helical assembly of various types of nanomaterials. This review summarizes recent progress in this area by describing representative examples and key strategies pursued to interface nanomaterial and liquid crystal chirality. These studies focus on a range of organic and inorganic nanomaterials varying in size, shape and composition as well as on both thermotropic and lyotropic liquid crystal phases. Finally, the two materials concepts merge when liquid crystal molecules self-assemble into distinct filamentous chiral nanoshapes capable of templating other nanomaterials. GRAPHICAL ABSTRACT
{"title":"Recent progress at the interface between nanomaterial chirality and liquid crystals","authors":"Diana P. N. Gonçalves, M. Prévôt, Şenay Üstünel, Timothy Ogolla, Ahlam Nemati, Sasan Shadpour, T. Hegmann","doi":"10.1080/21680396.2021.1930596","DOIUrl":"https://doi.org/10.1080/21680396.2021.1930596","url":null,"abstract":"Chirality of nanomaterials is a rapidly evolving field, largely driven by the unique optical, electronic, magnetic or catalytic properties of plasmonic, magnetic and semiconductor nanomaterials among others. Liquid crystals continue to play a major role in developing a better understanding of their inherent chiroptical properties as well as serving as reporters to quantify and visualize nanomaterial chirality. Furthermore, liquid crystal phases are increasingly explored as potentially tuneable templates for the helical assembly of various types of nanomaterials. This review summarizes recent progress in this area by describing representative examples and key strategies pursued to interface nanomaterial and liquid crystal chirality. These studies focus on a range of organic and inorganic nanomaterials varying in size, shape and composition as well as on both thermotropic and lyotropic liquid crystal phases. Finally, the two materials concepts merge when liquid crystal molecules self-assemble into distinct filamentous chiral nanoshapes capable of templating other nanomaterials. GRAPHICAL ABSTRACT","PeriodicalId":18087,"journal":{"name":"Liquid Crystals Reviews","volume":"9 1","pages":"1 - 34"},"PeriodicalIF":5.1,"publicationDate":"2021-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/21680396.2021.1930596","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48926735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-02DOI: 10.1080/21680396.2021.1948927
Yu-Jen Wang, Yi-Hsin Lin
With the help of augmented reality (AR) and virtual reality (VR) systems, users can receive information and connect with each other via near-eye displays (NEDs). However, several challenges need to be addressed, and the optics are the major bottlenecks. Users wearing current NEDs typically suffer from vergence-accommodation conflict (VAC). Furthermore, people with refractive errors need a pair of prescription lenses to clearly see the virtual image and/or environment. Hence, VAC-free AR/VR systems with vision correction functions should be developed. Furthermore, the AR/VR systems must be designed with slim form factors. Liquid crystal (LC) optical elements with a thin form factor have been demonstrated for light modulation in versatile optical systems; thus, LC-based solutions have been proposed for AR/VR systems in the past decade. Herein, we provide a comprehensive review on the existing literature on LC-based optical systems and suggest possible solutions to realize a better NED system. This review provides an overview of the state-of-the-art progress of LC optics in AR and VR systems. It focuses on the fundamental optics of NEDs, origins of VAC and current LC-based solutions, LC lenses for vision correction function, and the guidelines for solving the two aforementioned challenges using LC lenses.
{"title":"Liquid crystal technology for vergence-accommodation conflicts in augmented reality and virtual reality systems: a review","authors":"Yu-Jen Wang, Yi-Hsin Lin","doi":"10.1080/21680396.2021.1948927","DOIUrl":"https://doi.org/10.1080/21680396.2021.1948927","url":null,"abstract":"With the help of augmented reality (AR) and virtual reality (VR) systems, users can receive information and connect with each other via near-eye displays (NEDs). However, several challenges need to be addressed, and the optics are the major bottlenecks. Users wearing current NEDs typically suffer from vergence-accommodation conflict (VAC). Furthermore, people with refractive errors need a pair of prescription lenses to clearly see the virtual image and/or environment. Hence, VAC-free AR/VR systems with vision correction functions should be developed. Furthermore, the AR/VR systems must be designed with slim form factors. Liquid crystal (LC) optical elements with a thin form factor have been demonstrated for light modulation in versatile optical systems; thus, LC-based solutions have been proposed for AR/VR systems in the past decade. Herein, we provide a comprehensive review on the existing literature on LC-based optical systems and suggest possible solutions to realize a better NED system. This review provides an overview of the state-of-the-art progress of LC optics in AR and VR systems. It focuses on the fundamental optics of NEDs, origins of VAC and current LC-based solutions, LC lenses for vision correction function, and the guidelines for solving the two aforementioned challenges using LC lenses.","PeriodicalId":18087,"journal":{"name":"Liquid Crystals Reviews","volume":"9 1","pages":"35 - 64"},"PeriodicalIF":5.1,"publicationDate":"2021-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/21680396.2021.1948927","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46605745","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-02DOI: 10.1080/21680396.2020.1867662
A. Eremin
In recent years, progress in optics and photonics stimulated the rapid development of multifunctional photoswitchable materials. The ability to manipulate the mechanical, optical and electronic properties of such materials is of paramount interest for emergent technologies. Combination of liquid crystalline order and photoresponsive properties of the mesogens gave rise to the development of photochromic liquid crystals. One of the most exciting themes in this area is the light-driven self-assembly at the nanoscale. In this Review, we discuss recent advances in the field of photoswitchable liquid crystals with a focus on bend-shaped liquid crystals and photoswitchable dendrimers. Photoinduced phase transitions, photo-orientation and alignment, photo-mechanical and photo-rheological effects have been highlighted and discussed.
{"title":"Effects of photoswitching in complex partially ordered systems","authors":"A. Eremin","doi":"10.1080/21680396.2020.1867662","DOIUrl":"https://doi.org/10.1080/21680396.2020.1867662","url":null,"abstract":"In recent years, progress in optics and photonics stimulated the rapid development of multifunctional photoswitchable materials. The ability to manipulate the mechanical, optical and electronic properties of such materials is of paramount interest for emergent technologies. Combination of liquid crystalline order and photoresponsive properties of the mesogens gave rise to the development of photochromic liquid crystals. One of the most exciting themes in this area is the light-driven self-assembly at the nanoscale. In this Review, we discuss recent advances in the field of photoswitchable liquid crystals with a focus on bend-shaped liquid crystals and photoswitchable dendrimers. Photoinduced phase transitions, photo-orientation and alignment, photo-mechanical and photo-rheological effects have been highlighted and discussed.","PeriodicalId":18087,"journal":{"name":"Liquid Crystals Reviews","volume":"8 1","pages":"29 - 43"},"PeriodicalIF":5.1,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/21680396.2020.1867662","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45877442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-02DOI: 10.1080/21680396.2021.1904298
K. P. Zuhail, M. Humar, S. Dhara
We present a brief review on the effect of phase transitions on liquid crystal colloids. The paper focuses on the evolution of dipolar, quadrupolar and boojum colloids and the ensuing elastic distortions of the director field across phase transitions between various phases, including N, SmA, SmC and N*. The role of pre-transitional and post-transitional elasticity on the resulting defect structure is discussed. Our review includes the results of structural transitions of two-dimensional colloidal assemblies due to the transformation of the defects across the phase transitions. Finally, we discuss some future perspectives on further studies.
{"title":"Effect of phase transitions on liquid crystal colloids: a short review","authors":"K. P. Zuhail, M. Humar, S. Dhara","doi":"10.1080/21680396.2021.1904298","DOIUrl":"https://doi.org/10.1080/21680396.2021.1904298","url":null,"abstract":"We present a brief review on the effect of phase transitions on liquid crystal colloids. The paper focuses on the evolution of dipolar, quadrupolar and boojum colloids and the ensuing elastic distortions of the director field across phase transitions between various phases, including N, SmA, SmC and N*. The role of pre-transitional and post-transitional elasticity on the resulting defect structure is discussed. Our review includes the results of structural transitions of two-dimensional colloidal assemblies due to the transformation of the defects across the phase transitions. Finally, we discuss some future perspectives on further studies.","PeriodicalId":18087,"journal":{"name":"Liquid Crystals Reviews","volume":"8 1","pages":"44 - 57"},"PeriodicalIF":5.1,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/21680396.2021.1904298","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48635864","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-02DOI: 10.1080/21680396.2020.1734492
L. Gulrich
{"title":"Memoirs of my time at Kent State University during formation of the Liquid Crystal Institute","authors":"L. Gulrich","doi":"10.1080/21680396.2020.1734492","DOIUrl":"https://doi.org/10.1080/21680396.2020.1734492","url":null,"abstract":"","PeriodicalId":18087,"journal":{"name":"Liquid Crystals Reviews","volume":"8 1","pages":"1 - 4"},"PeriodicalIF":5.1,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/21680396.2020.1734492","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43838647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-02DOI: 10.1080/21680396.2020.1816861
Deepak Devadiga, T. N. Ahipa
Hydrogen bonding plays an important role in building the super-structures in chemical and biological systems because of its specificity and directionality. In this context, significant works have been conducted recently to study the role of hydrogen bonding interactions in the formation and/or stabilization of mesophases. Also, this flexible and active non-covalent interaction has been widely utilized in other fields such as self-assembly, crystal engineering, polymer chemistry and nanotechnology. However, hydrogen bond interactions have emerged in recent years as a tunable supramolecular synthetic method with adjustable phases and properties in the design of efficient liquid crystalline materials. The present critical review describes the preparation of various pyridine-based hetero-dimeric hydrogen-bonded mesogenic complexes, which were reported over the last 10 years and are mainly made of calamitic, bent, discotic and polymers. Also, it covers the structure, mesophase stability, role of various terminal/lateral substituents, and future perspectives of these complexes. GRAPHICAL ABSTRACT
{"title":"Heterodimeric hydrogen-bonded mesogens comprising pyridine moiety: a review","authors":"Deepak Devadiga, T. N. Ahipa","doi":"10.1080/21680396.2020.1816861","DOIUrl":"https://doi.org/10.1080/21680396.2020.1816861","url":null,"abstract":"Hydrogen bonding plays an important role in building the super-structures in chemical and biological systems because of its specificity and directionality. In this context, significant works have been conducted recently to study the role of hydrogen bonding interactions in the formation and/or stabilization of mesophases. Also, this flexible and active non-covalent interaction has been widely utilized in other fields such as self-assembly, crystal engineering, polymer chemistry and nanotechnology. However, hydrogen bond interactions have emerged in recent years as a tunable supramolecular synthetic method with adjustable phases and properties in the design of efficient liquid crystalline materials. The present critical review describes the preparation of various pyridine-based hetero-dimeric hydrogen-bonded mesogenic complexes, which were reported over the last 10 years and are mainly made of calamitic, bent, discotic and polymers. Also, it covers the structure, mesophase stability, role of various terminal/lateral substituents, and future perspectives of these complexes. GRAPHICAL ABSTRACT","PeriodicalId":18087,"journal":{"name":"Liquid Crystals Reviews","volume":"8 1","pages":"5 - 28"},"PeriodicalIF":5.1,"publicationDate":"2020-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/21680396.2020.1816861","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48389976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-01-01Epub Date: 2021-05-26DOI: 10.1080/21680396.2021.1919576
Oleg D Lavrentovich
The dynamics of small particles, both living such as swimming bacteria and inanimate, such as colloidal spheres, has fascinated scientists for centuries. If one could learn how to control and streamline their chaotic motion, that would open technological opportunities in the transformation of stored or environmental energy into systematic motion, with applications in micro-robotics, transport of matter, guided morphogenesis. This review presents an approach to command microscale dynamics by replacing an isotropic medium with a liquid crystal. Orientational order and associated properties, such as elasticity, surface anchoring, and bulk anisotropy, enable new dynamic effects, ranging from the appearance and propagation of particle-like solitary waves to self-locomotion of an active droplet. By using photoalignment, the liquid crystal can be patterned into predesigned structures. In the presence of the electric field, these patterns enable the transport of solid and fluid particles through nonlinear electrokinetics rooted in anisotropy of conductivity and permittivity. Director patterns command the dynamics of swimming bacteria, guiding their trajectories, polarity of swimming, and distribution in space. This guidance is of a higher level of complexity than a simple following of the director by rod-like microorganisms. Namely, the director gradients mediate hydrodynamic interactions of bacteria to produce an active force and collective polar modes of swimming. The patterned director could also be engraved in a liquid crystal elastomer. When an elastomer coating is activated by heat or light, these patterns produce a deterministic surface topography. The director gradients define an activation force that shapes the elastomer in a manner similar to the active stresses triggering flows in active nematics. The patterned elastomer substrates could be used to define the orientation of cells in living tissues. The liquid-crystal guidance holds a major promise in achieving the goal of commanding microscale active flows.
{"title":"Design of nematic liquid crystals to control microscale dynamics.","authors":"Oleg D Lavrentovich","doi":"10.1080/21680396.2021.1919576","DOIUrl":"10.1080/21680396.2021.1919576","url":null,"abstract":"<p><p>The dynamics of small particles, both living such as swimming bacteria and inanimate, such as colloidal spheres, has fascinated scientists for centuries. If one could learn how to control and streamline their chaotic motion, that would open technological opportunities in the transformation of stored or environmental energy into systematic motion, with applications in micro-robotics, transport of matter, guided morphogenesis. This review presents an approach to command microscale dynamics by replacing an isotropic medium with a liquid crystal. Orientational order and associated properties, such as elasticity, surface anchoring, and bulk anisotropy, enable new dynamic effects, ranging from the appearance and propagation of particle-like solitary waves to self-locomotion of an active droplet. By using photoalignment, the liquid crystal can be patterned into predesigned structures. In the presence of the electric field, these patterns enable the transport of solid and fluid particles through nonlinear electrokinetics rooted in anisotropy of conductivity and permittivity. Director patterns command the dynamics of swimming bacteria, guiding their trajectories, polarity of swimming, and distribution in space. This guidance is of a higher level of complexity than a simple following of the director by rod-like microorganisms. Namely, the director gradients mediate hydrodynamic interactions of bacteria to produce an active force and collective polar modes of swimming. The patterned director could also be engraved in a liquid crystal elastomer. When an elastomer coating is activated by heat or light, these patterns produce a deterministic surface topography. The director gradients define an activation force that shapes the elastomer in a manner similar to the active stresses triggering flows in active nematics. The patterned elastomer substrates could be used to define the orientation of cells in living tissues. The liquid-crystal guidance holds a major promise in achieving the goal of commanding microscale active flows.</p>","PeriodicalId":18087,"journal":{"name":"Liquid Crystals Reviews","volume":"8 2","pages":"59-129"},"PeriodicalIF":5.1,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/21680396.2021.1919576","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39852813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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