title: Geometrically unrestricted, topologically constrained control of liquid crystal defects using simultaneous holonomic magnetic and holographic optical manipulation.
abstract: Despite the recent progress in physical control and manipulation of various condensed matter, atomic, and particle systems, including individual atoms and photons, our ability to control topological defects remains limited. Recently, controlled generation, spatial translation, and stretching of topological point and line defects have been achieved using laser tweezers and liquid crystals as model defect-hosting systems. However, many modes of manipulation remain hindered by limitations inherent to optical trapping. To overcome some of these limitations, we integrate holographic optical tweezers with a magnetic manipulation system, which enables fully holonomic manipulation of defects by means of optically and magnetically controllable colloids used as "handles" to transfer forces and torques to various liquid crystal defects. These colloidal handles are magnetically rotated around determined axes and are optically translated along three-dimensional pathways while mechanically attached to defects, which, combined with inducing spatially localized nematic-isotropic phase transitions, allow for geometrically unrestricted control of defects, including previously unrealized modes of noncontact manipulation, such as the twisting of disclination clusters. These manipulation capabilities may allow for probing topological constraints and the nature of defects in unprecedented ways, providing the foundation for a tabletop laboratory to expand our understanding of the role defects play in fields ranging from subatomic particle physics to early-universe cosmology.
authors.affiliation: Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309, USA.
authors.forename: Michael C M
authors.initials: MC
authors.lastname: Varney
authors.affiliation: Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627, USA.
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: Jenness
authors.affiliation: Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309, USA and Department of Electrical, Computer, and Energy Engineering, Materials Science and Engineering Program, Liquid Crystals Materials Research Center, University of Colorado at Boulder, Boulder, Colorado 80309, USA and Renewable and Sustainable Energy Institute, National Renewable Energy Laboratory and University of Colorado at Boulder, Boulder, Colorado 80309, USA.
authors.forename: Ivan I
authors.initials: II
authors.lastname: Smalyukh
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D006696:Holography / Q000295:instrumentation* / Q000379:methods; D050866:Liquid Crystals / Q000737:chemistry* / Q000528:radiation effects*; D060526:Magnetic Fields; D059346:Magnets; D008422:Materials Testing / Q000379:methods; D008846:Micromanipulation / Q000295:instrumentation* / Q000379:methods; D052898:Optical Tweezers; D011829:Radiation Dosage; D013314:Stress, Mechanical