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dc.contributor.authorKatsamba, Panayiota
dc.date.accessioned2018-10-02T15:03:51Z
dc.date.available2018-10-02T15:03:51Z
dc.date.issued2018-10-20
dc.date.submitted2018-06-14
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/283006
dc.description.abstractA prevalent morphology in the microscopic world of artificial microswimmers, bacteria and viruses is that of a helix. The intriguingly different physics at play at the small scale level make it necessary for bacteria to employ swimming strategies different from our everyday experience, such as the rotation of a helical filament. Bio-inspired microswimmers that mimic bacterial locomotion achieve propulsion at the microscale level using magnetically actuated, rotating helical filaments. A promising application of these artificial microswimmers is in non-invasive medicine, for drug delivery to tumours or microsurgery. Two crucial features need to be addressed in the design of microswimmers. First, the ability to selectively control large ensembles and second, the adaptivity to move through complex conduit geometries, such as the constrictions and curves of the tortuous tumour microvasculature. In this dissertation, a mechanics-based selective control mechanism for magnetic microswimmers is proposed, and a model and simulation of an elastic helix passing through a constricted microchannel are developed. Thereafter, a theoretical framework is developed for the propulsion by stiff elastic filaments in viscous fluids. In order to address this fluid-structure problem, a pertubative, asymptotic, elastohydrodynamic approach is used to characterise the deformation that arises from and in turn affects the motion. This framework is applied to the helical filaments of bacteria and magnetically actuated microswimmers. The dissertation then turns to the sub-bacterial scale of bacteriophage viruses, ‘phages’ for short, that infect bacteria by ejecting their genetic material and replicating inside their host. The valuable insight that phages can offer in our fight against pathogenic bacteria and the possibility of phage therapy as an alternative to antibiotics, are of paramount importance to tackle antibiotics resistance. In contrast to typical phages, flagellotropic phages first attach to bacterial flagella, and have the striking ability to reach the cell body for infection, despite their lack of independent motion. The last part of the dissertation develops the first theoretical model for the nut-and-bolt mechanism (proposed by Berg and Anderson in 1973). A nut being rotated will move along a bolt. Similarly, a phage wraps itself around a flagellum possessing helical grooves, and exploits the rotation of the flagellum in order to passively travel along and towards the cell body, according to this mechanism. The predictions from the model agree with experimental observations with respect to directionality, speed and the requirements for succesful translocation.
dc.description.sponsorshipThis work was funded by the EPSRC (3 years) and the last year was funded by Prof Eric Lauga's grant from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement 682754 to Prof Eric Lauga).
dc.language.isoen
dc.rightsAll rights reserved
dc.rightsAll Rights Reserveden
dc.rights.urihttps://www.rioxx.net/licenses/all-rights-reserved/en
dc.subjecthelix
dc.subjectbacteria
dc.subjectvirus
dc.subjectphage
dc.subjectbacteriophage
dc.subjectmicroswimmer
dc.subjectfilament
dc.subjectslender
dc.subjectselective control
dc.subjectmagnetic actuation
dc.subjectpropulsion
dc.subjectapplication-driven design
dc.subjectelasticity
dc.subjectelastohydrodynamics
dc.subjectfluid-structure interaction
dc.subjectconstriction
dc.subjectcomplex conduit
dc.subjectadaptive design
dc.subjectdeformation
dc.subjectnut-and-bolt mechanism
dc.subjectflagellotropic
dc.subjectflagellum
dc.subjectbacterium
dc.subjecttranslocation
dc.subjectmicroscale
dc.subjectfluid mechanics
dc.subjectartificial-microswimmer
dc.subjectdeformation feedback to kinematics
dc.subjectswimming
dc.subjectdevice
dc.subjecttargeted-drug delivery
dc.subjectmicrofluidics
dc.subjectmicromanipulation
dc.subjectminimally-invasive medical applications
dc.subjectbiophysics
dc.subjectmechanics
dc.subjectbiomechanics
dc.titleBiophysics of Helices: Devices, Bacteria and Viruses
dc.typeThesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnameDoctor of Philosophy (PhD)
dc.publisher.institutionUniversity of Cambridge
dc.publisher.departmentDepartment of Applied Mathematics and Theoretical Physics (DAMTP)
dc.date.updated2018-09-22T01:29:08Z
dc.identifier.doi10.17863/CAM.30371
dc.contributor.orcidKatsamba, Panayiota [0000-0001-6328-3018]
dc.publisher.collegeNewnham
dc.type.qualificationtitlePhD in Applied Maths and TP
cam.supervisorLauga, Eric
cam.supervisor.orcidLauga, Eric [0000-0002-8916-2545]
cam.thesis.fundingtrue
rioxxterms.freetoread.startdate2019-10-02


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