On the use of evanescent fields to investigate nanoscale phenomena - from optical forces to cellular processes.

  • Witek K Szeremeta

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

Nanoscale is a special regime where the convergence of natural sciences occurs. Developing versatile tools to investigate phenomena on that scale is crucial for understanding intricate mechanisms which have consequences on macroscale.
This work shows the development of the new generation of Lateral Molecular Force Microscope (LMFM) and in particular the design of a new Vertical Positioning System for vertically oriented micro-cantilevers as well as a method for adjusting their tilt angle. The vertical orientation of the mechanical sensor allows it to have much lower stiffness (compared to that of a conventional Atomic Force Microscope), giving access to femtonewton and sub-femtonewton force resolution.
The unidirectional bending of the silicon nitride cantilevers entering the evanescent field is investigated and identified as an effect triggered by light coupling inside the cantilever. In relation to this bias bending, photostriction effect has been identified as the most likely mechanism behind it.
This works presents a range of optical forces measured in an evanescent field. In particular, a new experimental procedure is implemented to directly measure the transverse Belinfante spin momentum. The new experimental results give an additional insight into the fact, that the transfer of the helicity-dependent momentum to the micro-cantilever is a surface effect.
Finally, the LMFM setup is used to develop and establish the Sub-Cellular Fluctuation Imaging method. Scattering from the sub-cellular components of a bacterium under evanescent field illumination is utilised to assess its metabolic state, opening up the possibility of a label-free rapid Antimicrobial Susceptibility Tests.
Date of Award23 Mar 2021
Original languageEnglish
Awarding Institution
  • University of Bristol
SupervisorMassimo Antognozzi (Supervisor) & Mervyn J Miles (Supervisor)

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