Whispering gallery mode lasers for sensing force in biological systems

  • Joseph Samuel Hill

Student thesis: Doctoral Thesis (PhD)

Abstract

The burgeoning field of mechanobiology has given rise to many new discoveries in recent years. There has been an expansion in the devices created to measure the nanoscopic forces cells and developing organisms use to interact with their surroundings. Whispering gallery mode (WGM) lasers have also been an expanding area of research recently because of the excellent laser characteristics they can provide at microscopic scales.

This study investigates the use of microscopic deformable WGM droplet lasers as a probe for force sensing in biological systems. A complete fabrication and analysis method is demonstrated showing that droplet microlasers are a tool that can be implemented in many biological systems. Droplet microlasers are used as an intracellular and extracellular force sensor. Further, the droplet microlasers are used to measure in vivo forces within Drosophila melanogaster larvae. The analysis protocol models the splitting of non-degenerate laser modes to determine the geometry of a deformed droplet microlaser. Combining the geometry and mechanical properties of the droplet microlaser allows an applied force to be inferred.

The droplet microlasers developed can measure forces within single cells showing a clear difference in force between interactive and non-interactive cells. As an extracellular sensor, the droplet microlasers measured the response time of the force rat aortic smooth muscle cells (RASMCs) applied to their extracellular matrix when a drug (sodium nitroprusside) is applied. The magnitude of the forces sensed by the droplet microlasers can be adjusted by tuning its mechanical properties. Forces between 250 pN to 7 nN were measured. Further, it is demonstrated that the droplet microlasers can sense deeper than any other light-based force sensor, recording measurements at 300 μm deep within a 3rd instar Drosophila melanogaster larva at an acquisition rate of 10 Hz.
Date of Award12 Jun 2023
Original languageEnglish
Awarding Institution
  • University of St Andrews
SupervisorMalte Christian Gather (Supervisor)

Keywords

  • Microlaser
  • Deformable laser
  • Droplet laser
  • Micro-force sensor
  • Mechanical sensor
  • Whispering gallery mode laser

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