Ultrasonic agitation for surface plasmon resonance biosensors

  • Hannah Johnston

Student thesis: Doctoral ThesisDoctor of Philosophy


Due to their biocompatibility and ability to yield a localised surface plasmon resonance, surface-based nanoparticles have gained popularity in various biosensing applications. In such configurations, fluid containing biological material such as proteins is injected into a static cell containing the sensing surface. Without sonication, the injected fluid remains static, and the rate of the biological material binding to the nanoparticle is diffusion limited. As a consequence, mixing is slow, particularly for large molecules. Acoustic streaming has been proposed as a solution to overcome the limitation of mixing in surface based biosensing devices.

This thesis reviews the effects of integrating ultrasonic technology into surface-based biosensors. The acoustic-structure interaction between acoustic pressure fields and nanoparticles is of particular interest, as any deviation in size or shape of the nanoparticle can have repercussions for its ability to yield a localised surface plasmon resonance at a specific optical wavelength. To probe this interaction, simulations were used in tandem with experimental evaluation techniques, exposing the nanoparticles to high frequency, 2 MHz, radiation to assess the deformations caused to nanoparticles under large acoustic pressure fields. Furthermore, experimentally exposing the nanoparticles to lower frequency acoustic radiation, 20 kHz, allowed analysis of their ability to act as nucleation sites for acoustic cavitation events, which has many interesting applications. Appraisal of the efficiency with which the acoustic streaming interaction and acoustic radiation force could be harnessed to encourage protein migration to a sensing surface was also examined using computational simulation and presented here.

Finally, the design and prototyping of ultrasonic devices that are easily integrable into biosensors is included. Ultrasonic transducers were created with resonance frequencies around 2 MHz so to encourage acoustic streaming events in the biosensing cells. The acoustic streaming is the stimulus driving biological cells toward nanostructured sensing surfaces. Piezoelectric materials, fabrication, characterisation methods and possible applications are discussed. The behaviour and performance of the devices was investigated and predicted using virtual prototyping with computer simulations and these are verified experimentally. Issues associated during the development are highlighted and discussed. To assist long term practical adoption, guidance for further experimentation and characterisation is also addressed.
Date of AwardDec 2020
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SponsorsEngineering & Physical Sciences Research Council
SupervisorRobert Pollard (Supervisor) & Sandy Cochran (Supervisor)

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