Temperature dependence of acoustic properties of natural snail mucus by Brillouin spectroscopy

Hanlon, Dillon (2020) Temperature dependence of acoustic properties of natural snail mucus by Brillouin spectroscopy. Masters thesis, Memorial University of Newfoundland.

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Abstract

Brillouin light scattering was used to understand how the acoustic and mechanical properties of gastropod mucus are influenced by temperature over the temperature range -11ᴼC ≤ T ≤ 52ᴼC. Two peaks were observed in spectra obtained in this study, one which was present throughout the full temperature range and at a frequency shirt of ~8.0 GHz, while the other peak appeared at a shift of ~18.5 GHZ but only for temperatures below ~ -3.0ᴼC. Results for the 8.0 GHz liquid mucus peak showed minor changes in both frequency shift and FWHM for temperatures greater than -2.5ᴼC. As well, the intensity of this peak showed an overall increase as temperature increases. For temperatures below -2.5ᴼC, the sound velocity for the mucus mode sh owed an overall increase as temperature decreased, with a difference of ~11% between the sound velocity at T = -3.0ᴼC (1550 m/s) and -11.0ᴼC (1750 m/s). Moreover, the liquid mucus bulk modulus was also obtained and also shows an overall increase as temperature decreases in this temperature regime. Additionally, this 8.0 GHz peak also revealed an exponential decrease in the FWHM as temperature increased with linewidth ranging from 12 GHz to 0.6 GHz for temperatures T = 11.0ᴼC and 52.0ᴼC respectively. Likewise, sound absorption values were also obtained in this study and showed an exponential decrease as temperature increased with values ranging from ~ 120 X 10⁻¹⁵ s²/m to ~15 X 10⁻¹⁵ s²/m over the temperature range -11.0ᴼC ≤ T ≤ 52ᴼC for all samples. From the sound absorption, the interaction energy between the molecules in the mucus was obtained and showed a large change in its values for temperatures above and below T = 2.5ᴼC. The second peak occurring at ~18.5 GHz deemed due to ice Ih showed very small changes in frequency and linewidth as temperature decreases, as well it was seen that as the temperature decreased the intensity of this peak generally increased. The sound velocity for this mode increases slightly as temperature decreases with values ranging from 3800 to 3860 m/s for temperatures T = -3.0ᴼC and T = -11.0ᴼC respectively. Likewise, the bulk modulus of the ice slightly increases in this temperature regime. Collectively, the results from this work suggest a phase transition between a viscous liquid state to a mixed solid-liquid state. Comparison of the results obtained in this study is made to similar liquid systems (i.e., water, water and polymer mixtures).

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