Temperature dependent stiffness and visco-elastic behaviour of lipid coated microbubbles using atomic force microscopy

Abstract

The compression stiffness of a phospholipid microbubble was determined using force-spectroscopy as a function of temperature. The stiffness was found to decrease by approximately a factor of three from ∼0.08 N m⁻¹, at 10 °C, down to ∼0.03 N m⁻¹ at 37 °C. This temperature dependence indicates that the surface tension of lipid coating is the dominant contribution to the microbubble stiffness. The time-dependent material properties, e.g. creep, increased non-linearly with temperature, showing a factor of two increase in creep-displacement, from ∼24 nm, at 10 °C, to 50 nm, at 37 °C. The standard linear solid model was used to extract the visco-elastic parameters and their determination at different temperatures allowed the first determination of the activation energy for creep, for a microbubble, to be determined.