Fig. 3: Shape modes and jet formation of single microbubbles in contact with a PEG substrate.
From: Cyclic jetting enables microbubble-mediated drug delivery
a–f, Shape modes with angular wavenumbers l ranging from 1 to 6. The top panels display the bright-field snapshots from two consecutive ultrasound cycles, at a generic time instant t = ti and one ultrasound (US) period TUS = 1 μs later, at t = ti + TUS. These images illustrate the cyclic transition between a geometric pattern and its dual during the shape mode oscillation. Odd-wavenumber shape mode patterns are self-dual. The red dashed sketches show the polyhedral representation of shape mode patterns. The bottom panels show the combination of spherical harmonics \({Y}_{l}^{\,m}\) representing the shape mode patterns. The red regions denote outward deformation, whereas the blue regions indicate inward deformation. g, Experimentally observed shape modes with angular wavenumber l as a function of the equilibrium bubble radius. The uncertainty in the bubble radius measurement corresponds to half the pixel size (80 nm). h–k, Jets driven by shape modes with angular wavenumbers l ranging from 1 to 4. The top panels show the bright-field images depicting the jets generated by the shape pattern or by its dual. The bottom panels show the bubble-shape decomposition in the breathing mode (spherical oscillation) and shape mode. The red regions denote outward deformation, whereas the blue regions indicate inward deformation. Jets manifest during compression phases in the sunken regions of the shape mode. Sub., substrate.
