Channel deformations during elastocapillary spreading of gaseous embolisms in biomimetic leaves

The nucleation and/or spreading of bubbles in water under tension (due to water evaporation) can be problematic for most plants along the ascending sap network-from roots to leaves-called xylem. Due to global warming, trees facing drought conditions are particularly threatened by the formation of such embolisms, which hinders sap flow and can ultimately be fatal. Polydimethylsiloxane (PDMS)-based biomimetic leaves simulating evapotranspiration have demonstrated that, in a linear configuration, the existence of a slender constriction in the channel allows for the creation of intermittent embolism propagation (as an interaction between the elasticity of the biomimetic leaf and the capillary forces at the air/water interfaces) (Keiser et al. 2022 J. Fluid Mech. 948, A52 (doi:10.1017/jfm.2022.733); Keiser et al. 2024 J. R. Soc. Interface 21, 20240103 (doi:10.1098/rsif.2024.0103)). Here, we use analogue PDMS-based biomimetic leaves in one dimension and two dimensions. To better explore the embolism spreading mechanism, we add to the setup an additional technique, allowing to measure directly the microchannel's ceiling deformation versus time, which corresponds to the pressure variations. We present here such a method that allows one to have quantitative insights into the dynamics of embolism spreading. The coupling between channel deformations and the Laplace pressure threshold explains the observed elastocapillary dynamics.