Droplet release and fragmentation of onion cutting

Cutting onions in kitchen often results in tear induction due to the generation and advection of pungent aerosols. In this talk, we explore the correlations between onion tissue straining and the droplet ejection mechanisms during a cutting sequence under various onion-blade features and interactions. Complexity of droplets ejection in onions originates in the soft mesophyll tissues, effectively functioning as a collection of pressurized elastic capsules, sandwiched by tough epidermal skins, allowing for localized stress concentration before skin rupture. We extract the size and speed (up to 30 m/s) distribution of droplets ejecting from fractured onion surface for different blade thicknesses, cutting speeds, and onion orientations. We applied Digital Image Correlation to reveal the 2D stress map of the transverse plane upon indentation, rupture, and steady-state cutting. We further developed direct pressure probing methodology to determine the tissue pressure during cutting. The current study helps establish connections between contact mechanics of pressurized elastic composites and fluid physics of droplet fragmentations, specifically revealing insights on the "tearless" cutting techniques for onions.