Cell decision making at a microfluidic fork

Many cell types, such as white blood cells, undergo directed migration during wound healing, development and immune response. A simple paradigm for this is related to the aphorism attributed to Yogi Berra "When you come to a fork, take it” - so that one can ask what happens when an active cell comes to a junction in a vasculature? Since the paths may have different mechanical resistance and/or chemokine concentrations, how does the cell respond by integrating multiple signals across different spatial-temporal scales and reject transient noise? We use a combination of numerical simulations and microfluidic experiments to understand the mechanochemistry of cellular decision-making at a confined bifurcation junction. The cell is modelled as a deformable, active acto-myosin cortex surrounding a fluid volume, with active stresses which are a function of the local hydrodynamic and chemical cues. We show how the system shows a range of phenomena reminiscent of critical slowing down, and noise-induced tipping, and compare the results with experiments on single cells moving through a confined microfluidic fork.