Scaling rules for flow focusing devices: From standard to large FFDs for cell encapsulation in alginates

Flow focusing devices (FFDs), with dimensions smaller than 100 mum have recently been used for cell encapsulation. However, encapsulation of larger clusters of cells, like islets of Langerhans, is of considerable interest. Producing larger capsules requires larger FFDs. We focus here on the geometrical scaling-up between a small FFD (50 mum) and a larger one (100 mum, 200 mum, 1 mm). We determine the driving pressure conditions to obtain the droplet regime at any size of the FFD. A similar behavior of the device is experimentally obtained by a scaling of the dimensions by a ratio lambda and a scaling of the driving pressures by the ratio 1/lambda.