Droplets of simple liquids, like oil and water, are essential engineering systems.  Classically, we use them to deliver material, transport heat, and control chemical reactions. Thanks to microfluidic technology, a wealth of new applications has emerged in recent years. 

Evolution, however, beat us to it. For more than a billion years, living cells have been producing microscopic droplets in the cytoplasm.  These droplets have very different chemical compositions and mechanical properties than the simple fluids we encounter daily.  Their primary job is thought to be the organization of chemical reactions.  However, they can also play a mechanical role, as the cohesive forces that hold droplets together inevitably lead to adhesion.  I will demonstrate this with the interaction of stress granules and the cytoskeleton in human epithelial cells. 

This broad class of micro-fluids has great engineering potential.  I will show how enzymatic activity can transform a simple droplet into a micro-robot.  These ‘drobots’ already have rudimentary capabilities of sensing and actuation, fueled by energy harvested from their surroundings.   On the horizon, enzymatic networks will enable programmability and control.