3D Printing of a Swellable Material
The video treats about sodium polucarbonate ‎(C3H3NaO2) this is a superabsorbent polymer has the ability to absorb as much as 100 to 1000 times its mass in water. This is used as desiccant on products that moisture can be a problem basically during storage prior selling. The video shows the water how is trapped inside the particles of sodium polycarbonate, this happens inside a diaper or any product urine odor absorbing, also is used on waste liquid control. 

Also you can find something similar on some products that has a little bag that says silica gel (SiO2).