The possibility of turning sketches into real-life objects was never really accomplished by the substitution of desktop 3D printers with hand-held 3D-printing pens. The reason is that these 3D-printing pens are not as magnanimous as this 3D Foam Pen that swaps melted plastic for soap suds.
This foam pen costs $42 and is very safe as compared to 3D-printing pens which needs to heat up to melt the plastic they eject. There is no risk like getting burns (which you might get while using a hot glue gun) in this case as this foam pen produces 3D shapes via the consumption of same foaming liquid hand soap that you use for washing your hands.
Manual pumping is also not necessary in using this pen. The pen automatically froths the liquid soap inside it into foam. All you have to do is press a single button to eject it from a nozzle. You also need not to worry about cleaning up a mess afterwards. As the pen squeezes out soap whenever it is used, hence, it is already halfway cleaned.
Watch the following video and see how fast the Japanese girls master 3D Foam Pen.