Toy Inventor’s Notebook: Make a Miraculous Marangoni Soap Boat

Here’s an update of a Victorian plaything. Cut out the fish on the dotted line and float it on a pan of water. Place a single drop of olive oil in the circle. The oil quickly spreads out the slit and across the water. The fish “swims” in the opposite direction, like an exhaust-spewing rocket subject to Newton’s third law of motion. Sadly, the soggy paper fish is only good for just a single use.

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