Surface Tension Rockets

At the human scale, surface tension is a force of little relevance compared to the force of gravity. However, at submillimeter scales, surface tension is a force to reckon with. Some organisms have found ways to use surface tension to achieve unexpected results. Basidiomycetes fungi, which include most edible mushrooms, use surface tension as an energy source to propel their spores into the air. The active process begins with the condensation of a water droplet at the base of the spore. The fusion of the droplet onto the spore creates a momentum that propels the spore forward (top).

A high-speed camera is used to make direct observations of the kinematics of the spore discharge in the fungus Auricularia auricula. This provided the input for the first detailed analysis of this unique discharge mechanism. This knowledge is being used to develop miniature rockets that are propelled over short distances solely by releasing surface tension energy (bottom).

Harvard MRSEC (DMR-0820484)