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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).
Movie: http://www.mrsec.harvard.edu/200x64.avi.
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). |