Gear trains have been used for centuries to translate
changes in gear rotational speed into changes in rotational force.
Cars, drills, and basically anything that has spinning parts use
them. Molecular-scale gears are a much more recent invention that
could use light or a chemical stimulus to initiate gear rotation.
Researchers at Nara Institute of Science and Technology (NAIST),
Japan, in partnership with research teams at University Paul
Sabatier, France, report in a new study published in Chemical
Science a means to visualize snapshots of an ultrasmall gear
train—an interconnected chain of gears—at work.