Abstract
(June 16, 2015) Evaporation is a ubiquitous phenomenon in
the natural environment and a dominant form of energy transfer in the Earth’s
climate. Engineered systems rarely, if ever, use evaporation as a source of
energy, despite myriad examples of such adaptations in the biological world.
Here, we report evaporation-driven engines that can power common tasks like
locomotion and electricity generation. These engines start and run autonomously
when placed at air–water interfaces. They generate rotary and piston-like
linear motion using specially designed, biologically based artificial muscles
responsive to moisture fluctuations. Using these engines, we demonstrate an
electricity generator that rests on water while harvesting its evaporation to
power a light source, and a miniature car (weighing 0.1 kg) that moves forward
as the water in the car evaporates. Evaporation-driven engines may find
applications in powering robotic systems, sensors, devices and machinery that
function in the natural environment.