Ecology reaches new heights, oil is being replaced by bacteria

Jul 13, 2015 10:11 GMT  ·  By

US-based researchers have built evaporation-driven engines that can power common tasks like locomotion and electricity generation using biologically inspired artificial muscles which respond to humidity fluctuations.

By exploiting spatial gradients found near evaporating surfaces that are related to the level of humidity, and confining water in specially designed hydroscopic materials, it's quite possible to convert energy from evaporation to mechanical work. In response to changing relative humidity, the confinement will induce large pressure levels that can lead to locomotion.

To better control evaporation rates, the researchers modified natural bacteria and created the hygroscopy-driven artificial muscles, or HYDRA muscles, that react quickly to hydration-driven actuation. This scenario occurs because of the elastic features of these modified bacteria muscles that expand rapidly when in contact with humidity.

The elastic material is made from plastic tape coated with a micrometer thick bacteria spore layer formed out of a modified Bacillus subtilis, without their outer protein protective layers. The plastic tape will curve once filled with water while in full humidity levels, and when exiting the encased humid area, gravity will straighten them in dry conditions. The bacteria-covered tapes are so strong that they can lift their weight in dry conditions.

As a result, the research team created two oscillatory and rotary evaporation-driven engines to prove their concept, and yes they run entirely autonomously when placed at air-water interfaces. The engines were able to light up LEDs through an electricity generator and drive a small car.

Evaporation engines may find new and experimental applications in powering things like robotics, sensors and other devices that work in the natural environment, and their immense potential comes from the fact that the material is cheap and the spores are naturally occurring.