Jumping droplets key to energy efficient products

Microscopic water droplets jumping from one surface to another could hold the key to a wide array of more energy efficient products — from large solar panels to compact laptop computers, say scientists.

A team at Duke University has, in fact, developed a new way of producing thermal diodes, devices which regulate heat to preferentially flow in a certain direction, effectively creating a thermal conductor in the forward direction and an insulator in the reverse direction.

While thermal diodes can be made from solid materials, these solid-state diodes are not nearly as effective as “phase-change” thermal diodes that rely on vaporisation and condensation to transport heat, say the scientists.

These phase-change diodes can transfer over a hundred times more heat in the forward direction compared to the reverse, but with major limitations — they are dependent on gravity or restricted by a tubular configuration.

These limitations severely constrain the application of phase-change thermal diodes, for example, in mobile electronics which require orientation independence or solar panels which require a large surface area.

The Duke engineers believe they have figured out a way  to solve these limitations to existing thermal diodes by exploiting self-propelled water droplets, which can jump from a superhydrophobic (highly water-repellent) surface to a superhydrophilic (highly absorbent) surface, but not the other way around.