Generally, water repellent objects and those that attract or absorb water have very different microscopic-level attributes that endow them with their behavior. For example, the myriad tiny hairs on a gecko’s body help it to efficiently repel water, whilst specially treated cotton designed for harvesting water from the air contains millions of tiny pores that draw in liquid. Now researchers have discovered a way to use a single type of material to perform both functions, switching between liquid attraction and liquid repulsion, simply through the application of an electric voltage.
To change the amount of stiction, a nanoscale mesh made of a single layer of boron nitride (or “white graphene”, as it is sometimes known) was grown on a bed of rhodium, to create a honeycomb structure with comb depths of around 0.1 nanometers and comb to comb distance of 3.2 nm. When a voltage is applied to the structure, the mesh flattens out, changing the contact angle between the water droplets and the molecules so greatly that surface tension can no longer be maintained, and the droplets lose their grip on the surface.
The researchers see uses for this type of electrically-controlled behavior in biology, where this effect could enable control and handling of cells at the microscopic level, which may be useful in creating new and complex artificial multi-cellular arrangements that could help bolster scientific research. They also see the effect as the basis for technologies to create micro-capillary pumps, where the pressure and flow are controlled simply by the application of electricity along the length of a nanoscale tube.
The results of this research were recently published in the journal Nature.
Source: http://www.gizmag.com/
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