RESEARCHERS at the Massachusetts Institute of Technology have found a way to grow submicroscopic wires in water with great precision, making it possible to produce entire electronic devices through a liquid-based process.
The research team demonstrated the hydrothermal synthesis technique by producing a functional light-emitting diode (LED) array made of zinc oxide nanowires in a microfluidic channel.
This was done on a lab bench under relatively benign conditions: essentially using a syringe to push solution through a capillary tube one-tenth of a millimeter wide, without expensive semiconductor manufacturing processes and facilities.
The nanomaterials’ different shapes can lead to dramatic differences in behaviour.
According to the researchers, for nanostructures, there is a coupling between the geometry and the electrical and optical properties. By tuning the geometry, it is possible to tune the functional properties.
The system can precisely control the aspect ratio (the ratio of length to width) of the nanowires to produce anything from flat plates to long, thin wires.
While there are existing ways to control the morphology of wires, these have mostly required much higher temperatures or organic solvents. Being able to do so in water under low-temperature conditions makes it easier to manufacture the devices on flexible polymers and plastics.
The key to controlling the shapes of the nanostructures was found to be the electrostatic properties of the zinc oxide material as it grows from a solution. The ions of different compounds, when added to the solution, attach themselves electrostatically only to certain parts of the wire, inhibiting the wire’s growth in those directions. The amount of inhibition depends on the specific properties of the added compounds.
While this work was done with zinc oxide nanowires the MIT scientists believe the method they developed for controlling the shape of the wires can be expanded to different material systems such as titanium dioxide, which is being investigated for devices such as solar cells.
Growing electronic devices underwater Electronics News
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