NANOCOMPOSITES
Flexible devices are produced by printing electronic circuits on soft
materials such as foils, plastics or polymers. They are lightweight and
can fold or bend without affecting the functioning of the electronics. They are
fast gaining attention for their broad application potential. Wearable devices
such as activity trackers are a typical example.
In recent times, Graphene-based nanocomposites are
increasingly being explored to enhance the durability and toughness of flexible
electronics. However, a primary challenge arises in establishing electronic
properties of materials, since nanomaterials behave differently to the flow
of electrons in the circuit.
In a preliminary study, researchers from Chennai-based SRM
Institute of Science and Technology have demonstrated the electronic properties
of a nanocomposite made from graphene and Polyvinylidene Fluoride. The polymer
provides flexibility while grapheme enhances electrical properties.
When analysed with a Scanning Tunnelling Microscope, the
movement of electrons across the potential barriers were seen, indicating that
the nanocomposite
had
tunnelling properties in the Coulomb blockade region.
Coulomb blockade
is a phenomenon observed especially in nanoscale materials. In a regular
conducting material, there is free flow of conduction electrons. But this is
not so in nanospaces, where conducting electrons form a cloud of strong
repulsive forces preventing other electrons from adjacent molecules from
flowing freely, and the device no longer follows the Ohm’s law.
Another significant challenge arising with nanocomposites is
their reproducibility. The research
team overcame this by employing fabrication technique called melt-mixing
and casting.
For a nanocomposite to be used effectively in electronics,
it has to overcome the non-linear response of current-voltage behaviour,
suitably exhibit dielectric and charge storage, withstand high potential and
facilitate the conduction of electrons for an on-off mode operation for
nano-switching in electronic devices.
To achieve these parameters, defect-oriented quasi grapheme was
employed; that is, a few carbon bonds in the graphene material were
deliberately left unfinished, which led to the effective transfer of electrons
across the electrostatic barrier
Breakdown tests revealed that the nanocomposite could withstand
high voltages. This means it could work over a broad range of
voltage applications without electrical breakdowns.
