  It is well recognized that the miniaturization of electromechanical devices
will bring a revolution to humanity in the coming decades synonymous with the
effects of miniaturizing electronic devices in those previous. An
electromechanical actuator - a device that converts electrical energy to
mechanical deformation or motion - is the core component of many such devices.
Consequently, research interrogating mili-, micro-, and nano-actuation has, and
will continue to become increasingly essential. The challenge is that behaviour
of actuators at small size scales vastly differs to those at the macroscale. We
cannot simply shrink the size of conventional actuators at the macroscale down
to the micro/nanoscale. In addition, conventional actuation materials (such as
piezoelectric ceramics and shape memory alloys) have poor properties and
performances when fabricated at a small length scale. There is an urgent need
to discover novel actuation materials at small length scale. This paper will
review recent advances in graphene-based actuation materials. We will focus on
different actuation physical mechanisms of this most well-known two-dimension
material. The in-depth physical understanding and insights will lay the ground
for further optimization/development of graphene-based actuators. They may also
provide valuable knowledge for the design and development of other
two-dimensional actuation materials and actuators.
