  Neuromorphic computing devices attempt to emulate features of biological
nervous systems through mimicking the properties of synapses, towards
implementing the emergent properties of their counterparts, such as learning.
Inspired by recent advances in the utilisation of liquid marbles (microlitre
quantities of fluid coated in hydrophobic powder) for the creation of
unconventional computing devices, we describe the development of liquid marbles
with neuromorphic properties through the use of copper coatings and 1.0 mg/ml
carbon nanotube-containing fluid cores. Experimentation was performed through
sandwiching the marbles between two cup-style electrodes and stimulating them
with repeated DC pulses at 3.0 V. Our results demonstrate that `entrainment' of
a carbon nanotube filled-copper liquid marble via periodic pulses can cause
their electrical resistance to rapidly switch between high to low resistance
profiles, upon inverting the polarity of stimulation: the reduction in
resistance between high and low profiles was approximately 88\% after two
rounds of entrainment. This effect was found to be reversible through reversion
to the original stimulus polarity and was strengthened by repeated
experimentation, as evidenced by a mean reduction in time to switching onset of
43\%. These effects were not replicated in nanotube solutions not bound inside
liquid marbles. Our electrical characterisation also reveals that
nanotube-filled liquid marbles exhibit pinched loop hysteresis IV profiles
consistent with the description of memristors. We conclude by discussing the
applications of this technology to the development of unconventional computing
devices and the study of emergent characteristics in biological neural tissue.
