  Magnetic fluids are excellent candidates for important research fields
including energy harvesting, biomedical applications, soft robotics and
exploration. However, notwithstanding relevant advancements such as shape
reconfigurability, that have been demonstrated, there is no evidence for their
computation capability, including the emulation of synaptic functions. Here, we
experimentally demonstrate that a Fe3O4 water-based Ferrofluid (FF) can perform
electrical analog computing and be programmed using quasi DC signals and read
at Radio Frequency (RF) mode. We have observed features in all respects
attributable to a memristive behavior, featuring both short and long-term
information storage capacity and plasticity. The colloid was capable of
classifying digits of a 8x8 pixel dataset using a custom in-memory signal
processing scheme, and through Physical Reservoir Computing (PRC) by training a
readout layer.
