  Future brain-machine interfaces, prosthetics, and intelligent soft robotics
will require integrating artificial neuromorphic devices with biological
systems. Due to their poor biocompatibility, circuit complexity, low energy
efficiency, and operating principles fundamentally different from the ion
signal modulation of biology, traditional Silicon-based neuromorphic
implementations have limited bio-integration potential. Here, we report the
first organic electrochemical neurons (OECNs) with ion-modulated spiking, based
on allprinted complementary organic electrochemical transistors. We demonstrate
facile biointegration of OECNs with Venus Flytrap (Dionaea muscipula) to induce
lobe closure upon input stimuli. The OECNs can also be integrated with
all-printed organic electrochemical synapses (OECSs), exhibiting short-term
plasticity with paired-pulse facilitation and longterm plasticity with
retention >1000 s, facilitating Hebbian learning. These soft and flexible OECNs
operate below 0.6 V and respond to multiple stimuli, defining a new vista for
localized artificial neuronal systems possible to integrate with bio-signaling
systems of plants, invertebrates, and vertebrates.
