For the first time, researchers demonstrate an artificial organic neuron, a
nerve cell, that can be integrated with a living plant and an artificial
organic synapse. Both the neuron and the synapse are made from printed organic
electrochemical transistors.
On connecting to the carnivorous Venus flytrap, the electrical pulses from
the artificial nerve cell can cause the plant's leaves to close, although no
fly has entered the trap. Organic semiconductors can conduct both electrons
and ions, thus helping mimic the ion-based mechanism of pulse (action
potential) generation in plants. In this case, the small electric pulse of
less than 0.6 V can induce action potentials in the plant, which in turn
causes the leaves to close.
"We chose the Venus flytrap so we could clearly show how we can steer the
biological system with the artificial organic system and get them to
communicate in the same language," says Simone Fabiano, associate professor
and principal investigator in organic nanoelectronics at the Laboratory of
Organic Electronics, Linköping University, Campus Norrköping.
In 2018 the research group at Linköping University became the first to
develop complementary and printable organic electrochemical circuits -- that
is, with both n-type and p-type polymers, which conduct negative and
positive charges. This made it possible to build printed complementary
organic electrochemical transistors. The group has subsequently optimised
the organic transistors, so that they can be manufactured in printing
presses on thin plastic foil. Thousands of transistors can be printed on a
single plastic substrate. Together with researchers in Lund and Gothenburg,
the group has used the printed transistors to emulate the neurons and
synapses of the biological system. The results have been published in the
journal Nature Communications.
"For the first time, we're using the transistor's ability to switch based on
ion concentration to modulate the spiking frequency," says Padinhare
Cholakkal Harikesh, post-doctoral researcher at the Laboratory of Organic
Electronics. The spiking frequency gives the signal that causes the
biological system to react.
"We've also shown that the connection between the neuron and the synapse has
a learning behaviour, called Hebbian learning. Information is stored in the
synapse, which makes the signalling more and more effective," says Simone
Fabiano.
The hope is that artificial nerve cells can be used for sensitive human
prostheses, implantable systems for relieving neurological diseases, and
soft intelligent robotics.
"We've developed ion-based neurons, similar to our own, that can be
connected to biological systems. Organic semiconductors have numerous
advantages -- they're biocompatible, biodegradable, soft and formable. They
only require low voltage to operate, which is completely harmless to both
plants and vertebrates" explains Chi-Yuan Yang, post-doctoral researcher at
the Laboratory of Organic Electronics.
The research has been financially supported by the Knut and Alice Wallenberg
foundation, the Swedish Research Council, the Swedish Foundation for
Strategic Research and the Swedish Government Strategic Research Area in
Materials Science on Functional Materials at Linko?ping University among
others.
Reference:
Padinhare Cholakkal Harikesh, et. al, Organic Electrochemical Neurons and
Synapses with Ion Mediated Spiking. Nature Communications, 2022
DOI: 10.1038/s41467-022-28483-6