Organic transistors lead the way towards neuro-inspired computers.

Researchers at the CNRS and CEA have developed a transistor that mimics the functionalities of a synapse. This organic transistor known as NOMFET (Nanoparticle Organic Memory Field-Effect Transistor) is capable of responding in a similar manner to the nervous system. The result comes from the pursuit of new information processing strategies. This approach has attempted to imitate the way biological systems, such as neural networks, operate.

In the nervous system, a synapse is the junction between two neurones, enabling the transmission of electric messages from one neuron to another and the adaptation of the message as a function of the nature of the incoming signal (plasticity). For example, if the synapse receives very closely packed pulses of incoming signals, it will transmit a more intense action potential. Conversely, if the pulses are spaced farther apart, the action potential will be weaker. It is this plasticity of the transmission of an action potential that has been successfully mimicked with the organic transistor.

Normal transistors form the basic building block of most electric circuits.They can function as amplifiers, modulators and encoders but are widely used as a switch for an on/off signal. The NOMFET transistor also has an innovative memory effect which has allowed the imitation of a synapse during action potential transmission.

This advancement was achieved by combining the transistor with gold encapsulated nanoparticles, fixed in the channel of the transistor and coated with pentacene. The resulting performance is comparable to the seven CMOS transistors (at least) previously needed to mimic this plasticity. The devices produced have been optimized to nanometric sizes in order to be able to integrate them into neuro-inspired computers. These can resolve much more complex problems than present silicon computers, such as visual recognition.