Chemical-to-electrical-to-chemical signal transmission. A conventional neuron (upper panel) senses chemical signals (orange circles), which trigger an electrical pulse of membrane depolarization (action potential) along the axon, causing chemical release at the axon terminals (blue circles). This process can be mimicked (lower panel) by a chemical biosensor (for glutamate or acetylcholine) connected to an axon-mimicking organic electronic ion pump that transmits electrons/ions and generates chemicals — forming an organic electronic biomimetic neuron. (credit: Daniel T. Simon et al./Biosensors and Bioelectronics)