Design of a new photochromic oscillator: towards dynamical models of pacemaker neurons

A brand-new photochemical oscillator is designed in this work. It consists of two thermally reversible photochromic compounds. One photochrome is inverse and autocatalytic because the photoproduct emits a fluorescence that enhances its own production. The other photochrome is direct and not fluorescent. The two photochromes have specific spectral features that generate mutual filter effects when dissolved in the same solution and under uniform irradiation. The double photochromic system can originate photochemical oscillations if an essential condition is fulfilled. The autocatalytic photochromic compound must have its photochemical quantum yield and thermal recovery kinetic constant appreciably larger than the other photochrome. The conditions favorable for having photochemical oscillations are quantitatively described. This new photochromic oscillator, working in isothermal conditions, is an alluring model of pacemaker neurons, which can communicate with other artificial neuron models through optical signals. It constitutes a valuable contribution to the development of neuromorphic engineering in wetware. Its characteristics and performances are compared with those of the other photochromic oscillator that has been proposed so far.