Phase shifting in a chemical oscillator to encode analogue information

Abstract

We demonstrate that analogue information can be encoded by the use of a chemical threshold system such as the minimal bromate (MB) reaction. The threshold in the chemical system is represented by a subcritical Hopf bifurcation, where the flow rate is the bifurcation parameter. A periodic variation causes the flow rates to cross the threshold periodically at the subcritical Hopf bifurcation. As a consequence, the system responds with oscillations (spikes) of high amplitude. When the average flow rate is shifted by a quantity called the bias the threshold is crossed at different phases of the periodic flow-rate signal and the oscillations appear with different phase shifts. The different phase shifts between the periodic flow-rate signal and the response represent the encoded information contained in the bias. In order to optimize the effect of phase shifting we investigated four different types of periodic flow-rate modulations. A modified sawtooth function turned out to be the optimal periodic signal for the MB reaction. For computer simulations we use the Noyes, Field and Thomson model (NFT) which shows very good agreement with our experiments.