Manipulating reaction-diffusion waves with light

Niklas Manz

A reaction-diffusion wave’s propagation behavior can be influenced by varying the illumination intensity of visible light (e.g., placing a printed overhead transparency between the light source and the BZ medium or illuminating the system with a projector).

Schebesch and Engel (Schebesch and Engel, Wave propagation in heterogeneous excitable media Phys. Rev. E 57, 3905-3910, 1998) calculated numerically the propagation behavior of light-sensitive excitation waves in a pure checkerboard-like illuminated system as shown in the next figure. The goal of this projects is i) experimentally prove the predicted 1D and 2D behavior and ii) expand to different illumination patterns.

Checker board

Numerical result of a propagating RD wave (from Schebesch and Engel, 1998)

Spencer Kirn started this project as his Senior IS in 2016 and built the setup and got some preliminary results. Daniel Blaikie investigated the use of various light-sensitive catalysts during the 2018 NSF-REU summer research experience and implemented the use of a projector for better illumination control during his Senior IS in 2018-2019.

We are working on a 1D-system with alternating excitability to experimentally verify Schebesch and Engel's 1D-result that, under specific conditions, the wave propagates faster than in a medium with homogeneous mean excitability. It is also expected that propagating waves in a 2D-system survive while their 1D counterparts experience propagation failure at the same system's "wavelength". Other steps planned are varying i) the initial propagation angle, ii) the wavelength-to-inhomogeneity ratio, iii) the light intensity difference ΔI (excitability difference), and iv) the illumination pattern.

sin-sin mask chess scale mask gray level mask

Examples of possible illumination patterns. Varying light intensity pattern while keeping the average intensity I constant (left and center). Different general illumination pattern and propagation directions (right).

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