Excitability Modulation of Oscillating Media in 3D-Printed Structures

Abstract

Excitation and oscillation are central to living systems. For excitable systems, which can be brought into oscillation by an external stimulus, the excitation threshold is a crucial parameter. This is evident for neurons, which only generate an action potential when exposed to a sufficiently high concentration of excitatory neurotransmitters, which may only be achieved when multiple presynaptic axons deliver their action potential simultaneously to the synaptic cleft. Dynamic systems composed of relatively simple chemicals are of interest because they can serve as a model for physiological processes or can be exploited to implement chemical computing. With these applications in mind, we have studied the properties of the oscillatory Belousov-Zhabotinsky (BZ) reaction in 3D-printed reaction vessels with open channels of different dimensions. It is demonstrated that the channel geometry can be used to modulate the excitability of the BZ medium, switching a continuously oscillating medium to an excitable medium. Because large networks of channel-connected reaction wells of different depth can easily be fabricated by 3D printing, local excitability modulation could be built into the structure of the reaction vessel itself, opening the way to more extensive experimentation with networks of chemical oscillators.

Fabricating millifluidic reaction-diffusion devices: Droplet-in-oil networks structured by laser cutting

“…The diffusion of iodine through the main channel slows down after ~2 hours. After ~5 hours starch colouring is not triggered in chambers [13][14][15][16][17][18][19][20]; the maximum diffusion distance of iodine is 60 mm. Fig.…”

“…We have previously described BZ wave propagation in 3D-printed reaction vessels where the channels and the wells contained BZ medium in direct contact with the air [5,13]. The reaction-diffusion medium was physically structured but a two-phase system was not implemented.…”

Belousov–Zhabotinsky reaction in liquid marbles

“…To provide insights into these processes and the use of BZ media for the applications above, previous studies utilised the BZ reaction in spatially confining media such as thin hydrogel films [41], small droplets in microfluidic devices [32,[42][43][44][45][46][47][48][49][50][51][52], vesicles [53][54][55][56][57], emulsions [58], BZ-AOT emulsions [9-11, 17, 59-64], cation exchange resins [65][66][67][68][69][70][71] and 3D printed structures [42,72,73].…”

“…To provide insights into these processes and the use of the BZ media for the applications above, studies have focused either on thin films of media or on confining the BZ reaction in small droplets in microfluidic devices [20,[27][28][29][30][31][32][33][34][35][36][37], vesicles [38][39][40][41][42], emulsions [43], BZ-AOT emulsions [5,[44][45][46][47][48][49][50][51][52], cation exchange resins [53][54][55][56][57][58][59] and 3D printed structures [27,60,61].…”