Belousov-Zhabotinsky reaction

The Belousov-Zhabotinsky reaction is a so called oscillating diffusing reaction. Summarized there are three processes: A, B and C. In process A bromate turns into bromide, in process B bromide turns back into bromate and in process C the products from the reaction will react with each other. The critical concentration of bromide causes the oscillating pattern as it fluctuates from process A to process B. This reaction is made visible by using the ferroin indicator, which turns red when it is in its reduced form in process A and turns blue when it is oxidised in process B as shown in the left picture.

Processes

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We use 5 solutions to create the reaction:

Solution A: 2 ml sulphuric acid and 5g sodium bromate (NaBr03) in 67 ml water                   Solution B: 1g sodium bromide (NaBr) in 10 ml water                                                             Solution C: 1g malonic acid in 10 ml water                                                                             Solution D: 1 ml ferroin (25 mM phenanthroline ferrous sulphate)                                         Solution E: 1g Triton X-100 (a kind of detergent) in 1 litre of water

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We put 6 ml of solution A into a petri dish, add 1-2 ml of solution B and 1 ml of solution C. The solution turns a brownish colour. After a minute or so the brown colour will disappear. Once this has happened, we add 1 ml of solution D and a drop of solution E and the liquid tIMG_7880urns red. We swirl the petri dish gently to mix the solutions. It will turn blue and then quickly reverts to red again. Gradually, blue spots will appear randomly and the reaction will start. Below there is a video of our first experiment. In real time the reaction lasts about 45 minutes as it evolves chaotically, in the video it has been speed up 8 times.

Week 3: Hands-on in the laboratory

A lot of progress has been made this week. During the first meeting we put together our findings about pattern properties. We concluded that patterns can have a big influence when it comes to pressure and shock resistance and this is also something we can investigate and apply easily. Our global idea is to let the Belousov-Zhabotinsky reaction create a pattern that follows a pressure distribution. We can apply this in a product like a bicycle saddle, a chair, barstool, a shoe sole or a pillow.

pressure1small SIT-CATscience1A basic visualization of a pressure distribution in 2D and 3D

Tuesday Zjenja informed us that the chemicals would be delivered shortly. As preparation we built a holder for our petri dishes that allows us to make clear pictures. This is important because unwanted shadows and disturbances interact with the grayscale intensity and this gives an unwanted pattern in monolith. The holder also gives us room to interact with the reactions.

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It took a while before the chemicals for the Belousov-Zhabotinsky reaction were delivered but this Thursday we received the essentials and we were able to start our work in the lab. We walked through the process with Zjenja and executed the reaction for the first time. We are still missing some materials so next week we will be doing more accurate experiments. This week we had time to figure out the best way of getting a homogeneous pattern. We posted our findings in the research folder.

Next week we will start interacting with the reaction. How can we transfer the information about the pressure distribution to the reaction? Some ideas we want to try out:

  • Letting the pattern start at a certain position
  • Using heat
  • Using light
  • Touching the reaction
  • Changing the concentrations
  • Adding indicator
  • Starting the reaction on a surface with relief

Besides executing the reaction we will also be focussing on printing new models. We need to get a better grip on monolith and the connex3 printer to get a model in which the pattern is as clear in 3D as it is in 2D. One of our ambitions is to print with multiple materials at the end of next week.

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