Eleanor Hayes highlights some education resources about the nanoscale and nanotechnology.
With the help of many education projects, introducing the nanoscale at school has never been easier – whatever the age of your students. Below are two experiments (for children aged 8+ and for 14- to 16-year-olds); many more resources are listed at the end of the article.
In the following experiment, suitable for ages 8 and above, food colouring is serially diluted, causing the colour and smell to fade gradually. The colour will fade more quickly that the smell, illustrating that even though our eyes cannot detect the chemical responsible for the colour, it is still present, as verified by the smell.
In the same way as we use our eyes to see large things and our nose to smell small things, nanoscientists use special tools to analyse (and manipulate) things at the very small scale: the nanoscale. Atomic force microscopes can feel and move individual atoms, while special surfaces with nanotextures on them can repel water extremely efficiently.
The experiment is taken from the ‘Time for nano’ project, which offers informal education materials about the benefits and risks of nanoscale research, engineering and technology. The website and materials are available in nine languages (Dutch, English, Finnish, French, German, Italian, Polish, Portuguese and Turkish). The project members – science centres across Europe – also offer ‘nanodays’, with demonstrations, experiments, games, meetings and discussions about nanotechnology. For more information, see the Time for Nano websitew1.
When introducing the activity, the following examples may help to illustrate how small the nanoscale is.
Encourage students to consider the things that they cannot see directly, for example the ozone layer, dyes in stained glass windows or the colloidal nature of milk.
Explain that the olfactory bulb of the brain is responsible for interpreting the smells that the nose detects. The olfactory bulb is strongly linked to a part of the brain that is responsible for remembering things, which is why certain smells can make us remember specific things clearly.
The students can calculate that in each tube, the food colouring is ten times more dilute than the previous tube. By the time they reach Tube 9, the original food colouring has been diluted to the level of one part of food colouring to a billion parts of water.
At what point can you no longer see any colour in the tubes?
At what point can you no longer smell anything in the tubes?
How can you explain the difference?
The method you have just used is called a serial dilution. If you wanted, in just one step, to dilute 1 ml of the food dye to the same concentration as in Tube 9, how much water would you need?
Liquid crystals have properties between those of a conventional liquid and those of a solid crystal; for example, a liquid crystal may flow like a liquid, but its molecules may be oriented in a particular direction, as in a crystal. Liquid crystals are sensitive to external factors, such as temperature, and change their molecular arrangement when these factors vary. In response to a change in temperature, some types of liquid crystal (thermotropic ones) change colour as a result of a change in assembly.
In this experiment, students investigate colour changes in a thermotropic liquid crystal and then build their own liquid crystal thermometer. The protocol, which is suitable for students aged 14-18, was developed as part of the ‘Nanoyou’ project. Extensive supporting materials are available (in Danish, English, German, Italian, Portuguese and Slovak) from the project websitew2.
The Nanoyou website is available in 12 languages and offers a range of free materials, including posters, presentations, card games, role plays and a teachers’ training kit. This kit covers the fundamental concepts in nanoscience and nanotechnologies; applications of nanotechnologies; four laboratory experiments and a virtual experiment. Separate kits are available for the 11-13 and 14-18 age groups.
Schools that participate in the project work directly with leading European nanoscience research centres, receiving nanotech-related materials and taking part in workshops. Particular focus is given to ethical, safety and social implications, as well as present and future limits to scientific development. To learn how to get involved, visit the Nanoyou websitew2.
For this experiment, you will need four different mixtures prepared from three liquid crystals:
The instructions for preparing each of these liquid crystal mixtures (‘Student synthesis procedure’) and supporting material for teachers are available to download from the Nanoyou websitew2.
Solids should not be inhaled. Wear gloves and safety glasses; contact with skin, eyes or clothing should be avoided. Wash your hands thoroughly after handling the liquid crystals.
|Liquid crystal mixture||Sensitivity temperature (°C)||Cholesteryl oleyl carbonate||Cholesteryl pelargonate||Cholesteryl benzoate|
Use the room thermometer to determine the temperature in the room you are in.
Could any of your liquid crystal mixtures be used to determine the room temperature? If so, which one?
Why do you get different results when you test the liquid crystal sheets against white paper and black paper?
Did all four liquid crystal sheets display some colour? If not, why not? What could you do to make these sheets display colour?
|White paper||Black paper|
|Sheet 1 (mixture 1)|
|Sheet 2 (mixture 2)|
|Sheet 3 (mixture 3)|
|Sheet 4 (mixture 4)|
|Liquid crystal sheet number 1|
At what temperature do you start to see some colour in sheet 1? Does this correspond to the temperature predicted in Table 1?
Does the order of colours that you have recorded in the table above follow a particular pattern? If so, what pattern and why do you think this might be?
Imagine putting sheet 1 in a water bath of unknown temperature. If the sheet turned orange what temperature would the water be?
|Liquid crystal sheet number 2|
|Liquid crystal sheet number 3|
|Liquid crystal sheet number 4|
Was the colour sequence that you observed for sheets 2-4 the same as for sheet 1? Why/Why not?
When you take sheets 2, 3 and 4 out of the water bath, do they behave like sheet 1? If not, what is the difference? Why?
Which of the four liquid crystal mixtures would you use to see whether you have a raised temperature? Why?
Does your room thermometer show any colour? If not, why not?
If your thermometer does not show any colour, try placing it over a working laptop computer. It will demonstrate what we all know – that they heat up.
Your thermometer will last 3-6 months, after which it can be disposed of as normal waste.
The properties of materials at the macroscale are affected by the structure of the material at the nanoscale. Changes in a material’s molecular structures are often too small to see directly with our eyes, but sometimes we can see changes in the material’s properties. Liquid crystals are an excellent example, in particular the type used in this experiment, since their optical properties (colour) change visibly as the temperature of the liquid crystal is changed. In nanotechnology, scientists take advantage of the peculiar properties of materials at the nanoscale to engineer new materials and devices.
Time for Nano is funded by the European Commission under the 7th Framework Programme.
The liquid crystal experiment published on the Nanoyou website was adapted from the ‘Preparation of cholesteryl ester liquid crystals’ – one of the many experiments listed on the website of the University of Wisconsin-Madison, USAw4 – and from the ‘Exploring materials: liquid crystals’ activity developed by the Nanoscale Informal Science Education networkw5.
The ‘Nanoyou’ (Nano for Youth) project is funded by the European Commission under the 7th Framework Programme (FP7/2007-2013) under grant agreement 233433.
Mallmann M (2008) Nanotechnology in school. Science in School 10: 70-75. www.scienceinschool.org/2008/issue10/nanotechnology