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1.9 Physical Contradiction Examples

Aggiornamento: 8 nov 2021

One clear example could be:

Fruit storagewe want air and we don’t want air

When storing fruit, we want it to be fresh for as long as possible; carbon dioxide keeps it fresh but oxygen is harmful. Solutions for keeping fruit fresh include isolating it from oxygen and/or dousing it in an atmosphere of carbon dioxide. Air contains both oxygen and carbon dioxide so we want air and we don’t want air. We want to separate – we want the carbon dioxide near the fruit and the oxygen away from the fruit. Simply by stating the problem in these exact terms helps engineers come up with solutions. Suggested solution Principles for Separate in Space see what each principle suggests then seek further knowledge and resources to work out how to follow the suggested solution. All these suggestions point to some kind of gas permeable film – some way of isolating the fruit from oxygen but not carbon dioxide – a search on the patent database reveals the existence of films through which oxygen can escape but carbon dioxide is retained. Many food substances are packaged with carbon dioxide or another gas such as nitrogen used with crumpets.

This example has been in TRIZ literature for over 10 years. There are now patents applied for as late as 2006 – describing methods for optimal storing and transporting fruit, particularly bananas, and also to provide an appropriate atmosphere for ripening of the fruit. The fruit is placed within a suitably designed flexible bag, which allows the fruit to be open to the atmosphere, but is protected by a flexible cover, which is at least partially gas - permeable and separates the oxygen and carbon dioxide.

1 Segmentation – segment the air

2 Taking Out – take out the oxygen

3 Local Quality – have a layer near the fruit of just carbon dioxide

4 Asymmetry – encourage the air to be rich in carbon dioxide near the fruit and rich in oxygen away from it

7 Nested Doll – nest the gases

14 Spheroidality/Curvature – bubbles of carbon dioxide near the fruit?

17 Another Dimension – multi layers?

24 Intermediary – can we use an intermediary carrier of oxygen to remove it?

26 Copying – can we have some imitation fruit which protects it?

30 Flexible Membranes and Thin Films – isolate the fruit from the oxygen with a thin film

40 Composite Materials – find a material which is rich in carbon dioxide near the fruit

Finding Physical Contradictions

There is much description in the TRIZ literature about the challenge of locating physical contradictions. Ifind that the simplest approach is to begin by defining the Ideal Outcome to help map everything we want – all benefitsno matter how contradictory. Describing all the benefits we want within the ideal usually uncovers physical contradictions, as there are usually opposite benefits. To define how to get benefits we move into functions or features.

We may also begin our definition of a physical contradiction with a description of opposite features or functions. We may think we want something which is both small and big, or fast and slow, or sharp and blunt. Defining a physical contradiction can be by defining opposite benefits or features or functions. Taking our problem description from features and functions back to benefits is generally useful as it gives us greater clarity of what we want and why. To check if it is a benefit – not a feature or function – ask if it contains a solution. Benefits do not describe how they are delivered, but simply what we want. Therefore when first seeking to define a physical contradiction it doesn’t matter if we begin with benets, features or functions. For example we could describe physical contradictions in a toothbrush by opposite benefits, features or functions. Our ideal toothbrush has the opposite benefits of very effectively cleaning teeth but doesn’t clean (hurt) gums. We could describe this as saying we want opposite features of a soft toothbrush and a hard toothbrush or that we want the opposite functions of removing material (removing plaque from teeth) and not removing material (from gums). All three of these give us the route into physical contradictions which can be solved with the Separation Principles and the 40 Principles.

This simple route to defining physical contradictions which can begin with an analysis of the problem, a definition of the ideal or a description of opposite features or functions is described in the physical contradiction map.


TRIZ for Engineers: Enabling Inventive Problem Solving, First Edition. Karen Gadd.

© 2011 John Wiley & Sons, Ltd. Published 2011 by John Wiley & Sons, Ltd. ISBN: 978-0-470-74188-7

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