Sensitive Textiles

By Roland Piquepaille

According to a short article by PhysOrg about Intelligent Fabric, a British company, Eleksen, is manufacturing flexible sensors and switches that can be integrated into everyday objects such as cell phones, teddy bears or car seats. "The textile sensors can measure how hard they are pressed and also whether moisture is present." For example, these sensors could be used in hospitals to know if incontinent patients need a bed linen replacement or if other patients have left their beds. As these sensors can be woven in all kinds of textiles, you'll soon be able to create your own clothes and applications. And as they're very robust, it will be even possible to put them in your washing machine to clean them. Read more...

Here is what writes PhysOrg about this new kind of fabric.

The fabric is a combination of conductive fibers and conventional textile fibers. It consists of two external, electrically conductive nylon layers. Between these two layers is a layer of insulating material, into which are woven individual conductive fibers. On the outer layers there is a low measuring voltage supplied by a battery. If the user exerts pressure on the outer layers -- with a finger, for example -- the voltage changes. The sensor detects this change and can thereby precisely determine the amount of pressure exerted and its position. The thin sensor layers are capable of withstanding enormous strain -- not even the weight of a car will damage them. A more sensitive application might be a doll that begins to cry if it's pressed too hard and laughs when it is tickled.

Here is an example of how it is possible to integrate flexible sensors into everyday objects such as cell phones (Credit: Siemens AG).

The above illustration has been extracted from the Fall 2004 issue of Pictures of the Future, published by Siemens AG.

Even if it is a promotion for the Siemens group, it's quite interesting. Here is a link to the full issue (PDF format, 47 pages in the PDF file, 94 pages if you want to print it, 5.13 MB). The story about these sensors appears on page 33 of the PDF file (page 64 of the printed version).

Here are the explanations by Siemens on how the system works.

A low measuring-circuit voltage is applied to the layers by the device (for example, an MP3 player) or by a battery. If the sensor is touched, the pressure establishes a connection between the conductive layers, making it possible to measure where the sensor is being touched. The strength with which the sensor is pressed can also be determined. As the pressure increases, more conductive fibers touch each other. The result is a stronger electrical current.

Because this new kind of sensors can be used for many applications, what will be coming next? Maybe flexible keypads for mobile phones or automotive controls integrated into car seats. But as Eleksen is working with more than 80 different companies, the applications from these sensors might be something we're not even thinking about today.

Sources: PhysOrg, November 5, 2004; and various websites