# Strechable object that can transfer current

Does some material/metal exist that can be stretched and still transfer current?

For example: Say I have a rectangular item made of some metal or material(unknown to me at the time). On both ends, I have two small sensors attached. These sensors do nothing but want to establish communication between each other. For the purpose of this question, let's refer to them as sensor A and sensor B. Sensor A sends a message to Sensor B. Since the metal is not very stretched, it manages to transfer the message in electrical current to Sensor B in an elapsed time of .1 second.

Now, imagine that we stretch the metal a bit more, where its width is lowered and its length is increased. Since the message now has to travel further, I would expect the delivery to be greater than .1 second.

Note: Numbers used are just an example.

• What sort of material or metal can I use to pass current, that when stretched, would alter the total distance a current would have to travel?

• Ideally, the two sensors will at the minimum be separated by 3-4 inches, and the metal/material would only stretch up to 1 inch.
• Is the purpose of the system to measure the message propagation time? – Donald Gibson Jan 19 '17 at 23:36
• the purpose was to measure distance between two sensors, where the material they communicate on can be dynamically expanded. i was going to use message propagation time as a means to calculate distance – angryip Jan 20 '17 at 0:02
• What kind of scale are you looking at? Strain gauges do this already to measure deformations in materials. – JMac Jan 20 '17 at 0:11
• scale of change is centimeters. i want to desing a medium that can allow teo of my arduino sensors to communicate – angryip Jan 20 '17 at 0:16
• The usual method for measuring distances at that scale when you can stretch something between the points to be measured is the "string potentiometer". Simple, reliable and easy to interface. – Dave Tweed Jan 20 '17 at 13:06

First of all, with your 4 inch distance, the propagation time wouldn't be 0.1 seconds. It would be 0.000 000 000 339 seconds. Measuring such short time differences is a significant challenge and there are no obvious off-the-shelf solutions capable of it.

But more than that, the propagation time doesn't depend only on the distance. The shape and surroundings of the conductor also affects it, due to transmission line effects. Thus even if you had the propagation time, it would need a more accurate modelling of the situation to arrive at a distance reading.

You may want to ask another question about what kind of distance sensors would be applicable to your problem, but you'll also have to give more details about the actual goal that you want to achieve.

Given the theoretical dimensions stated in the question, there would be no measurable difference in the transmission speed of the message.

Possible materials include various conductive rubber compounds, where a conductive filler, such as copper, aluminum or nickel particles are mixed with a flexible carrier such as silicone rubber, latex or other elastomers to suit requirements.

Google "electrically conductive rubber" for some commercial products.

• is there a better way one could measure the distance between two sensors, inferring that the communication medium can dynamically expand? i.e if i used the electirc rubber – angryip Jan 20 '17 at 0:04
• @angryip This is what strain gauges do assuming I'm interpreting what you want correctly. Look them up and see if it's appropriate for your application. – JMac Jan 20 '17 at 13:26
• If the measurement is macro - i.e. measuring 0 to 3 cm, a set of digital calipers with USB readout would measure within 0.0005" over the full range. As others have mentioned, micro distances can be reliably measured with strain gauges. If something less sophisticated is needed, a standard dial gauge would do the job. – Donald Gibson Jan 20 '17 at 20:07