# Is elastic wiring feasable?

Since wireless does not seem to be the ultra-high-broadband solution of the future (according to recent 5G cellular network results), wires seem the only way to go for a data-intensive future.

The difficulty with wires is their management, and they must either be rolled up somewhere (if the cable is too long) taking up space or custom-length, which does not allow moving the cable aside to reach equipment behind it.

The science-fiction solution would appear to be wiring which can adjust in length.

Is it feasible for humankind to have elastic, conductive wires with our current understanding of physics?

The price or practicality of the wires is of no concern.

• Fundamental flaw with question. Conductive wires aren't used for ultra-high-broadband data-intensive communications. Fibre Optics are used and they are extremely fragile. Wireless supports very high bandwidth and speed. Modern game controllers on console all use variations of bluetooth and short range wifi. Second flaw is a stretching cable would mean a longer distance for data to travel, resulting in more degradation of the signal, leading to random difficult to solve errors that will be the result of a broken cable somewhere in a wall somewhere. A nightmare – Trevor Sep 26 '19 at 13:19
• @Trevor Stupid me, of course it is. Nevertheless I find it an interesting question. – A Lambent Eye Sep 26 '19 at 13:41
• "5G" is marketing speak for a family of cellular communications technologies. They are not intended as a replacement for local area network communications technologies. High-efficiency wireless local area wireless data communications technologies such as the WiGig family (including 802.11ay) and 802.11ax are intended to enable devices to communicate at multi-gigabit per second. In short, comparing cellular technologies such as "5G" with wired LANs is a category error. – AlexP Sep 26 '19 at 13:58
• @AlexP Thank you for pointing that out, I was unaware of the fact. – A Lambent Eye Sep 26 '19 at 14:00
• For fun, you can looking into AWS's snow globes or their Snowmobile. Basically, transferring huge amounts of data over cables onto physical storage and shipping it is faster than sending it over the internet. Just imagine being able to transfer 1 Terrabyte per second. – Shadowzee Sep 27 '19 at 0:35

Coiled wire such as that used on old-fashioned telephone sets (as below) (I cannot for the life of me find a Wikipedia article mentioning this kind of cord) allow a limited amount of flexibility, but can easily be twisted incorrectly and over-stretched, damaging the wire.

I do not know why this technology is no longer used and any pointers towards resources referring to it would be greatly appreciated.
Old fashioned green telephone by şaban uluca on Flickr

Creating a more exotic conductive chain and covering it in a tight, elastic fabric could achieve the desired effect.

Potential drawbacks could be:

• Major friction on the internal chain links during usage
• Limited flexibility
• Cables containing multiple wires would be very difficult to achieve
• Copper, aluminium and gold could be too soft, allowing the chain to tear if overstretched: alloys or other less conductive metals would have to be used
• Incredibly arduous manufacturing of individual chain links
• Possible loss of contact between chain links
• And much, much more
• What you're after is a loading coil , that's part of it, I've just found a reference for: Curly Spring Coiled Spiral Telephone Handset Cable Wire (commercial website - beware) Overly elaborate name. – Tantalus' touch. Sep 26 '19 at 14:33
• @Measureofdespare. This is the doing of search-engine optimisation. Cursed be thee, Google! – A Lambent Eye Sep 26 '19 at 15:15
• Can't beat the good old fellytone! – Kevin Kostlan Sep 27 '19 at 0:18
• Why it is no longer used: Because it's "pull" is far too strong and the bouncyness far too annoying for most use-cases [IMHO] – Hobbamok Sep 27 '19 at 11:02
• Just want to point out it is still used quite widely. For example, my headphones (pretty modern and on the higher quality end) use a coiled wire. I wonder if there is something about analogue vs digital though. – Alice Sep 27 '19 at 12:23

The difficulty with wires is their management, and they must either be rolled up somewhere (if the cable is too long) taking up space

Your assumption seems wrong to me. Rolling cables is every engineer's favorite way to save space.

If the distance between two points you need to link is going to vary, the proper way to do things is to use a reel. These exist in many sizes, for practically every application you can think of.

And I mean every application. See some guys standing on a reel for submarine fiber optics cables:

Using elastic cables would vary the conducivity of the wiring (see mcRobusta's answer) and would add other hazards, such as the cable getting stretch-stuck on unwanted places due to someone or something moving it around. If instead you use proper reeling on strategic places, you keep things neat, easier to service and easier to pack up and move if need be.

• It should be noted: For high current loads, one should be VERY careful to avoid actually running power while the cable is mostly wound. hsa.ie/eng/Safety_Alerts/2014/Electric_Cable_Reel_Alert Cables are generally rated with expectation that they are not thermally blanketed, and that includes insulation by layers of the same cable wound around itself -- the heat dissipation may not be sufficient. See electronics.stackexchange.com/questions/192923/… (Also, coiling an unpaired wire can cause a strong magnetic field.) – Jacob C. Sep 26 '19 at 22:28
• @JacobC. you can't make an omelet without starting some fires :D – The Square-Cube Law Sep 27 '19 at 12:12

## No. The resistance would be hilarious.

The resistance of a wire is given (simply) by this equation:

$$R = \frac{\rho L}{CSA}$$

where, $$\rho$$ is a material-dependent constant, $$L$$ is the length of the wire and $$CSA$$ is the cross-sectional area of the wire. As you stretch a wire (or indeed any material), its cross sectional area decreases whilst its length increases. For an example, let's take copper.

This copper wire is $$1m$$ in length and has a radius of $$1mm$$, giving it a cross-sectional area of $$\pi * 10^{-6}m^2$$. Given the $$\rho$$ of copper is $$1.68*10^{-8}\Omega/m$$, the resistance of this wire is:

$$R = \frac{1.68*10^{-8}}{\pi*10^{-6}} = 5.35*10^{-3}\Omega$$

Now let's stretch it out to $$2m$$. We can use the Elastic Stretch Equation (found here) to calculate the percentage change in wire length, and rearrange to find the new diameter and thus CSA (note I've changed imperial to metric, hence the ugly constant):

$$\%\,Change = \frac{293.25M}{D^2}$$

$$M = \delta*v = 28.1g = 0.0281kg$$

$$100 = \frac{8.24}{D^2}$$

$$D^2 = 0.0824mm^2$$

$$D = 0.287mm$$

$$New\,CSA = 6.47*10^{-8}$$

$$New\,Resistance = \frac{2 * 1.68*10^{-8}}{6.47*10^{-8}} = 5.19 * 10^{-1}\Omega$$

As shown, doubling the length of copper wire gives it 9,700% of its original electrical resistance (or its resistance is 97 times bigger than before). Aside from heat generation alone, not many electrical signals are going to get through this.

With all that being said, the field is a work in progress. Things like conductive fabric are using smart geometry, topology, wire shorting etc. to get better, and the field is showing more promise every day.

Hope it helps!

• Wow! A fascinating demonstration of formula wizardry! Would 97'000% not be a factor of 970, instead of 'just' 97 (as you stated)? – A Lambent Eye Sep 26 '19 at 14:30
• You are totally correct- my math was fine until the end. Will append in an edit (and thank you very much) – mcRobusta Sep 26 '19 at 15:11
• @mcRobusta: I am really sorry, but I truly don't follow. Volume is length times cross section. If you don't add or subtract copper then volume must remain constant. If length goes up by a factor of 2, then cross section must go down by the same factor of 2, to maintain constant volme. This is pure geometry. Resistivity doesn't change. (And the elastic stretch equation is a red herring; it serves to compute the relationship between mechanical tension and relative stretch, which is utterly irrelevant and not applicable. I'm not completely certain whether mentioning it is a subtle joke, or what?) – AlexP Sep 26 '19 at 17:58
• Its worth noting that copper wiring is still widely used in short-range applications in Ethernet cables – 0something0 Sep 26 '19 at 18:31
• @Mark: Yes, it does, bit the factor of change is four not one thousand. – AlexP Sep 27 '19 at 6:33

I would have thought, given the availability of conductive lycra fabric (I've just googled it and had a fair few hits!), the answer to this is yes.

This fabric looks and feels like ordinary Lycra but is highly conductive. It can be cut into narrow strips to form conducting ‘wires’ or can be used as a soft compliant substitute for metal and foil in switches and sensors

At the moment this fabric is predominantly used for wearable electronics.

Possibly a better solution would be using electric nano-materials https://aip.scitation.org/doi/10.1063/1.5083942. This would allow wiring that acts pretty much like a rubber band.

In the paper above it's using copper wires in a coil inside a substrate, but it also mentions using nanotubes or silver nanowires, and also structural folding such as origami to allow stretching.

• Welcome to the Worldbuilding Stack Exchange! Your answer is currently a little short, please embellish and elaborate on it a little, such as describing what makes the Lycra conductive and what other properties it has and perhaps adding images. – A Lambent Eye Sep 26 '19 at 13:44
• That's better, can you add a little more from the second link? – Trevor Sep 26 '19 at 14:02
• Thank you to Trevor and A Lambent Eye for the hand holding :) – Riddles Sep 26 '19 at 14:21
• You're very welcome, having more valuable people like yourself on our site keeps it alive and thriving! – A Lambent Eye Sep 26 '19 at 14:31

The answer to the question of advancing bandwidth to our portable devices, where a dedicated pre-selected length of wire would be undesirable, lies not in finding a better way to make a hardline wire to it, but making better use of wireless design.

High bandwidth optical communications, such as what we use in fibre optics, can work surprisingly well as a wireless system. However the transmitters and receivers require direct line of sight, and may be interfered with due to weather conditions. [or someone/something stepping into the beam...] The other drawback of running open optical systems is that they can quickly reach a saturation point where sending-receiving pairs that are spaced too close together will risk cross talk as the receiver from Pair A begins to pick up parts of the signal from Pair B's transmitter.

Along with removing the requirement of line of sight, routing optical signals through dedicated fibres means we can pack far more Sending-Receiving pairs into the same space.

It is really this cross talk risk that is the heart of our bandwidth problems, whether dealing with Optical, Cellular Signals, or home WiFi, we will quickly saturate an area with competing signals if we use devices that blast data over a wide area without concern for where the other end is going to be.

So, how do we resolve this?

We begin limiting the wireless signals to more confined and better defined regions.

This concept is seen all the way back with the original cellular networks [and is why they're called cellular...]. Rather than broadcasting one signal that can be seen everywhere, you split "everywhere" into smaller regions that are covered by weaker signals [such that signals don't overlap any more than needed], and you can then squeeze more data through the whole system.

As such, we apply the same solution by adjusting the scale again. We use smaller cells that will cover fewer users, freeing up more of the max transmission bandwidth for each user.

Have a Network Signal that covers an entire neighbourhood that is becoming overloaded?

• Run hardline to each house, and give each house a smaller wireless network that doesn't spread much beyond each person's yard.

Is the 'whole yard' system getting saturated?

• Run hardline to each room in the house, and give each room an even smaller wireless signal network so that devices in different parts of the home aren't trying to 'talk over' each other.

Need more bandwidth in the room?

• Again go smaller and more focused. Rather than broadcasting a blanket signal across the whole room, use a different wireless style that focuses better and sends tighter beams aimed at individual devices.

Need to go even smaller?

• Cover the ceiling with an array of transceivers that can beam data directly at the device with laser like precision... [Just remember to design it in a way that avoids blinding people... Using actual lasers that can be misdirected off mirrors or something could be problematic, but there are totally ways around that sort of thing.]

Yes, and it's already commercially available. This stuff can apparently change length up to 40% with NO CHANGE in resistance.

https://mnwire.com/istretch/

• Welcome to the Worldbuilding Stack Exchange! At the moment your answer is a little short, could please describe this technology in further detail, perhaps adding a quote or an image from your source? This would improve the quality of the answer and make it more likely to receive votes. – A Lambent Eye Sep 27 '19 at 7:38
• According to the pictures on the bottom of the page, it is only slightly updated coiled wire from currently highest-voted answer and thus it has all the inductive flaws of your regular coiled wire. – Mołot Sep 27 '19 at 13:36