Answer by Christoph Marschall, Technology Strategy Manager, on Quora,

It's not just the screen which is hard to produce, it's the whole range of problems that come with it, each of them very unique to the shape of the device.

Let me try to summarize some of them:

A conventional LCD glass panel consists of 2 layers of glass, with the Liquid crystal array and the wiring between them. That bus-wiring is heading to one edge of the screen, is then bundled together outside of the actual visible screen area and leads into a display controller which either sits on the glass or on the ribbon cable connected to the panel. In any case, those wires need to come together from a rather spacious arrangement to a small one.

On a rectangular screen this is happening either on top or bottom, via a "lip" of the panel (one of the glass sheets is slightly longer than the other, so all the lines can come together and a cable can be connected there.)

On a round screen those wires cannot simply come out of the bottom, they would have to come out everywhere from the lower half of the screen (outside of the viewable area), then wired along the screen down to the bottom, and on the bottom you need a "lip" again to connect a flex-cable.

So, the bezel of the panel would be rather big, and the device cannot be made fully round due to the required lip on the bottom.

2. Screen yield (the successful production rate)

I can't name figures here, but the production of non-rectangular screens is suffering from a lower yield than rectangular screen, because you cannot do a smooth linear cut of the glass but have to cut along a path. Lower yield means you have to produce more than one screen to get a working screen panel, a multiplication of your (already high) production costs.

Plastic OLED (like a glass panel above, but based on plastic instead) allows to create custom shaped screens much easier because the panel doesn't suffer from the mechanical stability when cut differently, and the wiring of the individual pixels can be done in a smaller bezel.

However, the first POLED-based product has only been commercialized this year, the LG G-Flex. So the technology is still really expensive.

However, building a round device with a round POLED screen is more feasible than using glass.

When producing a non-rectangular screen, you are targeting a rather premium product, because it's supposed to be a novelty. So you don't want pixelated edges, but very smooth, round screen-content. That means you need a resolution at least above 300ppi (pixel-per-inch), which is driving the price further up, for a market (wearable) that is considerably small as of today (between 1m~22m units globally in 2013 according to various sources, the exact number is not known as most of the current players in that industry are privately owned and thus don't have to report sales figures).

Similar to LCD screen but kinda worse. A touch panel consists of very fine vertical and horizontal wires going across the screen. A touch on the screen is detected because a horizontal and a vertical line are connecting (through your finger). So you have vertical lines coming out of the bottom of the panel, AND horizontal lines coming out of the sides of the panel. They all have to be wired out into a touch controller circuit.

Image source: LG G2 launch-event 2013

On a rectangular screen, they are running down the sides into one direction. On a circular screen, they would have to run circular along the side, on top of the display wires explained above in #1 (LCD-Screen), adding further to the overall size of the Bezel around the screen, and also adding potential interference to the signal.

When designing such a round device with a narrow, round bezel, all your components should fit onto a round PCB as well. With mostly square components this is very hard to achieve. And since you'd like to drive a rather high resolution, want wireless connectivity (I guess?) and some kind of connector as well, you cannot be that picky. Situation got better in 2013/2014 though, with more universal components and more integrated solutions (SoC) available.

There was no existing software that could be used for a round UI until now. You had to develop it completely on your own, including the UX that goes along with it. Another significant cost-factor to consider when designing such a device, because given the price you reached already for the hardware, you need a software which is very functional and also compatible with a wide range of devices and applications. Also here the situation got better though, with Android Wear offering a versatile framework to easily develop a round device without having to bother much about UX and interoperability, it is limiting compatibility to Android though and prevents you from differentiating drastically from the rest of the market.

This list is not complete, there are several more items to consider, but I think you get the idea.

Overall, as always its a matter of money. There are lots of issues. Those issues can be overcome, but it's very VERY pricey as you mostly need custom solutions for your single product. But at the same time its not clear how many of those devices you could actually sell, and if they won't be produced in big volume and cost a lot in the end.

NPD states that the average buyer of a wearable is not willing to pay more than 300$ for a product [1]. So it looks like you don't know how many devices you could actually sell AND that you would have to price them below 300$ to get a piece of the current (max. 22m units) market. A market which is moreover currently owned by products in the 100$ range. Not really a good precondition to risk everything...

But as said, the situation is getting better. A lot changed in the last years and 2014 might be the year of he first round touch screens in round devices.

This question originally appeared on Quora: Why is making a round touch screen so difficult? More questions: