So, it’s surprising that the launch of a new minimalist wristwatch has caused such a buzz, especially as its only function is telling the time – it doesn’t have integrated GPS, Bluetooth wireless technology, in-built pedometer or even an alarm. It’s just a clock. But the reason for all the excitement 
is due to the technologies within that have earned it the title of the ‘thinnest watch in the world’.

Created by the Chicago-based company Central 
Standard Time (CST), the CST-01 features an E Ink display 
housed in a single piece of stainless steel. It is 0.8 milli-metres thick and weighs in at just 12 grams. “The CST-01 
is the most minimal expression of a timepiece,” says Jerry O’Leary, co-founder of CST. “It’s ‘time’ embedded in a band.”

O’Leary, an industrial designer and mechanical engineer, and fellow co-founder of CST, Dave Vondle, an interaction designer and electrical engineer, have spent the past year working on their timepiece outside of their day jobs at the design consultancy IDEO.

The inspiration for the watch actually came from a previous IDEO project where Vondle was experimenting with 
E Ink segmented displays, which are ultra-thin, flexible, rugged and only require minimum power to operate. He had been working on a bespoke font for use on such displays.

“E Ink segmented displays differ from the types of pixel-based E Ink displays seen on something like the Amazon Kindle,” explains Vondle. “Think of old LCD watches with the traditional ‘figure 8’ seven-segment design for the numbers. The display we use is driven like that, but we designed much nicer numbers than the traditional seven-segment approach.”

It was when Vondle discovered a new micro controller with built-in E Ink drivers and a real-time clock that he realised that their idea for an E Ink display wristwatch could become a reality. “The all-in-one ultra-thin micro controller System on a Chip (SoC) from Seiko Epson was the missing piece and we started working on our designs soon after it was available.”

The initial aim was to create a word clock that would spell out the time in words before converting to the numeric format when placed on the wrist. But increasing the complexities of the design meant multiple driver chips would be needed alongside the SoC. “We decided to look at the challenge again, but this time taking the capabilities of the Epson SoC as a constraint,” comments Vondle.

Now, with only 64 segments available, they decided to focus on a purely numeric time display. This meant tweaking the original font design, a challenge that Vondle relished, to the point where they arrived at 
a final segment map that used 63 of the 64 available segments.

As Vondle is an interaction designer, the way the 
user would interact with the watch was very important. 
“The most interesting interaction component is actually in the orientation of the numbers. We initially thought through ways we could rotate them like a traditional watch, but we found that when you make the numbers as big as we have, the traditional gesture of holding your hand to your face is unnecessary. 
In most circumstances, you can just glance at your wrist and the display is orientated in a better way for viewing,” explains Vondle.

As well as the E Ink display, O’Leary and Vondle were also concentrating on the design of the watch strap itself. They toyed with various ideas, including the traditional strap with buckle, but soon dismissed this as it wouldn’t allow them to achieve the goal of creating the thinnest watch in the world. So, they eventually landed on the idea of placing the E Ink display on 
a stainless-steel band that could be worn like a cuff 
or bracelet.

They also needed extremely thin batteries and after 
a few failed tests and other options, they came across the Thinergy micro-energy cells. These paper-thin batteries from Colorado-based Infinite Power Solutions are flexible and rechargeable. Having carried out extensive tests on them, Vondle and O’Leary discovered that the Thinergy cells lasted through 4000 bends at a radius of 22.5 mm and still held 85 per cent of the capacity that the cell had on the first charge.

Happy with this, they designed an external docking station where the watch could be placed in order to charge the cells. A 10-minute charge would last a month, with the cells themselves lasting up to 15 years. This docking station would also be used to set the time on the watch, which meant that no buttons or knobs were needed on the watch, further contributing to its minimalist aesthetic.

With all the components in place, the next task was layering them together. “As well as the E Ink display, Micro controller SoC and micro-energy cell, there are also a handful of tiny electronic components that support the SoC, including resistors, capacitors, diodes and a clock crystal,” describes Vondle.

The solution they initially came up with was to stamp 
a gap into the single piece of flexible stainless steel 
for the components to go into. However, with the discovery of photochemical etching, they happened upon a far better solution, which allowed for greater control of tolerances. In simple terms, the flexible com-ponents are placed into a 5 mm pocket etched into the steel band.

Although Vondle says that the whole project has been incredible, his favourite part was, after an eight-week wait, getting the display modules back from the manufacturer. “A good friend and fellow electrical 
engineer and I stayed up all night working on the code 
to get the clock working for the first time. It was both exciting and a major relief that everything was working well,” he smiles.

Their design process is markedly different to how wristwatches are traditionally made, but as Vondle says, this was probably to their advantage, especially as they weren’t designing for a specific gender.

“There is this bizarre male/female dichotomy of wristwatch design. Male watches have to be enormous and heavy whilst women’s watches have to be dainty. We are finding both men and women are attracted to our design and I think it has to do with us coming from 
outside the industry. We never assumed the watch had to be gender-specific,” he says.

They set themselves a goal of debuting a working prototype of the CST-01 at the Consumer Electronics Show 2013, which took place in Las Vegas at the beginning of January, and frantically worked towards it.
There’s been an enormous amount of interest in the watch already, which Vondle and O’Leary are thrilled about. “One of the sides to the watch is that it’s a kind of technological curiosity,” says Vondle.

“There aren’t many flexible E Ink displays on the market in any product, and nothing as thin as we have achieved. When people hold it, many stare at it for up to a minute because they don’t believe it is real and that the numbers will change. Something that elicits that kind of reaction works very well as a fashion object. Especially now with our mobile phones keeping very accurate time, watches have become even more of a fashion object.”

With the CST-01 shipping later this year, the product is currently in production. “We wanted production and assembly to be in the US to allow us to stay connected to the manufacturing process and prevent the risk of miscommunication,” explains Vondle. “Also, a part of doing this just comes down to wanting to keep jobs here in the US and keep the US making products.”

With their first product being such a success, does CST have another up their sleeve? “Well, we have already been talking about the CST-02, but there is still a lot of work to put into the CST-01 to make it the best product we can,” concludes Vondle.  

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