The human body withstands a multitude of harsh conditions, from high temperatures to chilling winds, and from submersion in water to rigorous exercise. Our bodies enable us to satisfy our yearnings for adventure, while helping us survive in constantly evolving environments.

Also, thanks to the inventiveness of the human brain, we’ve now got access to a multitude of wearable technology that’s adept at supporting us, both with day-to-day and health-related tasks, and as we undertake ever-more-daring endeavours.

When you say ‘wearable technology’, many of us think of products such as wristband step-counters and smartwatches that have risen to prominence in recent years. However to find the very earliest wearable tech, you actually have to go back rather further to around 1286. This is about the time the eyeglass was invented. Fast-forward to the 19th century, and you will come across other wearable tech creations, such as the air-conditioned top hat and an electrically lit dress.

But of course, the real boom in wearables has happened since the turn of the millennium – and it hasn’t all been about fitness trackers. A collaboration between Levi Strauss & Co. and Philips led to the ICD+, which was a jacket with a built-in wire harness that linked up various portable electronic devices. It included a Central Control Module (CCM) to connect and operate the wearer’s mobile phone, MP3 player, and headphones. As far as its technology capabilities are concerned, the coat needed to be a functional and fashionable garment that could keep the wearer warm, while being breathable to help cool them if they got too hot.

Today, wearables are all around us, with over 170 million wristwatch devices expected to be sold in 2020. Whenever we strap on our Apple Watches or Fitbits, we are asking technology to go wherever we go. We are expecting it to be able to stand up to whatever we do, and operate in locations that may once have been too challenging for either humans or electronics to withstand. As a designer, this poses a variety of significant challenges.

Few things are more punishing than extremes of heat or cold. Death Valley in California is officially the hottest place on Earth, with temperatures of 56.7°C recorded in 1913. This is beyond the limits in which humans can survive. Even today, the area often gets up to 47°C in the summer. Given all of this, it’s astonishing to think that humans have decided to challenge themselves to what’s billed as ‘the world’s toughest footrace’ in this very location: the 217km Badwater Ultramarathon. Many don’t finish, and even the fastest runner in 2018 took more than 24 hours. While it has thankfully claimed no fatalities in its 30-year history, it is regarded as one of the toughest tests of human endurance.

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Figure 2: Far more than an accessory, wearables present opportunities for monitoring the human body.

Any technology that the runners take with them must be capable of withstanding the extremes to which it will be exposed. The combination of sweat, heat, sand, pressure, and regular impacts is the ultimate environmental testbed for wearable tech.

For designers, the key is to ensure their device retains both its form and its function, while keeping weight and size in check and making sure the interface is easily usable. Even a device as straightforward as a step-counter must have a screen that’s readable in bright sunlight, a strap that doesn’t erode when exposed to grit and sand, and buttons that work even when coated in sweat or grime. Also, the internal components need sufficient protection from dust, fluids, and anything else that may try to work its way inside.

These ultramarathon runners may be pushing their bodies to greater extremes than most people, but that doesn’t mean the wearable tech used by the wider population gets an easy ride. Even just going about your daily routine will be putting pressure on your body and any technology attached to it.

If you wear a fitness tracker round your wrist, for example, you will probably have it on whenever you wash your hands. This will mean it regularly gets splashed with water. This is something engineers need to design for, by providing at least some degree of water-resistance in their products, even if they aren’t fully waterproof. Think about the creams, aftershaves, fragrances, and other cosmetics we use, which can gradually clog up a device’s sensors or openings. Consider the number of times the device is knocked, as you reach into cupboards, pick up your children or do the shopping.

When you go to the sports centre and sweat your way through a tennis match or fitness class, your tracker needs to come through unscathed. This poses significant challenges for engineers. For example, consider the heart-rate monitor: how do you place a photodiode detector and LED assembly close to the body, without it getting clogged with sweat and dirt?

Professionals who work in extreme environments now use technology to help stay safe and monitor their health. Military pilots, deep sea divers, and scientists working in the coldest parts of the world depend on technology to help them survive. For example, the forces that air force pilots can experience daily – and the effects thereof – can be monitored by wearables, which at the same time must be able to withstand these forces themselves.

Researchers have identified exactly how much acceleration our bodies can cope with: 14g of lateral acceleration is beyond the limit we can withstand. Knowing where the limits are helps ensure things like air travel remain within safe levels. After all, we expect our bodies and our technology to continue operating normally in the air, despite changes to pressure, temperature and position. Also, when we step off the plane in New York, we want everything to work just as it did when we boarded in San Francisco.

It’s been shown that most people will suffer from hyperthermia (our bodies overheating) and not survive more than about 10 minutes when humidity reaches extreme levels or the temperature hits 60°C. But at the other end of the spectrum, the limits of our ability to withstand cold are more difficult to define. A human will generally expire when their body temperature goes down to –21°C. But the speed at which we get to this point can vary, depending on whether the individual is used to very cold temperatures, and whether they enter a state of hibernation.

People living and working in the coldest settlements on the planet, such as Fairbanks in Alaska, have developed ways of coping and equipment that helps them function properly. With the minimum average temperature –27°C, the climate at Fairbanks provides an incredibly hostile environment for its inhabitants and their technology, with specialised equipment sometimes required because ordinary consumer kit simply isn’t designed to operate at these extremes. The manual for the latest-generation Fitbit Charge 3, for example, gives –10°C as the device’s minimum operating temperature. The mitigating factor for wearables, of course, is that because they are operating close to the body, the body’s heat will generally help keep them warmer in cold conditions.

To enable humans to work and play in such cold environments, engineers have created sensors that keep tabs on the wearer’s temperature, providing an alert if there’s a dangerous shift. From the designer’s perspective, there’s more than just the sensor to think about. Other considerations must include the facts that some batteries stop working below –30°C, and that many LED-based displays have a limited temperature range in which they can operate. So, as humans continually strive to live and work in more difficult conditions, those designing the equipment that accompanies them need to keep pace.

These types of health-monitoring components are also used in regular consumer gear, such as battery-powered clothes that keep you warm and safe, perhaps when hiking or mountaineering. The drawback, of course, is the need to take enough batteries to last the duration of your trip, at which point weight may become an issue.

Whatever you do, don’t make the mistake that many people do of throwing everything – including their wearable tech – into the washing machine! A quick web search will show just how common this is, bringing up plenty of questions on how to get a fitness tracker, smartwatch or headset working again after it’s inadvertently been through the wash – an environment that for some devices will be a step too far in terms of extremity.

Another group of people continually pushing their bodies’ limits are athletes. How much faster can they run? How much longer can they perform for? How much higher can they get? To monitor these things and more – and receive constant feedback – they can use wearable tech.

Take American football as an example, where technology is helping improve player safety. Reebok and MC10 have released a skullcap that measures the force on a player during a hit or tackle. The reading from the device then helps the medical team decide whether the player is likely to need checking for concussion. To help protect players in this way, the skullcap itself must of course be able to withstand very significant forces.

Location-trackers can be sewn into athletes’ clothing to provide real-time data on players’ speed, balance, movement, and acceleration. Information gathered from these sensors can be analysed to help identify early signs of soft-tissue injuries, enabling the coaches to proactively withdraw players before injuries get more serious. Sensors like these need to be extremely lightweight and unobtrusive, as well as being able to tolerate friction, impacts, motion, and sweat – all of which they will be exposed to during a game.

Of course, these kinds of innovations aren’t limited to professional athletes. Anyone who enjoys running can put sensors in their socks or shoes to monitor their technique. Via their smartphone, they can see how their feet are striking the ground, enabling them to adjust how they run to improve their speed and/or the long-term safety and wellbeing of their bodies. Technology such as this makes running more of a science than ever before.

So having seen how far wearables have come in recent decades, what does the future hold? While predictions and inventions don’t always coincide with what consumers actually want, what is clear is that there’s a growing desire to track, monitor, and record our every movement. Could future wearables harness some of the energy from our movements, and use it to power sensors, or even provide warmth or cooling for the wearer? Could we pop in contact lenses that incorporate displays, enabling us to view our calendars and plan our time, without needing to look at a computer or smartphone? The future could include all, some or none of the above, but what is likely is that whatever extreme we as humans push ourselves to next, wearable technology will be with us for the journey.

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Figure 3: According to statista, the global wristband unit shipment is projected to reach over 51 million by 2022.

Mouser Electronics

www.mouser.com