The new technology

Investigating the range of footwear applications for 21st century science.

by Stuart Morgan

The ability to wear the latest technological advancements has proved fascinating to many people around the world. Perhaps the earliest example of ‘wearable tech’ was the hearing aid, with the first electric version being invented in 1898. While gradually getting smaller, these units remained bulky for decades until the creation of the microprocessor in the 1970s. The calculator watch was marketed soon after this breakthrough and became one of the first widely adopted pieces of wearable technology. In recent decades, we have seen the launch of a wide variety of innovative products, such as ‘smart’ watches, fitness trackers, smart glasses and virtual reality headsets. Some of them have proved to be great successes, whereas others have quickly been withdrawn from the market as dismal failures.

In recent years, an increasing number of footwear manufacturers have invested in the development of ‘smart shoes’, which are marketed as incorporating technology for a number of specific applications.

Power generation

One such achievement has been the ability to use the energy that is normally lost as heat while walking to generate power – known as ‘energy harvesting’ – by exploiting the motion between coils and magnets. A number of ideas of how this could be done have been revealed. As an example, some years ago German researchers developed ways to produce power from two separate devices: a ‘shock harvester’ that acts as a generator when the heel strikes the ground, and a ‘swing harvester’ that produces power during the swinging phase of a step.

Another design saw an embedded mechanical system inside the shoe soles generating kinetic energy during the heel strike of each step. This energy was used to spin a micro-generator that in turn charged a battery pack, either clipped to the laces or worn around the wearer’s ankle. Once the battery pack was fully charged, it could be unclipped from the shoe and connected to a device via a USB cable. A one-hour walk was said to generate two-and-a-half hours’ worth of power for a smartphone.

One developer anticipates possible power output to be up to 2.4 watts, with 1 watt of energy available continuously at a normal walking pace of 5km/h (3.1mph). Markets for such footwear-based power generators include commercial work boot, sports shoes and military footwear, providing the wearer with an off-the-grid capability to charge portable electronic device batteries as they walk. Alternatively, direct and immediate power can be provided to such electronics as footwear heaters or GPS locators without the need for batteries.

Fitness trackers/ performance monitors

For many years, wrist-worn fitness trackers and smart watches were used to monitor various kinds of exercise data. However, since 2016 a number of special smart shoes have been introduced to provide this function. Most modern fitness devices are claimed to record key running characteristics such as pace, cadence, calories burned, distance covered, stride length, swing speed, ground contact time, foot impact force, impact force on knees, landing zone, balance, pronation, hip tilt and vertical oscillation. After a run, these shoes can be linked to a smartphone app, which compiles the data and highlights if the wearer is landing harder on one foot and whether impact concentrates on the heel rather than the mid foot or toes.

Another smart shoe has an ‘auto start’ feature which automatically recognises when the shoe is being worn on a run, and has technology that begins to work once a speed of 11 minutes per mile is exceeded. According to the designers, such tracking stops when the wearer is not running, to ensure optimal battery life (which is claimed to be longer than the life of the actual shoe). An additional feature alerts the wearer once 400 miles has been run and advises that the shoes should be replaced.

Some companies have developed smart insoles that are designed to be placed underneath regular insoles within sports shoes. Built-in sensors transmit running performance and technique data to lightweight hubs (also said to be water-resistant) that attach to the outside of the shoes. This particular product is reportedly capable of detecting asymmetry in real-time, providing an insight on how to run more efficiently with greater balance and fewer injuries.

Running is not the only activity for which smart footwear has been developed. Technology-enabled golf shoes are being marketed to help players improve their game. Rather than providing running data, these shoes measure balance, pressure distribution and weight shift information. They are said to highlight mistakes and indicate ways to improve via a smartphone app. Waterproof sensors are designed to detect slight changes in the pressure distribution in a matter of milliseconds. These units can communicate via an app, which features a number of capabilities, including a professional swing library, to help track progress.

Inbuilt GPS systems

Smart devices on the market can even be smaller than an insole. One producer has developed ‘pods’ that are said to make any footwear smart. These items can be slipped into insoles that have been trimmed for fit and so can be worn with any shoes. As an alternative, the pods can be worn on the laces with a dedicated buckle. While these devices offer information on the number of steps taken, calories burned and distance covered, they do not produce advanced running metrics. However, they do provide GPS navigation by ‘haptic’ communication, meaning that the wearer can set his or her chosen route, and the smart shoes will thereafter act as a guide by producing left and right foot vibrations and patterns to indicate the direction to be taken.

Other GPS-enabled smart insoles are marketed under the umbrella of ‘assisted living technology’. These allow the monitoring of wearers who may have a tendency to wander or who are at risk of becoming disoriented and lost – for instance, as a result of Alzheimer’s disease, autism, dementia, traumatic brain injury or another cognitive memory disability. Their location can be tracked through a smartphone, tablet or web browser, and the software can send text and email alerts if the shoes leave or enter defined areas on a map.

A similar product was launched in 2014 In India. This incorporated smart technology in which shoe insoles were connected to a smartphone application running Google maps. The insoles vibrated to tell wearers when and where to turn to reach their destination.

A company designing GPS systems within footwear is working on an indoor navigation system. This uses sensors within the shoe to measure foot acceleration, angular velocity (which way the wearer is turning), and the magnetic field. According to the designers of this device, data from these sensors could be used to calculate how far the wearer has travelled and in which direction. A suggested application is for rescue teams who could track their movements in unfamiliar buildings on hand-held devices.

Injury prevention monitors

Obviously, the wearable footwear technology developed for runners can have a role in avoiding injury. However, there are other applications that are helping with specific health problems, one example being diabetes. A recent report stated that one-third of the estimated 3.7 million diabetics in the UK will develop serious issues including deformities, infections, gangrene and ulcers because they cannot feel pain in their feet. As a result, these sufferers do not notice the development of blisters, bruises or small cuts, which can result in the previously-mentioned conditions. The Diabetes UK organisation estimates that such problems lead to some 6,000 amputations each year.

One US-based company has developed pressure-sensitive shoe inserts which connect to a smart watch. These are said to provide real-time alerts when dangerous levels of pressure threaten to cause permanent damage to the foot. This permits the wearer to actively move weight off the affected area and so avoid the development of pressure ulcers. Following a recent study conducted over several months, the company reported that no ulcerative events occurred while their device was being used. According to the report, this suggested that the inserts assisted in preventing pressure-related injuries to the affected foot. One patient also reported that the alerts offered by the device allowed him to think less about avoiding pressure on his heel at all times.

Controllable heating

Designers have investigated several ways to provide adjustable heating for footwear. One company’s method involves using rechargeable lithium-ion batteries encapsulated in an insole. These provide power to a far-infrared heating element placed beneath the toes (said to be the part of the foot most susceptible to the cold). On-demand heat – continuously for up to six hours per charge – is controlled through either an approved frequency remote control or a smartphone app.

The provision of heat to the foot also has a health benefit, as it can bring relief to sufferers of Raynaud’s Disease (a medical condition in which artery spasms cause episodes of reduced blood flow) and mild arthritis by helping to increase blood flow and keeping extremities warm. A charger socket is located in the back of the heel of the insole, and a remote control keychain is supplied to switch the heat on or off, or to change heat settings. These particular insoles are available in four sizes, and can be trimmed to fit the wearer’s shoe.

Secure identification

Recent reports suggest that a laboratory in the USA is working on shoe insoles that can help to monitor access to high-security areas, such as military bases or nuclear power plants. The concept is claimed to be based on research indicating that everyone has unique ways of walking. Sensors in the soles apparently check the pressure of feet, monitor gait, and then compare these patterns to a master file kept for that specific person. If the patterns do not match, a warning will be given.

The company designing these insoles says that an accuracy rate of more than 99 per cent has been achieved in existing trials, and tests are to be broadened out to include ‘a full spectrum of society’, including subjects who are athletic, heavy, tall or thin. It is claimed that the system ‘knows’ a person by his or her third step. While gait can be affected by injuries, fatigue and other factors, the designers claim that it can detect these problems, and thus make allowance for them.

Other applications

This article does not cover every possibility by any means – the application for wearable technology in footwear is open to the imagination. Even now, designers are working on – or have released – shoes that have internet access, give a massage or provide stimulation to the nerves on the foot, store music or offer automatic fastening. What will the future hold? Recent history suggests that not all of these wonderful ideas will work, but some will be successful and sell well. We will just have to wait and see.

SATRA’s contribution

SATRA has considerable expertise in testing both the durability and suitability of these types of technologies when they are incorporated into footwear. Such footwear presents its own unique problems when electronics are introduced, such as attacks from perspiration, flexing and harsh environments, as well as the necessity to provide comfort and meet specific legislation relevant to electronic equipment. Members with current devices, or who are planning to use such technology in footwear, or are approached by third parties are encouraged to contact SATRA for independent advice, testing and assistance with integration. We can validate commercial claims for features in specific products.   

Publishing Data

This article was originally published on page 8 of the November 2017 issue of SATRA Bulletin.

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