The Challenges of Wearable ElectronicsNick Langston, Jr. – Head of TE’s Wearables Lab, Sr. Manager of Business Development and Strategic Partnerships, TE Connectivity
Wearable electronics have actually been used for decades in common medical devices like hearing aids, pacemakers and others. Consumer electronics such as cell phones and smart phones have even been adapted as wearables, with consumers wearing them as portable music players based on their need for function and connectivity on-the-go. Wearable electronics have evolved from life-saving devices to fashion accessories and range from activity monitor bracelets, smart watches and smart glasses to GPS enabled shoes—all of which have growing market demand.
Although the emergence of current wearable electronics stems mostly from consumer demand, there are a variety of wearable applications, including:
- Activity tracking
- Health monitoring
- Industrial and enterprise
- Soldier systems
Defining Wearable Electronics
A wearable device is one that turns power, data and sensing into insight. For example, one function of an activity bracelet takes raw data from a sensor, processes it and generates a report on the number of steps taken over a given period. Sensors track motion with enough intelligence to distinguish between steps and other movements.
Sensors are an important part of wearable electronics—you could think of a wearable simply as a sensor delivery mechanism—and continue to become smaller and more sophisticated. While there are many types of sensors that can be used, the most common is an inertial measurement unit – usually an accelerometer. An accelerometer can track a specific movement, its direction and its intensity or speed. One simple example of an accelerometer is when a mobile phone or tablet (the input) is rotated and the device processes the movement and rotates the screen accordingly (the output).
Other common sensors including pressure, temperature, position and humidity, support applications such as compasses, GPS and gyroscopes to detect movement. Sensors used in medical applications can be used to measure and monitor blood flow, pulse, blood pressure, blood oxygen levels, muscle movement, body fat and body weight. The most successful wearables are those that use algorithms to process raw, sensed data into actionable information for the user.
You could say wearables are where the IoT becomes the “IoMe”.
Wearable electronics must be able to communicate with the outside world. While wireless connectivity through short-range radio or other wireless protocols are popular, wired connectivity through a USB port is commonly required.
Many wearables have a video display or a touch screen for user interaction. A significant challenge for such small displays is ease of use. Even a high-resolution display on a smart watch doesn’t offer much real estate. Maintaining usability requires the right balance between how much can fit on the screen and how readable the resulting information is. Managing the power consumption of these displays is a major motivator for leading wearable manufacturers. They make wide use of low power alternatives like e-ink or e-paper as opposed to full color LCD or OLED displays. As with any electronic device, wearables must be powered by rechargeable batteries or other charging methods. This commonly requires a port for connected power to recharge the batteries. Wireless power transmission is emerging as a key feature to be integrated in new wearable devices, and offers the possibility of waterproofing devices.
Another common hallmark of wearable electronics is the ability to run a variety of applications while an app is updated or changed. A smart watch, for example, is similar to a mobile phone. It is a computer that enables the wearer to perform a variety of tasks while connecting independently to the Internet for critical app updates and downloads.
Wearable Electronics and the Internet of Things
Wearable electronics are a subset of the Internet of Things (IoT). It’s where the IoT meets the consumer in a highly interactive way. You could say wearables are where the IoT becomes the “IoMe”. One example is the use of a smart phone or watch to remotely unlock a home, control the thermostat and either arm or disarm a security system – from anywhere in the world.
IoT can also function without human intervention. A smart watch can be pre-programmed to turn up the heat on cold mornings and turn down the heat at night, or check the forecast and then adjust house temperatures based on that information. Additionally, sensors embedded into textiles—your bed sheets for example—could sense your body temperature and communicate with your smart thermostat to maintain the ideal sleeping environment.
Internet Protocol Everywhere: The Key to IoT
The key factor in IoT is the use of Internet Protocol (IP). IP is a communications protocol used by Ethernet and the Internet to control the flow of information. Every connected device has an IP address. Every device with an IP address has the capability of communicating with every other IP device.
Firewalls, passwords and other security measures control what devices communicate with each other. Wearable electronics, by virtue of an IP address, join the IoT.
One advantage to being part of the IoT is that wearable electronics do not have to exist as standalone devices. Activity data from a fitness bracelet can be downloaded to an app on a computer. This app can provide a detailed analysis of trends over time in order to track progress. The music player in a watch can retrieve songs using cloud computing (“the Cloud”). The end result is that people everywhere can interact with things – TVs, homes, cars, appliances and life-saving devices – as a result of a small device, held close to, or on our bodies – just by delving into the world of wearable electronics and the IoT.
Small is Beautiful: Packaging Challenges
Wearable electronics are enabled by the miniaturization and integration of components, which allow powerful functions to be packed into a very small space. Sensors, computer chips, cameras, speakers and other components continue to grow smaller while becoming more capable.
Packaging these components into the right form factor and the right level of manufacturability is a challenge. TE Connectivity works closely with designers and manufacturers of wearable electronics. Figure 1 shows typical connector solutions for a smart watch. The key feature for most of these, as well as other components, is a low profile with a small footprint. Low profile is especially important to allow the device itself to assume a slim design.
With real estate at a premium, the integration of parts not only simplifies the system, but uses available space to maximum efficiency. Antennas can be embedded directly into the housing for a mobile phone. Such Molded Interconnect Devices (MIDs) and emerging printed antenna technologies allow circuit traces, ground planes, and shielding to be integrated into molded parts. The substrate can be either an engineered plastic or a composite. Composites become increasing attractive in their ability to increase material strength and can be cost-effectively molded and metalized.
Making It Rugged
Many wearable systems are designed to be worn during sports and other rugged activity. Ruggedness as a concept is relative and can only be defined in terms of the application. The ruggedness requirements for a heart monitor are different from those of an activity monitor worn by a cyclist. Soldier wearables operate on an entirely different level of ruggedness, requiring wider temperature ranges, better shock and vibration resistance and resistance to chemicals or solvents that would ruin a consumer device.
Making wearable electronics more resistant to environmental hazards will make devices more reliable and easier to use. You can achieve a certain degree of weatherproofing by using a splash-proof USB port and rubber cover, but this does not make the device waterproof. Designers are looking to close openings in devices to achieve IP67/68 sealing for a waterproof design. Ingress Protection (IP) is used to specify the environmental protection of enclosures around electronic equipment. Not only does waterproofing yield a more robust design, but it promotes easier use. Some approaches, like wireless power transmission, are emerging in the market.
Magnetically Attached Cable: USB and similar connectors use a friction fit to keep connectors mated. An alternative approach uses magnets to hold the connector in place with spring- loaded contacts on the cable side. Device-side contacts and magnets can be sealed to prevent liquids and moisture from entering the device. As opposed to mating micro USB connectors, the magnets help pull the cable into proper position.
Packaging these components into the right form factor and the right level of manufacturability is a challenge.
Contactless Data Connections: Magnetic attachments and transceivers in both the device and cable assembly create a wireless connection. This approach can support high-speed I/O protocols such as USB 2.0 and 3.0. The short distance between transceivers provides a power-efficient and inherently secure connection.
Wireless Charging: Batteries can be charged without a direct electrical connection. Wireless charging, or inductive charging, uses induction coils in the charging unit and electronics to charge the device. The electromagnetic field created by the charging coil allows energy to be transferred to the receiving coil, acting like a transformer. The advantages of wireless charging include:
- Increased durability: no wear and tear to connectors
- Increased reliability: no connector port providing entry for contaminants
- Easier use: no small connectors to mate
- Design freedom: industrial designers are free to create new, unusual forms for devices
- Longer life: building power transmitters into common objects means devices charge continuously
Current drawbacks to wireless charging can include lower efficiency, higher heat generation and slower charging. Each of these issues are related and will be improved by newer coil structures and higher coupling frequencies. Most wearable devices are extremely low-powered, meaning the impact of these drawbacks may be minimal.
Smart Textiles and Electronic Clothing
Another trend in wearables is to embed sensors and electronics into textiles, from specialty athletic wear to everyday clothing. The challenge is to create electronic clothing that can be both manufactured and treated like other clothing, being comfortable, flexible and washable. Most importantly, the products must be fashionable. In order to support designs that consumers would be comfortable wearing, the interconnections and electronics must be unobtrusive and robust. This requires:
- Reliable terminations that are insulated, robust and waterproof
- Flexible, garment-based antenna and transceiver solutions
- Stretch-conductive insulated wire
- Small, dryable batteries
- Crease and crimp resistant PCB/FPCs
The electronic wearable market’s challenge is to create devices that can offer useful data that will improve our lives. Whether worn on the wrist, head or foot, wearables must be fashionable, rugged and easily rechargeable.
For more information on TE’s product offering for consumer wearables and hand held devices, click here.