In the computing revolution that started with the invention of the transistor in 1947, microprocessors have continuously become faster, cheaper, and more energy efficient. These improvements have shrunk the typical computing device down from the size of a room into a phone that fits into the palm of your hand. The next step: something that fits onto our wrist or attaches like a piece of jewelry onto our clothes or bodies. The era of wearable computing is emerging, and the only thing holding it up is batteries.
The typical consumer device battery is made up of rigid electrode plates surrounded by a gel or liquid electrolyte that needs a lot of non-flexible packaging to keep the outside air from getting in and the potentially flammable internal materials from getting out. All that rigidity makes for very few options in designing a battery that is capable of meeting the ever increasing power needs of wearable devices. In fact, if you look closely at most wearable devices today, including the Google Glass and the Jawbone Up, they are designed around a battery that can’t bend or conform to the shape of the device, while the other parts of the device — including the microprocessors, accelerometers, and other active components — are much more flexible in their design parameters.
Slim and Powerful
Now that the wearable computing industry is demanding better and more flexible batteries, the battery industry is responding, and for good reason. Navigant Research’s Advanced Batteries for Portable Power Applications report forecasts that the market for batteries for wearable devices to grow from $62 million in 2014 to $795 million in 2023. Two large battery manufacturers have begun to build customized manufacturing lines expressly to make smaller, more power-packed, and more flexible batteries for wearable computing devices, and at least four battery startups are expressly targeting the wearable device industry with new battery chemistries and designs. One of them, Imprint Energy, believes that its zinc-based chemistry lends itself to very slim and flexible battery designs.
And then there are the laboratory experiments. Many electrochemistry laboratories are trying to design novel batteries for the wearable computing industry that meet its three fundamental needs: energy density, durability, and safety. One of the more promising developments comes from the laboratory of James Tour at Rice University, which developed a thin-film nickel fluoride battery that has shown impressive durability. Other interesting projects involve weaving battery electrodes into a yarn-like structure that can be sewn right into clothing, such as is being done here and here. While such textile-like batteries might eventually prove very promising, it’s hard to imagine that a shirt made out of battery components would be very popular clothing choice, due to the risk of sweating next to a surface with an electrical charge running through it. However, a textile-like battery that is properly enclosed in safety packaging could provide the necessary flexibility and conformability for which wearable computing manufacturers – and potential buyers – are clamoring.