Stretching the Limits of Wearables

Portable computing has progressed at breakneck speed over the past two decades, and that innovation has now given us even smaller devices that can be worn on the body. From smartwatches and fitness trackers to augmented reality glasses and smart jewelry, wearable devices are integrating cutting-edge technologies more deeply into our daily lives. With the ability to track vital signs, receive notifications, and control other devices, wearables are redefining the boundaries between humans and machines.

As advancements in miniaturization and battery life continue, the potential applications for wearable devices will only expand. But as it now stands, current technology is not particularly well-suited to many wearable applications. Water and high humidity levels, for example, can wreak havoc on traditional computing and sensing technologies. Furthermore, the components that make up these devices tend to be rigid for the most part, and that is not exactly compatible with the flexibility of the human body. More durable and comfortable options are needed before wearables will really be able to take off with mainstream users.

Recent work carried out by a team at The University of Hong Kong may pave the path to the development of more comfortable and robust wearables in the future. They have built on existing organic electrochemical transistor (OECT) technology, which is perfectly content working in wet or humid conditions, such as those that might be experienced by wearable devices. But since today’s OECTs are rigid, they developed a method that can produce a flexible version of them.

The novel OECTs are made of stretchable components that include an elastomeric substrate, a semiconducting polymer-based channel, and a solid-gel electrolyte. These transistors also feature gold-based source, drain, and gate electrodes. The OECTs are produced using a high-resolution inkjet printing system, which allows them to achieve impressive stretchability of over 50 percent, with sizes as small as 100 micrometers. That may be far from the nanometer-scale of traditional semiconductor-based transistors, but it is small enough to produce useful electronic devices.

To demonstrate the potential of their invention, the researchers developed an experimental device that makes use of the technology. Specifically, they created a smartwatch-compatible in-sensor computing module containing a stretchable array of OECTs. This module was proven to be capable of performing the signal processing required by a custom artificial intelligence algorithm. The OECTs were also able to detect raw electromyography signals from the surface of the skin with minimal interference from pesky motion artifacts.

This wearable was evaluated for its ability to predict the hand gestures of its wearer, and was found to have achieved an accuracy level of ninety percent. These results demonstrated the transistors’ potential for use in real-time, edge-based decision-making in wearable electronics.

This research will certainly not be the final word in the matter, but the team’s efforts do bring us one step closer to more practical wearable devices that can withstand the rigors of daily use.