Engineers have designed a thin adhesive film that could upgrade a consumer smartwatch into a powerful health monitoring system. Smartwatches can already help keep track of how far the wearer walks and sleeps and monitors heart rate; newer models monitor blood pressure. Working with a tethered smartphone or other devices, someone can use a smartwatch to keep track of those health indicators over a long period of time.
What these watches can’t do is monitor body chemistry. For that, they need to track biomarker molecules found in body fluids that are highly specific indicators of health, such as glucose and lactate, that tell how well the body’s metabolism is working.
To address that need, the researchers engineered a disposable, double-sided film that attaches to the underside of a smartwatch. The film can detect molecules such as metabolites and certain nutrients that are present in body sweat in very tiny amounts. They also built a custom smartwatch and an accompanying app to record data.
There are more than 100 million smartwatches and other wearable technologies sold worldwide that have powerful data-collection, computation, and transmission capabilities. The new film upgrades these wearables into health monitoring platforms, enabling them to measure molecular-level information so that they provide a much deeper understanding of what’s happening inside the body in real time.
The skin-touching side of the adhesive film collects and analyzes the chemical makeup of droplets of sweat. The watch-facing side turns those chemical signals into electrical ones that can be read, processed, and displayed on the smartwatch. Making the sensors on a doublesided adhesive and vertically conductive film eliminated the need for external connectors and the effect of a user’s motion that can interfere with the chemical data collection.
By incorporating appropriate enzymatic-sensing layers in the film, the researchers specifically targeted glucose and lactate, which indicate body metabolism levels, and nutrients such as choline. While the team designed a custom smartwatch and app to work with the system, the concept could someday be applied to popular models of smartwatches.
The researchers tested the film on someone who was sedentary, someone doing office work, and people engaged in vigorous activity, such as boxing, and found the system was effective in a wide variety of scenarios. They also noted that the stickiness of the film was sufficient for it to stay on the skin and on the watch for an entire day without the need for a wrist strap.