Visions of the future of medicine often involve digital sensors that constantly monitor patients, but not many people imagine that these sensors could be stitched directly into us. But that's the suggestion of a team of researchers from Tufts University, who have developed prototype "smart stitches" that can be used to close wounds — but also send real-time data on tissue health to doctors.
the stitches can monitor chemical balance as well as tissue strain
To make their stitches smart, Tufts scientists created a few basic thread types to act as building blocks for more complex sensors, as described in a paper published in the journal Microsystems & Nanoengineering. The two most important of these were threads that could transmit small amounts of electricity, made by dipping strings of cotton in conductive ink; and threads that would carry liquid through the tissue, created by giving the threads a hydrophilic coating that increased their capillary action (that's the same force that's in action when liquid soaks through a paper towel).
An illustration showing the current implementation of the threads (top left), and future uses. (Image credit: Tufts / Microsystems & Nanoengineering)
By combining these two threads with other materials, the scientists were able to create stitches and bandages with an array of different functions. These include gauging the amount of strain exerted on muscle (done by coating threads with a material that conducts more or less electricity based on whether it's being stretched), and measuring the pH, or chemical composition, of the tissue (done by wicking liquid from the wound to a sensor on the exterior of the skin). Other threads were created that measured glucose concentration, temperature, and pressure, and all the sensors sent their data to an external module that transmitted the information wirelessly to a computer.
sewing the sensors into the tissue means getting information quicker
All of this information is useful for doctors monitoring a patient's health. The pH of a wound, for example, is a good indicator of how it's recovering. The healing process is more effective in an acidic environment, but if the acidity becomes too high, it's usually indicative of a bacterial infection. This sort of information can be difficult to retrieve, even using smart sensors build into bandages. But because smart stitches would be embedded deep into the tissue, they could pick up on warning signs as soon as they manifest.
There's still a lot of work to be done on smart stitches before we can say whether they'd be useful in the real world though. Tufts' scientists only did limited testing of the smart threads in live tissue, and the sensors would also face scrutiny in terms of accuracy and reliability. Still, for an update to a medical technology that dates back some 5,000 years to the ancient Egyptians, making stitches smart could be a major step forward.