An Ultrasound That Sticks Around

Thanks to the introduction of smartwatches, we have grown used to the idea of wearing health monitors on our bodies. These watches frequently have sensors that can detect physiological parameters such as heart rate and blood pressure. Continuous monitoring of these vital signs has proven to be very useful, with many people having been diagnosed with conditions they were previously unaware of as a direct result of using the wearable. That, in turn, allows for early treatment to prevent serious symptoms from arising.

Now a team led by researchers at Duke University wants to up the ante in the world of health wearable tech. While basic vital sign measurements provide medical professionals with a lot of information, an ultrasound can give far more data. So the team developed a tiny, wearable ultrasound machine, no larger than a smartwatch, that can be stuck anywhere on the body to noninvasively collect continuous data.

Not only are traditional ultrasound machines bulky and expensive to use, but they are also tied to one location, so they cannot collect data as a person goes about their normal daily activities. This new device breaks down these barriers to enable new applications in monitoring athletic performance and rehabilitation progress. It can also keep tabs on other conditions, like skin cancer or the status of a healing wound, without a trip to the clinic.

The device is able to measure tissue stiffness at depths of up to a couple of inches beneath the skin. Stiffness is a critical biomarker in medicine, with changes often signaling the presence of disease or injury. For example, clinicians use stiffness readings to diagnose cancers, track wound healing, or evaluate muscle recovery after injury. Until now, capturing this information typically required an ultrasound system in a clinical setting.

The patch-sized sensor works by sending sound waves across the skin and then analyzing the resulting vibrations. Much like how knocking on a wall helps identify the location of a hidden stud, the device listens to the tones that return from the body. Lower-frequency sounds travel deeper, while higher frequencies reflect more superficial layers. By sweeping between 50 hertz and 800 hertz, the system can build a picture of both the skin and underlying tissue stiffness in real time.

The researchers’ prototype is battery powered, accessible wirelessly via Bluetooth, and currently lasts a couple of hours on a charge, although the team is already working on extending that to multiple days. Furthermore, it is lightweight, flexible, and able to stay in place even while the wearer moves around, making it suitable for continuous, ambulatory monitoring.

Looking ahead, the researchers envision integrating the patch into athletic gear, medical wraps, or even everyday clothing. Athletes could use it to optimize training sessions, spot fatigue before injury strikes, and fine-tune recovery schedules. Patients with chronic illnesses might wear it to provide doctors with continuous data, helping guide treatment decisions without repeated hospital visits. And as assistive robotics advance, exosuits could tap into the real-time stiffness readings to adaptively support muscles and joints.