A team of South Korean scientists has developed a skin-attachable sensor that can continually measure blood pressure without the traditional inflatable cuff, a finding that researchers believe could address long-standing accuracy worries about smartwatches and other wearables. 

The technology was developed by Dr. Shin Hur and his team at the Korea Institute of Machinery and Materials (KIMM) and experts from the Korea Institute of Science and Technology (KIST). Mechanical engineering, materials science, and biological sensing are all used together in this project. 

An ultrasound machine is unique because it can directly measure changes in the thickness of blood vessels under the skin. Because arteries can get wider or narrow, blood pressure changes. You don't have to squeeze the arm to get the systolic and diastolic pressure from the monitor. It does its job by seeing these little changes as they happen. 

These days, most machines that don't need a cuff measure blood pressure by looking at changes in the way light moves through the skin. These measures can be off because of things like your skin colour, how mobile you are, the lighting, and the depth of your blood vessels. Because of this, a lot of customers and pros aren't sure how reliable these systems are.

On the other hand, doctors use ultrasound to take pictures of organs and blood flow right now. It puts sound waves into the body and listens for echoes, to put it simply. The new sensor miniaturises this idea into a flexible patch that is less than half a millimetre thick and weighs less than one gramme, allowing it to stay on the skin for extended periods. 

The device is powered by PMN-PT, a highly sensitive piezoelectric material that converts electrical energy into sound waves and back again. Using a low-temperature soldering technique, the team placed an array of ultrasonic transmitters and receivers onto a bendable base without affecting their performance. 

The sensor was tested on an artificial blood vessel model that resembled human skin and arteries. The results were within the AAMI clinical standard for medical-grade blood pressure devices, with systolic and diastolic pressure errors of ±4 mmHg and ±2.3 mmHg, respectively. 

"This technology is the first to demonstrate continuous, cuff-free blood pressure monitoring using a skin-attachable ultrasonic sensor," Dr Shin Hur, of KIMM, said. "Combined with AI-based blood pressure analysis, it will evolve into a core platform for personalised cardiovascular disease prediction and smart healthcare." 

Researchers believe the technique could serve as the foundation for future wearable health systems, providing readings comparable to those obtained in hospitals while being comfortable enough for daily usage. While more clinical testing in humans is required, the findings indicate a potential move away from estimation-based wearables and towards direct, physics-driven monitoring.