The Fascination of Technology Sensor Patch Uses Octopus Trick to Measure Heart Rate

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In our “Fascination with Technology” section, we showcase impressive research and development projects for engineers every week. Today: a smart patch that, thanks to a clever octopus-inspired trick, adheres perfectly to the skin and measures heart rate and arterial stiffness for cardiac diagnostics more accurately than any smartwatch.

A research team at the Norwegian University of Science and Technology (NTNU) has developed an innovative patch that can measure heart rate and vascular stiffness—without any electronics at all. When combined with a standard smartphone camera, this invention—which draws on a clever trick from nature—could revolutionize healthcare.

The Octopus as a Role Model

For this unassuming patch, made of silicone rubber, to measure reliably, it must conform like a second skin. Here, the researchers drew on bionics: they modeled the design after octopuses. The underside of the patch features a special three-dimensional structure that is modeled exactly after an octopus’s suction cups. This biomimetic surface ensures that the patch adheres extremely firmly and securely to human skin, which is what makes precise measurement possible in the first place.

We wanted to develop a flexible, affordable device. What makes it unique is that we can see the heart's signal on the patch with our own eyes.

Angelos Xomalis, associate professor at NTNU

The top of the patch, on the other hand, shimmers like the back of a CD. Its secret lies in a nanoscale pattern. “We wanted to develop a flexible, low-cost device. What makes it unique is that we can see the heart’s signal on the patch with our own eyes,” explains Angelos Xomalis, associate professor at NTNU. As soon as pulse waves from the blood vessels cause the skin to move, the patch expands. These mechanical movements cause immediate color changes on the surface, which can be captured by any standard smartphone camera. No additional equipment, such as spectrometers or lasers, is required.

More Accurate and Fairer than Smartwatches

The invention offers significant advantages over conventional fitness trackers. Smartwatches typically use optical sensors (green LEDs) to measure changes in blood volume. “One drawback of smartwatch measurements is that they are heavily influenced by skin pigmentation and work less effectively on darker skin,” says Xomalis. This is a significant problem for equitable healthcare. The Octopus patch completely circumvents this problem, as it operates purely mechanically.
It also provides deeper medical insights. It measures not only the pulse but also the stiffness of blood vessels. “Blood vessels generally become stiffer with age. In heavy smokers, they often age even faster, while athletes can maintain a younger vascular system,” explains Torjus Lines Steffensen, a postdoctoral researcher at NTNU. Stiff blood vessels are an important indicator of cardiovascular disease—information that conventional smartwatches cannot provide at this level of detail.

High-Tech Medicine for Remote Regions

Until now, such precise measurements have required expensive ECG machines that are tied to hospitals or doctors’ offices. However, the researchers emphasize that in remote parts of the world, such as Africa, access to such infrastructure is often lacking.
The new patch solves this problem: It simply shifts the technical complexity of the measurement to the smartphone—a device that is already available almost everywhere in the world today. In initial clinical trials, the technology has already proven so reliable that it outperformed established methods. The NTNU researchers therefore view their development as the starting point for a completely new generation of portable, low-cost, and battery-free health sensors.
 

Source: Advanced Materials, doi: 10.1002/adma.74512