Super-Stretchy Strain Sensor Could Upgrade Human Motion Detection

Researchers developed a new strain sensor with atypically high stretchability, efficiency — and is also sensitive to motion-related changes in the surrounding environs, according to a new paper published in Elsevier's journal Nano Energy.

The new device can also self-heal because it's composed of conductive and ionic poly(acrylamide) (PAAm) hydrogel — which allows it to self-repair when damaged or torn.

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Super-stretchy strain sensor, motion detection

Strain sensors are interesting machines capable of converting force, tension, weight, and pressure into electrical resistance (also called capacitance) — which is then measured and quantified. In the last several years, the sensors were used to invent a plenum of devices capable of detecting motion in their surroundings like health monitoring devices, robots, and smart human-machine interfaces.

The researchers collaborated from Fudan University, Tongji University, and the Chinese Academy of Sciences.

"The ionic conductive PAAm hydrogel shows an excellent self-healing property with fast electrical self-healing speed (within 1.8 s[econds]) and high self-healing efficiency (99%) ," wrote the researchers in their new paper. "The PAAm hydrogel-based strain sensor exhibits excellent performance with large stretchability (>900%), high sensitivity (with maximum gage factor of 6.44), fast response time (~150ms) and good cycling durability (>3,000 cycles)."

Strain sensor tracks human motion in real-time

The researchers' new strain sensor was made to monitor numerous human motions in real-time. When used with silicon integrated circuits, it then transfers recorded data directly to smartphones, or other smart devices, via Bluetooth.

This allows the device to continue tracking human body motions — a useful trick for health and fitness tracking tools. To show off its wireless detection capacities, the researchers wired one of the new sensors to a printed circuit board, then stuck it on a human joint to record motion data.

Motion detection of human gestures

The device's recorded data was converted into a digital signal that was controlled via an Arduino Nano microcontroller board before it was transmitted via Bluetooth, to a smartphone. Finally, the data was displayed on a Kivy-developed app.

The new device also offers the ability to create technology that correctly perceives human gestures. For example, the researchers made a smart glove integrating five of their sensors on each finger to record data about a user's hand motions. This in turn is analyzed and interpreted via computational models, reports TechXplore.

As of writing, this strain sensor device has already shown impressive potential for a wide scope of novel applications like interactive robots, fitness trackers, human-machine interfaces, and health monitoring systems. Someday, it might even become the basis for several novel smart devices using advanced motion detection capabilities.