Human beings are very efficient biological machines. We run on a similar amount of power to laptop, which is quite impressive when you consider all the thinking we do and all of our constant movement. It is likely that we evolved to be bipedal because its efficiency allowed us to perform persistence hunting. It would be nice if we could spare a little bit of our efficiency to power our electronic devices and this new magnetic patch may make that possible.
Material, such as iron, becomes a permanent magnet when its atoms' electrons align. You can magnetize iron by aligning the atoms using another magnet, but you can also do so using electricity. An electromagnet uses an electric coil to create a magnetic field, which aligns the core's electrons. The opposite is also true. Moving a magnet through an electric coil produces a current, which is how a Hall effect sensor works. The generated current is small, but a team of UCLA engineers were able to put it into practical use.
This "magnetoelastic" patch take advantage of the Hall effect in order to generate a power, which is useful for wearable sensors. It resembles a nicotine patch, but with microscopic magnets lining a thin, flexible silicone matrix. As the patch twists, stretches, and flexes on the wearer's skin, the Hall effect comes into play. In testing, the patch generated up to 4.27 mA per square centimeter of material. Even at 5V, that would be a very small amount of power. But it is enough for many types of sensors, which makes this magnetoelastic patch ideal for medical wearable monitors. The patch itself could even act as a sensor. For instance, it could product an electric current that correlates with the wearer's pulse.
We've seen other patches that generate electricity, but this is the first that relies on magnetoelastic material.