By mimicking the design of a spider organ, researchers have made a new sensor that's tiny, flexible, and sensitive enough to detect heartbeats and human speech.

The sensor, described Wednesday in the journal Nature, is inspired by an organ called the slit sensilla. These parallel slits, located near the joints of a spider's legs, can detect minute vibrations. When sound waves deform the shape of the slits, a signal goes to the spider's brain so they can sense the movement. In the species Cupiennius salei (known more commonly as the American wandering spider) this organ is an important part of the mating ritual: Males rustle leaves to get their mates' attention, and females detect the scratching using their slit sensilla.

This new sensor, which its developers hope can be used to detect speech and heart rates on wearable electronic devices, isn't quite as sensitive as the real thing. But it's designed with spiders in mind. From Live Science:

The new sensor consists of a platinum film on top of a soft polymer, with cracks in it, according to Mansoo Choi, a mechanical engineer from Seoul National University in Korea, and his colleagues. They call it the "‘nanoscale crack sensor."
Vibrations cause the cracks to stretch or compress, which changes the resistance of an electrical circuit.

Without vibrations, the platinum film lies flat, closing all the cracks. This keeps electrical currents running through the film. Vibration stretches the film, lifting the cracks open and blocking more and more of the electrical current. These signals can be interpreted in much the same way that the spider's organ motions can be interpreted by its brain.

In tests, the sensor was able to accurately record every note of a song played on violin, as well as simple words. The next step is remaking the sensor with cheaper materials like copper or aluminum instead of platinum. Science Magazine reports that the researchers hope to have it on the market -- doing the ear work for your Fitbits and smart watches -- within the next five years.