If robots are ever going to interact with us on a daily basis, then it's important that they know what sort of emotions we're expressing. While some already use computer vision systems to do so, Korean scientists have developed what they say is a simpler and more precise technology – users just have to be willing to stick something on their face.

According to the researchers (led by Nae-Eung Lee of Sungkyunkwan University), vision-based emotion-reading systems can be complex and expensive. Additionally, while they work for detecting users' smiles and frowns, they generally aren't able to read things like subtle eye movements.

To that end, the team has developed thin, transparent flexible sensors that are applied to key locations on the user's face. Made up of a layer of carbon nanotubes sandwiched between electrically-conductive elastomer composite films, they're extremely sensitive to mechanical strain brought on by even the most subtle of facial movements.

In tests, they were able to successfully tell if human subjects were laughing or crying, besides being able to determine the direction of their gaze.

Along with their use in robotics, the scientists believe that the low-cost piezoresisitive sensors might also have applications in the field of health care, where they could monitor patients' heartbeats, breathing or other functions.

A paper on the research was recently published in the journal ACS Nano.