We've seen robots that can respond to touch, to visual cues and of course voice commands, but what about a robot with a sense of taste? Scientists have developed an experimental device built to explore this possibility, and in its current form can already conduct a little taste test to see if its bathwater has been contaminated.

Scientists at the University of California, Davis and Carnegie Mellon University (CMU) sought to replicate our sense of taste with what they call a biosensing module fitted to robotic gripping arm. Within this module is E. coli bacteria that had been engineered specifically to react to a chemical known as IPTG.

The modified bacterial cells are encircled by a porous membrane that keeps them contained but allows chemicals like IPTG to make their way inside. When that happens, the cells respond by producing a fluorescent protein.

The robotic gripper with this biosensing module attached is then able to interpret this light as a control signal, which in this case was used to determine whether it should pick something up and place it in a bath of water or not. After spending hours resting in the water first to check for IPTG, the robotic arm was able to then declare it safe and plonk a big yellow ball into the bath.

While slow-working and rudimentary, the team considers its taste-testing machine a proof-of-concept for new kinds of soft robots inspired by biology. The challenges ahead include building robots that can "taste" more than one thing and ones that can detect different concentrations. But the upside is robots with very unique potential that can adapt and respond to their surroundings.

"By combining our work in flexible electronics and robotic skin with synthetic biology, we are closer to future breakthroughs like soft biohybrid robots that can adapt their abilities to sense, feel and move in response to changes in their environmental conditions," says Carmel Majidi, a co-author of the study and associate professor of mechanical engineering at CMU.

The research was published in the journal Science Robotics, and the video below shows the robot in action.