Touchscreens have transformed the way we interact with electronics, enabling the development of elegant handheld devices. But currently, their screens are limited to a fixed size. As flexible and wearable electronics are in development, the touchscreens we’ll need in the future will have to be both flexible and biocompatible. In an investigation recently published in Science, researchers have designed an ionic touchscreen that boasts stretchability and biocompatibility, allowing easy integration with the human body.

The team selected a hydrogel-based material for their work. Hydrogels are soft, water-filled polymer networks; their mechanical properties are similar to those of certain tissues, and they can be made of biocompatible materials. As an added bonus, they’re highly transparent. In this case, the scientists selected an ionic hydrogel—a polyacrylamide base containing lithium chloride salts.

To get the gel to function, it has to conduct electricity, which is why there’s lithium chloride present. To produce a uniform electrostatic field across the panel, voltage was applied at all the panel corners. When a person touches the panel with their finger, the finger acts as a conductor that is grounded. As a result, a potential difference is generated between the electrode and the touch point causing the current to flow from the electrode through the finger.