Seoul: Researchers have developed a wearable touch screen panel that is highly stretchable and can be used to write words and play electronic games. The thin flexible ionic touchpad that is highly transparent, can be placed on one's arm to play video games, draw, write words as well as to play the piano, the study said. The touchpad is made of hydrogel, a network of hydrophilic polymers that are soft and very stretchable, unlike the hard materials such as carbon nanotubes and metal nanowires earlier explored for the stretchy touchpads. Moreover, the touchpad was still able to operate when it was stretched to more than 1,000 per cent of its normal area. However, the resistance was found to increase slightly after 100 cycles, which may be due to water evaporation in the gel, said Chong-Chan Kim from the Seoul National University in South Korea, in a paper published in the journal Science. For the stretchy touchpad, the team used a polyacrylamide hydrogel containing lithium chloride salts, which act as conductor and help retain water in the hydrogel. Electrodes on the ends of the hydrogel panel apply similar voltages, which creates a uniform electrostatic field across the system. When a finger touches the panel, it closes the circuit within the hydrogel, allowing current to flow from both ends of the strip to the touch point. At each corner of the strip, meters that capture current detect the electrical signals. Because human-computer interactions are increasingly important, touch panels may require stretchability and biocompatibility in order to allow integration with the human body, the researchers said. The team also developed a controller board to facilitate communication between the ionic touch panel and a computer.