A team of researchers have created a highly stretchable touchpad that can be used to write words and play electronic games. This development could pave the way for flexible, wearable devices with numerous applications.
A number of conductors - including metal nanowires and carbon nanotubes - have been used to attempt to make stretchy touchpads, but they are all based on hard materials.
To solve this problem, Chong-Chan Kim and collaborators built a touchpad using hydrogel, a network of hydrophilic polymers that are very stretchable and soft.
A polyacrylamide hydrogel containing lithium chloride salts was used. This acted as a conductor and helped preserve water in the hydrogel. Electrodes found on the ends of the hydrogel panel apply similar voltages, which forms a consistent electrostatic field throughout the system.
The circuit within the hydrogel closes when a finger touches the panel, enabling current to flow from the ends of the strip to the touch point. The team created a controller board to enable communication between a computer and the unique touch panel. Current capturing meters placed at each corner of the strip detect the electrical signals.
A stick figure was drawn using the touchpad, with the data transmitted onto a computer screen. The researchers could write words and play games and the piano with the thin touchpad placed on their arms.
The touchpad was able to function even when it was stretched to over 1000% of its normal area. Subsequent to 100 cycles, the resistance was observed to increase a little, which could be due to water evaporation in the gel, suggested the team.
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