In addition to wires, the researchers used chemicals to carve out circular indentations in which the LEDs would be placed. Parviz notes that one challenge in building working electronics and opto-electronics into plastic is that these devices must be made with high heat that would melt the plastic. To get around this problem, his team fabricated LEDs on a separate substrate, ensuring that the devices could easily be removed and transferred onto the plastic lens.
Next, the researchers coated the fully assembled electronic lenses with polymethyl methacrylate (PMMA), a biocompatible material. PMMA is also used to coat hard contact lenses, says Parviz, making his lenses more similar to hard contacts than the soft contacts worn by most people today. In the final step, the researchers molded the plastic into the shape of a lens.
When the team tested the lenses, the circuit was viable and the LEDs lit up. The researchers also placed the lens in a rabbit’s eye for 20 minutes and found no adverse effects. However, they did not turn on the electronics while the lens was in the rabbit’s eye. “I think we have to be careful about what happens to the eye when it turns on,” says Parviz. “It’s a functioning circuit. It could generate some heat. We need to take all the possible precautions to make sure this is safe.” While it’s true that the human body can withstand a range of temperatures, ultimately the circuits must be designed to consume ultralow amounts of power.
“The idea of building a circuit into a contact lens is interesting–it catches the attention,” says George Whitesides, a professor of chemistry at Harvard who is not affiliated with the project. “It has been something that others have certainly talked about, but I, at least, have never seen any kind of implementation.” Whitesides adds that this is an early step, and there is still the issue of providing power to the lens while it is in the eye. In addition, the University of Washington prototype does not have a clear function.
One of the next steps for the team will be to increase the number of LEDs on the lens to a couple hundred, in the hope of making a viable display. Right now, the LEDs are about 300 micrometers in diameter, which obviously limits the number of them that can be put on a lens. In addition, LEDs this size tend to break in the lens-shaping process. Parviz’s team will try to shrink the LEDs to 30 micrometers in future experiments, which could enable the lens to display a few hundred pixels, he says.