Light receptors have been 3D printed on a hemispherical surface for the first time, an advance that could eventually lead to so-called bionic eyes that restore sight.

bionic eyes
Researchers have 3D printed an image sensing array on a hemisphere, a first-of-its-kind prototype for a "bionic eye" (credit: University of Minnesota, McAlpine Group)

Researchers from the University of Minnesota started with a hemispherical glass dome to show how they could overcome the challenge of printing electronics on a curved surface.

Using a custom-built 3D printer, they started with a base ink of silver particles. The dispensed ink remained in place and dried uniformly instead of running down the curved surface. The researchers then used semiconducting polymer materials to print photodiodes, which convert light into electricity. The entire process - seen below - is said to take about an hour.

"Bionic eyes are usually thought of as science fiction, but now we are closer than ever using a multimaterial 3D printer," said Michael McAlpine, a co-author of the study published in Advanced Materials, and University of Minnesota Benjamin Mayhugh Associate Professor of Mechanical Engineering.

McAlpine said the most surprising part of the process was the 25 per cent efficiency in converting the light into electricity they achieved with the fully 3D printed semiconductors.

"We have a long way to go to routinely print active electronics reliably, but our 3D printed semiconductors are now starting to show that they could potentially rival the efficiency of semiconducting devices fabricated in microfabrication facilities," McAlpine said. "Plus, we can easily print a semiconducting device on a curved surface, and they can't."

According to McAlpine, the next steps are to create a prototype with additional light receptors that are more efficient. They will investigate also a way to print on a soft hemispherical material that can be implanted into a real eye.

McAlpine and his team are active in the integration of 3D printing, electronics, and biology on a single platform. To date, they have 3D printed a bionic ear, life-like artificial organs for surgical practice, electronic fabric that could serve as so-called "bionic skin", electronics directly on a moving hand, and cells and scaffolds that could help people living with spinal cord injuries regain some function.

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