Artificial sight

Artificial sight with solar cells

Monday 03 Jul 17


Rasmus Schmidt Davidsen
DTU Nanolab
+4526 18 72 49
Rasmus Schmidt Davidsen is postdoc at DTU Nanotech and a successful researcher within optimisation of solar cells. Now he wants to help the blind see by using microscopic solar cells.

Worldwide more than two million people are unable to see because the photoreceptors in their eyes do not work properly. A photoreceptor is a specific type of cell which works by absorbing the light and sending electrical impulses to the brain. A person is blind if his or her brain does not receive these impulses. This is the situation Rasmus Schmidt Davidsen hopes to change by developing artificial sight.

“We are developing an implant with thousands of small isolated solar cells which can be operated into the eye behind the retina of blind patients”, Rasmus Schmidt Davidsen says.

Rasmus Schmidt Davidsen explains how it is possible: “Photoreceptors in the eye actually behave like solar cells, and when we realised this fact we came up with the idea that we could use some of my research in the area of solar cells to develop a chip for blind patients. Each solar cell will correspond to a pixel in the artificial sight we are trying to create. Of course we will attempt to maximise the number of pixels, to make the eyesight as good as possible”.

Big challenge to work with small things
“Getting enough electricity from natural light is one of the biggest challenges”, says Rasmus Schmidt Davidsen. “Even with the best solar cells, it is not possible for us to create a solar cell that generates enough electricity from visible light, when we also need thousands of isolated cells on a limited area: We are limited to a solar cell area of 3 x 3 mm, if surgeons are to be able to operate the chip into the eye. And we cannot even use the entire area because there has to be room for electrodes and holes in the chip in order for the tissue fluids to flow freely in the eye.”

Thankfully, other research groups have solved the problem with the lack of light. The source of light may be placed e.g. in a pair of glasses such as e.g. Google glass.

“With these types of glasses we are able to send light in a fitting frequency, which hits the retina where we place our chip – therefore we are not overly worried about that aspect”, says Rasmus Schmidt Davidsen.

Artificial sight
The 40 micrometer high polymer columns on the solar cell are electrically active and have contact with the underlying solar cell implant so that they can direct the flow from here to the nerve cells of the eye tissue. Over time, the nerve cells grow into the valleys between the columns.

Medical backing
There are, however, biological challenges of which the young postdoc has only recently been made aware. Therefore, Rasmus Schmidt Davidsen is very content that he is collaborating with Toke Bek, leading chief surgeon and clinical professor at the eye ward at Aarhus University Hospital. At Aarhus University Hospital, the medical expertise is present as well as a special agreement with a large Danish company.

“We are conducting a lot of research and have a good collaboration with Danish Crown who delivers fresh tissue from pigs, “says Toke Bek. “We receive fresh eye tissue within an hour. We order it the day before and receive 30-35 cooled pigs’ eyes each morning”.

The fresh pigs’ eyes give Toke Bek and Rasmus Schmidt Davidsen a unique opportunity to test the solar cell implants on living tissue similar to the ultimate target of the project, namely human eyes.

It will take a long time before it is actually possible to insert the implants in human eyes. The implant will not give the patient normal eyesight, but to a blind person it will make a big difference.

Profitable collaboration
“At the moment, we are working on the first prototype of the implant. In the time to come, it will become apparent whether a reaction in the nerve cells of the pigs’ eyes may be produced. We need to place it as closely as one would do in an operation, but it is a very small piece of tissue, cut out with a scalpel, add to that our little chip – we’re talking about 3 x 3 mm – and then we have to put some light on it and see whether it produces any electricity.”

Chief surgeon Toke Bek is hopeful for the project but sees many challenges. “One of them is the bio complexity. There is a very great likelihood that the tissue will reject the foreign objects. Especially in the eye. But the nano people may be able to encapsulate the implant in materials which the tissue will not reject. And they are able to make things very very small. Finally, the optical efficiency of the solar cells will be great as they use almost 100 % of the light. This is also encouraging for the continuation of the project. There are some good technological advantages in collaboration with DTU.”

Solar cells implanted in the eye's retina can replace a small part of the photoreceptors that do not work.