3D printed lenses can turn iPhones into microscopes

Developed by a team at Northwestern University, the customised optical component is 5mm in height and 5mm in diameter and can be 3D printed in about four hours.

“Up until now, we relied heavily on the time-consuming and costly process of polishing lenses,” said Cheng Sun, who worked on the project. “With 3D printing, now you have the freedom to design and customise a lens quickly.”

The customised lens was attached to an iPhone 6s and was able to take high-quality detailed images of a sunset, a moth’s wing and a spot on a weevil’s elyta.

Like all 3D printing, creating these lenses involves placing layer upon layer of material.

Sun likened building the lens to running a film projector. “Instead of projecting one frame, one image after another, we layer one frame on top of another,” Sun said. “It is like playing a movie in a vertical fashion.”

But when researchers first printed the lens, its curved layers, made of a photo-curable resin, created a visible stepping.

“We realised that the layers on top of each other created surface roughness. The layer thickness is typically 5 microns, while the wavelength of visible light is around 0.5 micron. This creates an optically rough surface,” he said. “That was the bottleneck. The roughness made the lens incapable of clear optics.”

To solve that challenge, Sun’s group developed a two-step process of layering and polishing.

“First, we used grayscale images to create more transitions between steps,” Sun said. “Then, we coated the surface with the same photo-curable resin. That then forms the meniscus that further smooths the surface.”

This technique resulted in a transparent lens with a smooth surface.

“I must have tried more than 100 times to get this just right,” said Xiangfan Chen, lead author on the study.

This lens is not the first high-quality lens created by 3D printing. German-based company Nanoscribe has developed a high-precision femto-second 3D printer with 150 nanometer precision, but it builds the lens in a point-by-point fashion instead of layering, Sun said.

“It is a time-consuming process. That is their limitation,” he added. “We wanted to make something comparable but faster and with better quality.

“If you want to make a lens, do you want to make it in two hours or two weeks?” Chen said. “We are very excited about this lens.”

This process could lead to a plethora of new devices with a wide variety of applications in optics and biomedical imaging, Sun said.

Next, the group will experiment in making larger lenses as well as investigating how to integrate the 3D-printed lens with medical devices, such as an endoscope or optical microscope, which could be used to help detect some genetic diseases or cancer.

Earlier this month researchers demonstrated a camera lens that allows photographers to benefit from the advantages of 3D technology using their existing equipment.