Engineers Invent Single Lens for 3-D Microscopic Imaging
By Pam Frost Gorder
Other 3-D microscopes use multiple lenses or cameras that move around an object; the new lens is the first single, stationary lens to create microscopic 3-D images by itself.
Allen Yi, associate professor of integrated systems engineering, calls the lens a proof of concept for microelectronics and medical device manufacturers, who currently use very complex machinery to view the tiny components they assemble.
“Ultimately, we hope to help manufacturers reduce the number and sizes of equipment pieces they need to miniaturize products,” Yi adds.
Yi and postdoctoral researcher Lei Li milled the prototype lens, which is about the size of a fingernail and looks like a gem, with a flat top surrounded by eight facets. But while gemstones are cut for symmetry, this lens is not symmetric. The sizes and angles of the facets vary in minute ways that are hard to see with the naked eye. Such a lens is called a “freeform lens.”
Li, of the college’s Center for Affordable Nanoengineering of Polymeric Biomedical Devices, a National Science Foundation Nanoscale Science and Engineering Center, wrote a computer program to design a freeform lens capable of imaging microscopic objects.
Then Yi and Li used a commercially available ultraprecision machine with a diamond tool to cut the shape from a piece of the common thermoplastic material polymethyl methacrylate, a transparent plastic sometimes called acrylic.
The precision machine shaved bits of plastic from the lens in increments as small as 10 nanometers, or 10 billionths of a meter. The final lens resembled a rhinestone, with a faceted top and a wide, flat bottom.
Each facet captured an image of the objects from a different angle, which can be combined on a computer into a 3-D image.
“For us, the most attractive part of this project is we will be able to see the real shape of micro-samples instead of just a two-dimensional projection,” says Li.
In the future, Yi would like to develop the technology for manufacturers. He points to the medical testing industry, which is working to shrink devices that analyze fluid samples. Cutting tiny reservoirs and channels in plastic requires a clear view, and the depths must be carved with precision. Other devices also could benefit from similar tiny lenses. The researchers have since produced a grid-shaped array of lenses made to fit an optical imager for wide-angle sensing.
