Using a new technique that can create vacancies at any site across a material and then shrink it to about 1/2,000 of its original volume, MIT researchers have designed nanotechnology devices that could be used for optical computing and other applications involving the manipulation of visible light. The new fabrication technique, known as "implosion carving," allows researchers to imprint features throughout a hydrogel using photopatterning. If patterned with a resolution of about 800 nanometers, these features can then be shrunk to less than 100 nanometers. Because that resolution is smaller than the wavelength of light, the devices can bend light in specific ways that allow them to perform optical computations. Quansan Yang, a former MIT postdoc, now an assistant professor at the University of Washington, states, "In order to enable nanophotonic applications in visible light, we need to make nanostructures with feature sizes with a resolution less than 100 nanometers. Only in that way can we precisely create the structure that can manipulate visible light." The researchers demonstrated a photonic device that can perform a simple digit-classification task, but future versions could be used for high-speed imaging and information processing. The researchers also created several 3D shapes, including a helix and a structure inspired by a butterfly wing. Some of these structures are too thin, and have too high an aspect ratio, to be stably created using conventional two-photon lithography. They also created a device that could perform a simple calculation known as digit classification, a task that is traditionally used to test the performance of neural networks. During this task, the device was presented with a digit, such as 1 or 5, and had to light up a specific location to indicate which number was detected. The pattern of vacancies would diffract input light as it passed through many layers of patterned hydrogel, determining the output light based on the shape of the digit entered into the system. "This is a purely optical system that effectively performs optical computing," So says. The researchers now plan to use the same principles to build optical devices that could classify cells based on their state as they flow through a microfluidic device. This could help identify rare cells such as circulating tumor cells in a blood sample. This approach could also enable the creation of high-throughput imaging techniques for applications such as analyzing tissue samples from biopsies or surgical specimens. If adapted to work with other materials such as hydrophobic polymers, it could also be used to create channels within 3D nanofluidic devices. The research was funded in part by the MIT-Fujikura Partnership Fund, the U.S. Army Research Office, and the Howard Hughes Medical Institute.
Blogger's Review: The breakthrough of this technology lies not only in achieving nanoscale photonic device fabrication but also in providing new possibilities for future optical computing. By integrating deep learning algorithms, researchers can identify optimal designs among millions of parameters, showcasing the immense potential of interdisciplinary research. Future applications may revolutionize not just computing but also bring transformative changes in the medical field.