Three Dimensional Nanolithography via Combined Scanning Near-Field Optical Microscopy and Photopolymerization

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Gang-Yu Liu at the University of California-Davis is supported in an award from the Macromolecular, Supramolecular and Nanochemistry (MSN) Program that aims at developing advanced chemistry methodologies for three-dimensional (3D) printing with nanometer precision. 3D printers enable production of objects by custom-design. Cutting-edge 3D fabrication technology has reached high spatial accuracy, down to 0.3 micrometers. This project aims at further miniaturizing the technology down to genuine nanometer scale, 100 nm, in all three dimensions (1/800-1/100,000 of human hair). This will be achieved by a very small light source using near-field scanning optical microscopy technology that directs a chemical reaction, such as polymerization on a surface, layer-by-layer, following the scanning trajectory of the probe, and as such producing 3D nanostructures by design. The work extends current 3D capability into the nanometer region. The materials produced by 3D nanoprinting provide new opportunities in various fields including optical and electronic devices, catalysis, and biosensor and biodevices where the local environment of active ingredients dictate the subsequent processes and device performance. Liu and her team plan to continue their outreach effort in working with high school students via UC Davis programs such as the ACS Project SEED program and Young Scholars Program, and with the general public via the Davis Science Center, Nanoexplore program.The project takes advantage of the Liu's molecular resolution nanofabrication and imaging technology in 2D, high intensity apertureless near field scanning optical microscopy (NSOM), and surface chemistry. Using NSOM to activate a photosensitizer and produce radicals locally, photoinduced thiol-ene click chemistry will be utilized layer-by-layer, following the designed geometry to yield the designed 3D structures. Unlike currently used 3D printers that enable microlithography, this research takes advantage of NSOM's spatial precision and extends 3D fabrication to the nanometer region. The goal is to achieve the highest spatial precision and resolution in 3D nanolithography. Student training includes: (a) precision mechanic movement and feature tracking; (b) high resolution imaging and structure characterization using scanning probe microscopy technology including AFM and apertureless NSOM, (c) advanced skills in computer programing and 3D printing; (d) surface chemistry at nanoenvironment including absorption, pattern transfer, and desorption, and (e) photopolymerization chemistry with high spatial resolution.