Controlled Molecular Assembly for 3D Nanoprinting

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Professor Gang-Yu Liu of the University of California Davis is supported by the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program of the Division of Chemistry to further miniaturize three-dimensional (3D) printing technology from its current minimum feature size of about 0.3 micrometer to less than 0.1 micrometer (100 nanometer), which is a tiny fraction (less than 1/100,000) of the thickness of a human hair. While 3D printing at the macro- and micro-scale is relatively mature, achieving nanometer feature size and precision is still a challenge. To address this, the project tackles two fundamental issues: (a) how to deliver ultra-small amounts of material; and (b) how to deliver the materials to the designed location with nanometer precision. The project advances a new approach with novel chemistry concepts for the assembly of molecules into 3D nanostructures by design. This approach may bring us closer to achieving controlled physical and chemical properties by controlling how the molecules are put together. This project broadens the application of 3D printing in diverse fields, such as in nanotechnology, nanodevices and sensors, tissue engineering, and in biochemistry and biomedical research. It also boosts the capability of additive manufacturing down to the nanometer scale and consequently enhances the competitive edge of the United States 3D printing industry. Graduate students are trained in research methods at the forefront of nanotechnology and additive manufacturing. Professor Liu continues her long-term collaborations with local community colleges and her international education and outreach activities. The outreach activities include summer research opportunities and seminars to stimulate the interest of a diverse group of students in advanced chemistry education and to increase awareness of 3D printing and its societal benefits.The project focuses on controlling the assembly of polymer molecules by direct writing of solutions containing designated components. To achieve molecular level control, a state-of-the-art atomic force microscope is interfaced with a nanofluidic delivery system. The former is an existing technology for high-resolution imaging with nanometer precision, and the latter can be considered as an ultra-small needle (opening as small as 30 nm). The research team has recently improved the delivery of femtoliter droplets, and prior work and preliminary data have demonstrated the feasibility of assembly at the microscale level. The project builds on this foundation. The aim is to reduce the droplet size down to the sub-attoliter level. Towards this end, contact time, pressure and the hydrophobicity of surfaces are modified to weaken inter-molecular and molecule-surface interactions and consequently enhance the kinetics of the assembly process. Long-term collaborations with local community colleges continue with the designed research project, summer research program, seminar and educational activities. These activities attract a more diverse population of students into advanced chemistry education. International research and education activities keep the team well informed and updated in the field of atomic force microscopy and3D printing research and development efforts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.