SNAP-Chip: An All-on-a-Chip System for IC-Compatible, Additive Printing in the Deep-Nanometer Regime using Yoctoliter-to-Zeptoliter Scale Droplets

Research supported by this grant focuses on the science of electrified ejection, transport, and vaporization dynamics of nanodroplets, which constitute very small volumes in the yoctoliter-to-zeptoliter (i.e., 10-24 to 10-21 liters) range. The new knowledge gained will be leveraged to yield an all-on-a-chip, integrated circuit compatible nanomanufacturing technique with efficiencies in pattern resolution, operating power, cost, and system complexity. This technique has the potential to find use in diverse industries such as integrated circuits, micro-/nano- electromechanical systems, flexible electronics, touchscreen, industrial spraying, and security printing. The project will train students on interdisciplinary topics such as chip fabrication, materials science, nanotechnology and electrohydrodynamics. Further impacts will be achieved through K-12 centered outreach programs that include emphasis on minority and underrepresented students, organization of a Summer School on Nanomanufacturing, and engagement with the industry as a part of technology transfer initiatives. Overall, the scientific contributions and broader impacts of this project will advance economic prosperity and national security through technology as well as workforce development in nanomanufacturing. The research objective of this project is to test the hypothesis that nanoscopic miniaturization and monolithic, on-chip electrification of nozzles in a nanoelectrohydrodynamic printer will yield a transformative new performance regime of sub-continuum nano-dripping. In this regime, droplets with diameters smaller than 20 nanometers will be extracted using ultra-low electric stresses to additively print three-dimensional, solid-state patterns in the deep-nanometer size regime. While electrohydrodynamic droplet ejection at the micro- and macro-scales arises from a combination of fluid surface tension, electric, viscous and inertial forces, continuum theory does not adequately explain meniscus instability in the deep-nanometer regime where thermal fluctuations at the liquid-air interface and electrokinetic contributions have been predicted to play a significant role. The project's hypothesis will be tested using a synergistic combination of coupled-physics experiments and mesoscale Many-body Dissipative Particle Dynamics simulations involving a Scanning Nanodroplet Additive Printer-on-a-Chip (SNAP-Chip). SNAP-Chip will miniaturize both the nozzle and the nozzle-electrode gap by at least an order of magnitude in comparison to micron-scale geometries of prior art through the fabrication of a droplet generator on a silicon substrate. This miniaturization makes sub-continuum nano-dripping experimentally accessible and will be employed to print features that are sized as low as single-digit nanometers in three-dimensions. 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.