Bubble-printing of Colloidal Nanoparticles into Functional Materials and Devices

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This grant supports research that contributes new knowledge in printing technology, which is manufacturing with colloidal nanoparticles as building blocks. Printing of colloidal nanoparticles into functional materials and devices provides an economically viable way towards manufacturing nano-scale structures and components for diverse applications such as sensing, energy harvesting, solid-state lighting, and information displays. Such a technological capability advances national prosperity and security. Printing techniques such as gravure printing and inkjet printing have advantages in eliminating tedious mask alignment and multi-step processes required in conventional lithography for device fabrication. However, existing printing techniques have low resolution, considerable post-processing time, and special requirements on the properties of colloidal solutions. Bubble printing exploits optically controlled bubbles to enable versatile patterning of colloidal particles on most substrates. This award supports fundamental research to provide needed knowledge for the development of bubble printing into a viable technology for both prototyping and scalable manufacturing of functional materials and devices. The research is at the interfaces of photonics, fluidics, colloidal science, and manufacturing sciences, provides interdisciplinary research opportunities for students and helps broaden participation of women and underrepresented minority students in manufacturing and engineering. The incorporation of the research results into outreach programs helps promote public interest in nanotechnology and scientific advancement. Bubble printing employs a laser beam to generate a microbubble at the interface of colloidal suspension and a substrate via opto-thermal effects. The bubble captures and immobilizes the colloidal nanoparticles on the substrate through coordinated actions of Marangoni convection, surface tension, gas pressure, and substrate adhesion. Bubble printing can overcome the limitations of existing printing techniques such as poor resolution and feature fidelity. However, some scientific barriers need to be overcome to realize the full potential of bubble printing for scalable fabrication of functional materials and devices from colloidal particles. This research is to fill the knowledge gap on the mechanisms of bubble generation and printing. The research approach is to perform experiments supported by simulations to advance the fundamental understanding of bubble dynamics and nanoparticle assembly, and elucidate the novel physical mechanism for rapid transport, capture and targeted immobilization of colloidal particles at the generation of multiple microbubbles. The project develops a system for scalable printing of functional materials and devices with high resolution, throughput, stability and reproducibility, and demonstrate the capability of bubble printing for site-specific fabrication and integration of multiple functional devices on single platforms.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.