Collaborative Research: Surfing the order parameter - assembling nanoparticle structures through phase transitions in liquid crystal solvents

Tufts University, Medford MA

Investigators

Abstract

Non-technical Abstract This project is focused on understanding how nanoparticles can be used to form novel structures such as capsules and foams by dispersing them in a liquid crystal. Liquid crystals are ordered fluids commonly used in LCD displays, but this project uses the liquid crystal in an unconventional way - as a solvent for nanoparticles. The novel process the team are investigating offers a rapid, scalable and largely unexploited alternative for particle assembly. They are using a custom particle design, with high-speed microscopy and new computational approaches to tune the interactions between the nanoparticles and the liquid crystal. The work plan focuses on three fundamental scientific questions: 1) How are particles transported by the fluid? 2) How does particle surface treatment control structure formation? And 3) What range of structures are possible and how are they selected? They are testing a range of particle sizes, and process and compositional parameters in a close collaboration of experiment and theory. Gaining fundamental understanding of these novel material systems will be transformative in enabling rational design of multiscale structures from simple components. The process is relevant to a wide range of applications, including encapsulation technologies in medicine, skincare, cosmetics and food science. UCM is a Hispanic Serving Institution and serves a diverse yet educationally disadvantaged part of the state. The project team is committed to mentoring students in STEM at all levels and through this collaboration numerous graduate and undergraduate students are receiving cutting-edge training to enhance their competitiveness in the workforce. Undergraduate research is an integral part of physics programs at research intensive UCM and Tufts and at SCU, a primarily undergraduate institution with a strong tradition of chemistry research. UCM is partnering with the Tufts Visiting and Early Research Scholars Experience program (VERSE) to recruit students from underrepresented groups to begin research early in their careers. Partnerships created by this project are building a strong link between three higher education institutions in both research and education. Technical Abstract This project is focused on understanding physical transport mechanisms for nanoparticles in liquid crystals and specifically how they can be leveraged to sculpt nanoparticle-based structures. The process the team investigate exploits the liquid crystal in an unconventional way, by using this anisotropic fluid as a solvent for nanoparticles and tuning interactions between these two materials. This process offers a rapid, scalable and largely unexploited alternative for particle assembly. The team is investigating this assembly process using custom particle design in a collaboration between The University of California, Merced and Santa Clara University, with high-speed fluorescence microscopy experiments at Merced and new computational approaches performed at Tufts University. The work plan focuses on three inquiry-based specific aims to be performed collaboratively 1) How are particles transported by moving phase boundaries? 2) How does particle surface treatment control structure formation? And 3) What range of structures are possible and how are they selected? This project has the potential to develop a range of novel nanoparticle-based structures, however, as well as illuminating the fundamental mechanisms governing structure selection which are still largely unknown. Gaining fundamental understanding will be transformative in enabling rational design of multiscale structures from simple components. The project has a broad scientific impact on the soft matter community and beyond by providing fundamental insights into a novel process relevant to a wide range of applications in particle transport, aggregation and nanoscience. The team takes advantage of liquid crystal’s ability to spontaneously segregate and organize nanoparticles by their chemical and/or physical properties using well known materials. A key feature of the process is that the structures (and formation mechanisms) depend only on particle size – not composition. This means that any suitably functionalized nanoparticle can be assembled – broadening the project’s impact beyond the specific aims. It should be possible to achieve similar structures in a broad range of chemical environments, opening up encapsulation technologies in medicine, skincare, cosmetics and food science. Simulation codes from this project will impact the scientific soft matter community as a resource for future investigations. These codes will be disseminated as open-source software. 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.