Ultrasound directed self-assembly of non-periodic patterns of particles

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This award supports research into the theoretical and experimental foundation required to organize and orient particles dispersed in a fluid medium into specific patterns, using the forces associated with an ultrasound wave field. The research specifically focuses on using multi-frequency rather than single-frequency ultrasound wave fields to enable assembling arbitrary, non-periodic patterns of particles. A host of engineering applications could benefit from this research, including particle and cell separation processes, mixing and dispersion control of suspensions, non-contact particle manipulation, and manufacturing of engineered composite materials with tailored properties. Fundamental theory to optimize the parameters (amplitude, phase, and set of frequencies) to assemble any pattern of spherical particles in multiple dimensions will be developed. Broadening participation of underrepresented groups in STEM education will be promoted by partnering with the Center for Enhancement of Engineering Diversity at Virginia Tech and contributing to the Computers and Technology summer camp and the Women’s Preview Weekend.The research objective of this award is to theoretically derive and experimentally validate the scientific foundation that enables organizing and orienting particles dispersed in a fluid medium into any periodic or non-periodic pattern, utilizing the forces associated with a multi-frequency ultrasound wave field. A theoretical and experimental study will be implemented that covers four technical thrusts to solve this problem. They include: 1) derivation of multi-frequency ultrasound directed self-assembly (DSA) theory for both spherical and high aspect ratio particles, 2) experimental validation of the multi-frequency ultrasound DSA theory, 3) integration of multi-frequency ultrasound DSA with vat-polymerization AM to demonstrate proof-of-concept of manufacturing polymer matrix composite materials with tailored properties, and 4) packaging the knowledge resulting from this research in an open-source software tool to make it accessible for other users. Together, the outcomes of these four research thrusts will describe the physical underpinnings of ultrasound DSA based on multi-frequency wave fields. The results of this award will advance discovery, implementation, and deployment of external field DSA methods, and control of organization and orientation of particulates within multiphase mixtures.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.