The innovation engine for new materials

Kai Nambu

Kai Nambu


Mechanical Engineering


University of California, Santa Barbara


Keith Johnson
Brandon Montano

Faculty Sponsor(s): 

Matthew Begley

Faculty Sponsor's Department(s): 

Mechanical Engineering

Project Title: 

Acoustic Focusing of Carbon Fibers in 2D

Project Description: 

Acoustic focusing is using sound waves to move particles. Sound waves create forces that can be used to manipulate fiber position in a fluid. This can be used to create composite materials with conductive properties at low particle density. Low particle density allows conductivity to be achieved while maintaining other properties such as flexibility. This project looked at optimizing fiber patterning in 2D sound fields. To predict patterning, both force and energy models were created. This allows for visualization of forces and torques, and predictive models of patterns based on energy. Fibers will first fill up the lowest energy areas in the field. To create patterns experimentally, piezoelectric buzzers were placed on the walls of a square chamber. Frequencies were set to create standing waves, creating a 2D sound field. Inside the chamber, fibers are placed in liquid where the acoustic forces cause the fibers to move to specific orientations. As fiber length increases, fibers can span multiple high and low energy areas. To avoid rotating through high energy areas, these long fibers can settle in a variety of positions depending on their initial orientation. Fairly continuous patterning was found when the fibers approached the size of the node spacing of the energy fields. This demonstrates feasibility for 2D focusing with fibers. With improvements in chamber design, this has the potential to scale up to create functional materials with conductive properties.