Manufacturing bioinspired flexible materials using ultrasound directed self-assembly and 3D printing

Biological materials that are composed of hierarchical microstructures embedded in a matrix material can display enhanced mechanical or material properties compared to an unstructured mixture of the same constituent materials. In this work, ultrasound directed self-assembly was integrated with 3D printing (direct-write (DW)) in a new manufacturing process called “ultrasound DW”, to enable the fabrication of engineered materials with properties mimicking those of natural materials. This process allows 3D printing feedstock that consists of a liquid photopolymer resin with dispersed microfibers, and enables fabricating materials with lines of aligned carbon microfibers. The effect of the ultrasound operating frequency and print speed on the alignment of the fibers, distance between adjacent lines of aligned fibers, as well as the resulting electrical conductivity and mechanical properties of the samples were evaluated. The results showed that the lines of aligned fibers in the material samples display statistically significant differences in terms of the distance between the adjacent lines of aligned fibers when looking at the factors of the ultrasound operating frequency and the print speed. The lines of aligned fibers form local percolated networks resulting in electrically conductive areas. The ultrasound DW process allows the fabrication of materials with integrated substructures that tune specific material properties.