Multi-Material and Multi-Functional 3D Printing: External Field Assisted Stereolithography

By combining various materials that serve mechanical, electrical, and thermal functions with controlled local distributions, smart devices and machines with multiple functionalities can be fabricated. The traditional manufacturing processes such as machining and molding limit the full functionality of particle–polymer composites owing to the lack of control on particle distribution. Multi-material additive manufacturing technology allows a higher degree of design by controlling orientations/alignments and local compositions of particles in the polymer matrix. In this work, the multi-material and multi-functional 3D printing process, external field assisted stereolithography, is developed and investigated. First, an additive manufacturing process, named Magnetic Field-assisted Projection Stereolithography (M-PSL), is presented for 3D printing of smart polymer composites. The magnetic alignment, curing mechanisms, and manufacturing process planning are discussed. Test cases have been successfully fabricated for remote control under external magnetic fields, showing the capability of printed smart polymer composites on performing desired functions. The printed magnetic field-responsive smart polymer composite creates a wide range of motions, opening up possibilities for various new applications, like sensing and actuation in soft robotics, biomedical devices, and autonomous systems. Besides magnetic alignment, this work reports another new particle patterning approach during additive manufacturing to fabricate multi-functional smart composite objects. An acoustic field is integrated into the projection based stereolithography system to pattern different micro- and nano- particles into dense parallel curves or networks in the liquid resin. Effects of acoustic field settings and manufacturing process parameters on patterning are modeled and experimentally characterized. Various particle patterning results are presented. The feasibility of the Acoustic-field-assisted Projection Stereolithography (A-PSL) process for multi-functional particle-polymer composite fabrication has been verified. In order to design and fabricate functional polymer composites with desired properties and functions, the correlation between micro-scale material distribution and macroscopic composite performance is investigated. Micro-scale particle distribution parameters, including particle loading fraction, particle assembly, microstructure orientation, and particle distribution patterns, are investigated. Magnetic functions, thermal functions and mechanical functions are tested. Test cases of remote control devices and thermal management application are demonstrated to verify the enhanced material properties and functionality of the printed polymer composites.