Hierarchical Patterned Films for Large-Area Roll-to-Roll Manufacturing

Hierarchical materials have the potential to be transformational for a variety of applications, providing components which simultaneously offer the best performance attributes of ceramics, metals, and plastics. Hierarchical materials are materials which concurrently realize functional features on multiple length scales (sub-micron up to a millimeter level). This allows large void space in a material structure to be filled with load bearing members, adding compliance to the material without significantly increasing the density. Researchers have pursued hierarchical material structures for almost 20 years, leveraging inspiration from both nature and architecture, but few have shown success in synthetically re-creating these structures at multiple length scales. Prior attempts to experimentally fabricate hierarchical structures using 3D printing have only produced structures at large (mm) scales while micro-fabrication techniques using expensive custom equipment to produce sub-micron structures do not translate well to high-volume, low-cost production. PARC has developed a novel approach for manufacturing large area hierarchical materials based on electrohydrodynamic film patterning (EHD-FP) that mitigates both of the aforementioned shortcomings. EHD-FP enables the rapid fabrication of hierarchical materials with features at multiple length scales while creating a process which scales to fabricate large-area patterned films at low cost. We present our mechanical testing data for two-dimensional (2D) hierarchical kagome and triangular truss structures made with EHD-FP and ultraviolet (UV) curable polymers. Using the EHD-FP process, hierarchical films are easily and rapidly created with low viscosity UV cross-linked polymers. PARCs batch EHD-FP process and conceptualization for a large-area roll-to-roll system for EHD-FP are presented. Our results provide confirmation of some of the underlying mechanics for hierarchical materials, allowing for a path towards transformative, large-area hierarchical materials with superior functionality over bulk constituents.