Current innovations in roller embossing—a comprehensive review

Hot embossing (HE) is a micro-manufacturing technique used to develop micro and nano-scaled patterns over a polymer workpiece. The traditional-HE process is only partially implemented in micro-manufacturing industries owing to limitations like low productivity due to batch-wise manufacturing and high processing time. But presently, the demand for large-area patterned polymer substrate is rising due to its applications in diverse areas like displays, micro-lenses, anti-reflection films, micro-fluidic devices, self-cleaning surfaces, etc. Therefore, the traditional hot embossing (HE) process has been modified to the roller hot embossing (RHE) process to meet the increased demand. The RHE process is categorized into the roll-to-plate (R2P) and roll-to-roll (R2R) process. The present paper comprehensively reviews the different advancements in setups of the roll-to-plate (R2P) and roll-to-roll (R2R) hot embossing for large-scale fabrication of micro and nano-sized patterns over the polymer substrate. The graphical, numerical and statistical analysis shows that majorly ultraviolet (UV) lithography/X-ray lithography/electron beam lithography followed by Ni-electroplating/reactive ion etching/wet etching are the most commonly utilized techniques for mold manufacturing. But due to its complexity, researchers have slowly moved towards non-conventional machining processes for mold fabrication i.e., micro-EDM, micro-milling etc. According to a graph showing the percentage distribution of work associated with recent advancements in roller hot embossing, the thermal assisted R2R-HE is the most popular, followed by UV aided R2R-HE, and inductive aided R2R-HE, respectively. The thermal assisted R2R-HE contributes 36% of total innovations in RHE followed by UV aided R2R-HE (14%), and inductive aided R2R-HE (10%).