Bubble-free replication of large area microstructures using gas-assisted UV embossing with modified reversal imprinting and gap-retained vacuuming

Abstract

Air bubble defects have been regarded as a critical problem in ultraviolet (UV)-based imprinting/embossing processes, especially in large area fabrication. This paper reports a gas-assisted UV embossing process for bubble-free replication of large area microstructures. This gas-assisted pressurizing process provides uniform embossing pressure over the whole large area, while UV curing enables the process to be performed at room temperature and low pressure. To overcome the problem of air bubble entrapments in the large area UV embossing process, the mechanisms of modified reversal imprinting and gap-retained vacuuming have been developed and used. Experimental results show that the microstructures have been successfully transferred from the stamper to the polymethylmethacrylate substrate with the size of 230 × 203 mm2 inducing no air bubble defects.