Facile and cost-effective PDMS double-casting method based on curing temperature and ratio for solvent detecting applications

Abstract

This study proposes a polydimethylsiloxane (PDMS) double-casting method based on curing ratio and temperature. The master mold is fabricated by first curing with high-temperature, high curing agent ratio of PDMS, followed by secondary curing with low-temperature, low-ratio PDMS to create a replica mold. The distribution of the Si–H stretch bonding and the CH3 symmetric and asymmetric stretching are altered when the curing temperature and curing ratio sequence is changed. The difference in the distribution of chemical bonds at the interface between the two molds results in double casting. Moreover, the roughness and water contact angle are measured to determine the changes in the surface properties of the master and replica molds after double casting. The double-casting method maintains the hydrophobicity of both the master and replica molds without altering the properties of PDMS. Furthermore, the one-dimensional pattern formed by the interlayer structure of the fused deposition modeling-type three-dimensional (3D) printing mold is successfully double cast. Finally, the chemical sensor for detecting the type of solvent was fabricated using the double-casting method and experimentally demonstrated. This study demonstrates a facile, simple, and cost-effective PDMS double-casting method for 3D-printed mold replicas.