Mechanical characterization of polydimethylsiloxane (PDMS) exposed to thermal histories up to 300 °C in a vacuum environment

Abstract

Flexible electronic devices consisting of sensors and interconnects integrated with a soft polymer platform are being considered for emerging applications such as smart clothing, soft robotics, conformal batteries, and biomonitoring decals. Fabrication processes for such devices can require that the polymer platform be subjected to temperatures up to 300 °C without a significant deterioration of its physical properties such as stretchability and stiffness. In this communication, we report the stress–strain behavior of relatively thin sheets of polydimethylsiloxane (PDMS) polymer (thickness ∼30 µm) made with a base-to-hardener ratio of 20:1 and heated up to 300 °C in a vacuum environment. It is shown that in spite of the exposure to high temperatures used in this study, the PDMS sheets maintained their hyperelastic behavior as represented by the Ogden model. The elastic modulus is shown to decrease from 0.81 MPa to 0.62 MPa while average strain to failure is shown to decrease from 250% to 106% as the temperature of thermal exposure in vacuum is increased from 100 °C to 300 °C. The retention of high stretchability even after the thermal exposures opens up the possibility of high-density microelectronic circuit interconnects to be fabricated on PDMS substrates.