Mechanical Properties of Graded Polydimethylsiloxane for Flexible Electronics

The extensive use of polydimethysiloxane (PDMS) in the context of flexible systems such as flexible display has up grown an issue of its flexibility upon high loadings and rupture. In previous study, PDMS substrates failed through the rupture and delaminated completely at 120% at global strain. Graded PDMS samples consisting five different layers of mixing ratios was designed to effectively fulfill the mechanical function. Each layer was differ in color to accentuate the difference of mixing ratios. The first layer had the mixing ratio of base polymer to curing agent 2:1, followed by 5:1, 10:1, 15:1 and 20:1 respectively. The graded PDMS samples were prepared using a simple casting, curing, stacking and cutting process. . This study presents the measurement of the mechanical properties of Graded PDMS based on the mixing ratio of base polymer to curing agent. A tensile test and fracture test were performed with a Universal Testing Machine at room temperature. The new finding is that when the graded PDMS were stacked together varying the layers from hardest (2:1) to softest (20:1) PDMS substrates, the range of flexibility is very wide. It can be seen from the stress-strain curves that the graded PDMS sample showed flexibility and yet can elongate up 170% strain before failing. It could be concluded that by designing and improving the graded PDMS combining the hardest (2:1) to the softest (20:1) PDMS substrates can vary its mechanical properties to approach the hardest biological materials such as bone and tooth enamel, whereas still can be reversibly stretchable up to 170% strain without failure. This study will be of use to all the technological communities who are in used of PDMS polymers for their specific investigations and applications in flexible system. (paper)