ENME Webcast Archives

LEADERS IN MECHANICAL ENGINEERING LECTURE SERIES - SPRING 2007

Mechanics of Flexible Macroelectronics

Lecturer: Teng Li - Mechanical Engineering Department, University of Maryland

Original Air Date: Friday, April 27th at 2:00pm

Abstract: The advent of flat-panel displays has opened the era of macroelectronics. Enormous interests are gathering in recent years towards the nascent technology of flexible macroelectronics. The vast applications, e.g., paper-like displays, printable solar cells, electronic skins, and sensitive textiles, will impact everyone's daily life. Future success of this promising technology largely relies on the reduced cost and enhanced portability of the flexible electronic devices, attributes that will come from new choice of materials and of manufacturing processes. For example, electronic materials (metals, dielectrics and semiconductors) can be patterned into micro/nano structures on soft substrates, through a roll-to-roll fabrication, resulting in lightweight, rugged, and flexible devices. These devices will have diverse architectures, hybrid materials, and small features. The mechanical behavior of these large scale structures with micro/nano scale features poses significant challenges to the creation of the new technologies. For example, thin films of most electronic materials fracture at small strains (less than ~1%). How to use these materials to make electronic devices with reliable deformability under cyclic loading remains uncertain. This talk describes the ongoing work in the emerging field of research ? mechanics of flexible macroelectronics. Particular focus is placed on how to make nanoscale thin films of various electronic materials mechanically deformable and electronically functional when the whole device is subject to large, cyclic stretching, bending or twisting, a key challenge confronted by this nascent technology. We first focus on understanding the tensile behavior of thin metal films on polymer substrates, gaining insight into the rupture mechanisms of such a representative architecture in flexible macroelectronics. We then identify and quantify the physical parameters governing the film rupture strains, shedding light on the materials optimization to achieve better device deformability. Next we broaden the focus onto general electronic materials and explore possible ways to enhance their deformability on polymer substrates. We identify the mechanisms of large, reversible deformability of thin metal films on elastomeric substrates, and then propose a general principle of making thin films of stiff materials deformable by suitably patterning. Such patterned films can serve as general platforms for flexible macroelectronics.