A Review on United States Patents to Prevent Mechanical Failures in Foldable Smartphones

Abstract A foldable smartphone is an exciting new approach for future mobile systems. With some early models being introduced to the market, research and development is being performed to increase the reliability of future systems. Mechanical failure of the display is the major source of foldable smartphone's reliability issues. The display is a laminate structure including an organic light emitting diode (OLED) layer (emission layer and pixel electrode layer), a touch panel, a polarizer, and multiple protective layers in addition to multiple functional coatings and supporting structures. The display is exposed to repeated folding, finger touch, and the impact of external sharp objects. In addition, mechanical behavior changes through the thickness of the display; which adds extra challenges in preventing damage to vital components of the display. This review covers more than 100 U.S. patents about the mechanical failures in foldable smartphones published or filed after 2015. Different inventions reviewed are to design a foldable configuration to prevent mechanical failures resulting from the following four mechanisms: (1) plastic deformation (yielding, creep, and fatigue); (2) fracture; (3) delamination; and (4) buckling (warping, buckling, wrinkling, and creasing).