Mechanics of rollable and foldable film-on-foil electronics

TLDR

The paper presents the mechanics of film‑on‑foil devices, focusing on thin‑film transistors on steel and plastic foils. Thin‑film transistors on thin steel or plastic foils maintain performance when rolled to small radii, with lower‑modulus substrates and neutral‑surface encapsulation enabling even tighter bends, while failure occurs when externally applied and thermally induced strains combine.

Abstract

The mechanics of film-on-foil devices is presented in the context of thin-film transistors on steel and plastic foils. Provided the substrates are thin, such transistors function well after the foils are rolled to small radii of curvature. When a substrate with a lower elastic modulus is used, smaller radii of curvature can be achieved. Furthermore, when the transistors are placed in the neutral surface by sandwiching between a substrate and an encapsulation layer, even smaller radii of curvature can be attained. Transistor failure clearly shows when externally forced and thermally induced strains add to, or subtract from, each other.