Highly Stretchable and Reliable Metal-Oxide Thin-Film-Transistors and Integrated Circuits on a Molecular-Tailored Heterogeneous Acrylate Substrate

In recent years, highly functionalized electronics with more variable form factors have attracted lots of attentions. To achieve the continuous requirement of consumer’s needs, lots of research groups and industries have focused on emerging technologies which is closely related to the development of ultra-flexible and stretchable electronics. Meanwhile, metal-oxide (MO) or amorphous oxide have been considered as a promising active semiconducting material for large-area and personal electronics due to their high carrier mobility, relatively good operational stability, high transparency, etc. The aforementioned advantages enable the MO as promising channel semiconductors in switching and driving thin-film-transistor (TFT) for flexible display, wearable devices, and smart windows. A lot of studies to implement MO semiconductor devices on elastomeric substrates become a groundwork for deformable electronics such as electronic skins and bio-integrated devices. Due to the rigid and fragile properties of the MO materials, however, direct implementation of the MO devices on highly elongated substance frequently hinders the realization of fully deformable MO integrated circuits and systems. Therefore, the bridge structure which is combined with embedded rigid islands and adjacent elongated substance is proposed. The rigid islands which have high elastic modulus protects the fragile active components from mechanical stress, which induces deviation of the posed stress into the areas adjacent the islands. Therefore, as most of the stress is concentrated on the outer wall of the rigid island, the problems like delamination or collapse of the island can frequently generated, facilitating device and system failure.<br/>In this work, we investigate highly stretchable MO TFTs and integrated circuits which are implemented on molecular-tailored heterogeneous substrate which consists of poly epoxy acrylate (PEA) and poly urethane acrylate (PUA). By employing the heterogeneous rigid-island and stretchable substance, highly reliable structures were constructed to minimize the strain applied on the fragile semiconductors and to enhance the adhesion between the rigid island and the elastomer material. Strong acrylate bonding formed between PEA and PUA prevents delamination of the active components in the circuits, avoiding device failure. For the wiring electrode, which connect individual transistor on the rigid PEA islands, intrinsically stretchable gallium-based liquid alloy (eutectic gallium indium) is employed. For the viability of the proposed architecture, various dimensional MO TFTs, 55 TFT arrays, and 7-stage ring oscillator are implemented on the stretchable substrate, exhibiting highly stretchable and almost invariant characteristics under various harsh deformation. The TFTs show minimal degradation while stretched up to 50% (m of 12cm²/Vs and Dm of 2.5cm²/Vs) and the arrays and integrated circuits operate normally under the tensile strain of larger than 30%.