Random access water-assisted transfer printing and three-dimensional thermoplastic transformation of membrane-type electronic devices

Abstract

The advent of hyper-connected society generally requires the ability to provide automatic functions to various objects, including human skin, clothes, organs, and internal/outer of buildings, forests, oceans, and spaces. The system is possible by developing electronic devices that promise both high performance and other functionality, including randomly accessible transfer printing onto complex shapes or deterministic transformation into desirable three-dimensional (3D) shapes. However, technology confronts two challenging issues. The first is the ability of conformal transfer printing to target surfaces with extremely complex surfaces with nanoscale roughness. The second is the possibility of transformation from planar to curvilinear forms without losing mechanical and electrical stability. The transformation becomes exceptionally challenging for the case of developing image sensors or displays system, which requires placement of an electrically active layer on the top surface, in other words, out of the mechanical neutral plane. The thesis addresses the issues by systematically combining the membrane-type electronics and further introducing an additional substrate that plays an essential role of either random accessibility in transfer printing or deterministic shape transformation. Chapter 1 in this thesis overviews the recent study of transfer printing and transformation technologies developed so far. In particular, this chapter highlights the randomly accessible electronics based on nanotubular cilia (NTCs) and 3D transformation technology that are addressed by Dr. Youngkyu Hwang and Dr. Hun Soo Jang. Their works confine the application level up to metal electrodes only, over which this thesis addresses mechanical and electrical aspects in transistor levels based on indium gallium zinc oxide (IGZO) in the following chapters. Chapter 2 depicts the methodology of combining a membrane-type electronic device in the transistor level with NTCs underneath the device layer. The challenging issue is to mechanically and chemically laminate the device and cilia layers without extracting water because natural drying conditions for the lamination process may cause unwanted pairing of cilia, which hampers the ability of individual movement and attachment onto complex surfaces. Another problem is the stress concentration during the lamination process because the electronic device layer itself cannot survive in thermal or chemical expansion/shrinkage during processing. In this study, tempera freezing water for transient handling medium and the use of photo-curable polymers shows reliability in the lamination process and further random access transfer printing. Chapter 3 discusses the methodology of combining IGZO transistor arrays with a spatially designed ABS polymer framework by extrusion shear printing and shape transformation by thermal plasticization method, which is one of the approaches to reduce Young’s modulus and the reflow of polymer chains. This method offers the freedom of positioning the electronic device layer, even the top of the framework. Chapter 3 also includes mechanical analysis based on the finite element method on the device level in IGZO.