Shape Morphing Technology Based on a Plastic-Elastomer Framework for 3D Electronics

Three-dimensional electronics provide a strong advantage in the omnidirectional capability in sensing, displaying, communicating, and others. When direct device fabrication on 3D structures is extremely difficult, three-dimensional transformation technology based on a supporting substrate that mounts the planar membrane-type electronics becomes an excellent indirect method. When plastics are used for an additional substrate, the materials guarantee overall mechanical stability but allow only a small strain range. On the other hand, elastomers allow a large amount of strain but seem to be very soft mechanically. This study demonstrates a means of developing a plastic-elastomeric framework to achieve three-dimensional (3D) electronics with non-zero Gaussian curvature without losing mechanical stability. When using two controversial materials, it is important to guarantee the interfacial adhesion between the two materials and the possibility of controlling the shape transformation. To address the first issue, we used a self-assembled monolayer assembly that chemically bonds the two materials to guarantee strong interfacial adhesion. Regarding the second issue, we used shear-printed plastic lines to provide a driving force for automatic 3D transformation during thermal relaxation above the glass transition temperature and the elastomeric films to provide a basis for mounting the membrane electronics and allow a large amount of strain for complex 3D shapes. In a detailed study, we examined the shape morphing based on geometrical and mechanical parameters such as annealing temperature, annealing time, and other control parameters, including shear rate, line pitch, and relative thickness of plastic/elastomeric structure. In particular, we have successfully developed unusual 3D shapes such as cone, dome, and saddle shapes, among shapes predicted through mechanical finite element method simulation. To validate the feasibility of this strategy in 3D electronics, semiconductor-processed electrodes and indium-gallium-zinc-oxide transistor arrays were mounted on a plastic-elastomeric framework to demonstrate a 3D-shaped membrane electronics device.