Self-assembled superlattices for flexible and wearable electronics
The self-organization of molecular, nano, and larger building blocks into complex structures is a process that widely occurs in nature. In biological systems, for example, the interaction and organization of DNA, proteins, cells, etc., determines the complicated biological functionalities, such as photosynthesis in plant leaves, signal transduction in neurons, and intelligence in brains. Such self-assembly processes often have higher energy and materials efficiency than artificially built systems, such as computers and robots. It is thus tempting to construct artificial electronic systems utilizing self-assembly, to achieve both higher efficiency, and flexible structures that can be integrated with human body.
The Illinois MRSEC team tackled this problem. Yingjie Zhang (Beckman Fellow), Nadya Mason (I-MRSEC director), Matthew Gilbert (I-MRSEC PI) and co-workers discovered that a two dimensional superlattice structure made from self-assembly can enable tunable electronic functionalities. They constructed such a flexible electronic system by putting graphene on top of a close-packed array of SiO2 nanospheres (20 nm diameter). Due to a spatially varying graphene-nanosphere interaction force, the graphene lattice is periodically deformed, forming a strain superlattice. This periodic structural modulation induces destructive electron interference at certain energies, similar to the way light is diffracted by optical gratings. Moreover, the energy spectrum of electrical conductance can be further tuned by modulating the magnitude of lattice deformation. This flexible, self-assembled superlattice allows facile integration with human body, and can enable a variety of wearable electronics technologies, such as motion sensors and infrared cameras.