Synthesis of Nanomaterials:
A high degree of control over the size, structure and composition of nanocrystals is essential to tailoring the chemical and physical properties for the target application. HybridNano laboratory conducts research to control the change of surface energy and the final shape of the nano materials according to various synthetic conditions. In particular, 2D nanocrystals of various sizes have been actively studied because they have unique electrical, optical and thermal properties. 2D thin films offer great potential for a variety of applications including future electronics, optics, energy storage and catalysts. The HybridNano laboratory synthesizes high-quality oxide thin films, 2D semiconductor material thin films, and metal thin films on desired substrates. In particular, we are focusing on synthesizing single crystal thin films with excellent electrical properties.
Stretchable Devices:
HybridNano laboratory analyzes the characteristics of polymers, metals, semiconductors, and ceramics. We futher analyze the compatibility between them, and test the mechanical and electrical properties of materials during stretching. We fabricate devices such as stretchable sensor, display, transistor, diode and battery.
As methods of fabricating basic elements for stretchable devices, three approaches (structural methods, polymer composites, liquid metal) are mainly used. For structural methods, understanding of the mechanical behavior and stress distribution of a structure is important. We fabricate and test structures and conduct computer-based simulation analysis through cooperative research. In the case of polymer composite fabrication, we develop new materials and analyze the properties of the developed materials by considering the compatibility, modulus, bonding force, and reactivity between polymer and other materials (metal, semiconductor, ceramic). For liquid metals, we analyze how to pattern and interface with other materials. We develope next-generation electronic devices by integrating basic devices such as electrodes and sensors. We aim to produce skin-attached and implantable stretchable device platforms.
Electronic Skin:
Human grasps an object by aid of pressure information transmitted from the tactile receptors on the fingertips and perceives the external temperature from the skin's temperature receptors. As such, stimulus receptors are essential to understanding the external environment and responding appropriately. Electronic skin (e-skin) is an artificial skin designed to measure the stimulation of the five senses. E-skin contributes to the recognition of the stimulation by incorporating it for intelligent robots and prosthetic arms.
In order to mimic the real human skin, e-skin needs to be mechanically deformable and functionally capable of converting mechanical, chemical, thermal and optical stimuli into electrical signals. Polymers can be mechanically deformable according to its chemical structure, so they are mainly used to assign deformability to e-skin. Various materials such as metals, oxides, polymers, and ions are combined with polymer to realize stimulation sensitivity. The electrical property of the composite material changes as the stimulus is applied to e-skin, and the stimulus is recognized by measuring it. We aim to develop electronic skin that has higher sensitivity and mechanical deformability through optimization of material design
Micropatterning and Particle Assembly:
Patterning is a crucial technology for device fabrication and is used in a variety way as well. Integrating circuits for stretchable electronics requires reliable efficient patterning process, we are developing nozzle printing and screen printing with conductive ink. Controlling the characteristics of the ink is a key for the process development. Additionally, we produce patterns by capillary force lithography, micro-imprinting, and photolithography, etc.
Microparticle assembly has an effective way in both research and industry. Via simple mechanical rubbing process, microscale-powders can easily form a high-crystallinity monolayer over large area. This assembly has special optical properties, such as photonic crystal. The reflected light color varies depending on the crystal orientation of the particle assembly. In addition, the position registry and the deformability are guaranteed with the physical/chemical patterning on the substrate. The microparticle assembly can be suggested as one of the methodologies for fabricating stretchable devices that are being actively developed by the electronics around the world.