Department of Chemical and Biological Engineering

Our group focuses on developing high performance wearable electronic devices which are integrated with diverse nanomaterials with target-specific functionalities. Specifically, we aim to develop technologies for high- performance flexible and stretchable electronic devices by using high quality nano-scale materials, which enable new biomedical and energy systems with innovative/multiple functions. The technologies will provide soft, conformable devices that can establish intimate contacts to curvilinear surfaces of native tissues in vivo, without causing any damage or alteration in the tissue, with important, clinically relevant modes of use. These advanced technologies will improve current surgical capabilities and/or invent new and unprecedented medical systems, which are important tools in clinical procedures and surgeries, for patients. Furthermore, these technologies also create low-cost energy harvesting and light emitting devices using nanostructured electronic materials and unconventional processing technologies with hopes to generate electricity with easy accessibility for all the people in the world, especially for the developing world.

The Electronics Processing Research Laboratory was established in 1999. Since then, 160 SCI papers, 93 patents, and 199 conference presentations have been accomplished. The research area can be classified as the metallization in semiconductor process, chemical mechanical polishing (CMP), and electrochemically synthesized catalysts used for gas reduction or lithium secondary batteries. As the dimension of semiconductors is shrinking, the nano-filling capability of the trench and via becomes very critical issue in metallization fabrication. As a research area of our laboratory in semiconductor process, the Cu deposition and filling by using electrodeposition and electroless deposition are focused. In particular, filling of through silicon via (TSV) is investigated as a promising technology for next-generation 3D interconnections. The electrolytes used in the filling are monitored by the cyclic voltammetric stripping (CVS) method. The CVS method is also developed to confirm the changes in the composition of organic additives. As a subsequent metallization process, the removal of overdeposited Cu is another research field, that is, CMP. Moreover, the electrocatalysts for gas reduction and Li-secondary batteries are investigated to increase the catalytic activity by using electrochemical methods. In the area of gas reduction, the gas reduction system is being manufactured by Couette-Taylor vortex flow, which demonstrates the higher performance compared to the conventional batch reactor by considering high reduction reaction rate.

We are interested in studying nanomaterials by an advanced in situ microscopy equipped with a capability of sub-nanometer scale spatial resolution, msec time-resolution to capture real time reactions, and 3D atomic resolution for realistic structure investigation all in native conditions. Fundamental mechanisms underlying in chemical reactions of nanomaterials are obtained from the in situ microscopy and utilized for precisely controlled synthesis of materials and fine engineering of their electrochemical, catalytic, and optical properties in applications. Broad research areas of interest in our research group include: (1) liquid phase / in situ transmission electron microscopy (TEM) study for nanoparticle chemistry; (2) development of microscopy and image big-data processing algorithm to investigate 3D atomic structures of nanomaterials; (3) mechanistic understanding driven synthesis of nanomaterial for engineering applications in energy conversion and catalysis.

Our group research is focused on the application of electrochemical methods with (opto)electronic and ionic materials and the realization of devices and systems. We perform research on fuel cells, batteries, and photoelectrochemical cells. Our goal is to develop high performance electrochemical technologies that are miniaturized, low cost, durable and environmentally safe. Fundamental studies of the solid/liquid interface, in situ analysis, and electrochemical nanotechnology are also carried out.

Our research area is electrochemical engineering related to the development of electrochemical energy storage devices including Li-ion batteries, Na-ion batteries, Li metal batteries (Li-S, Li-air), Mg batteries, and Redox flow batteries. Our research activities are centered on: i) understanding fundamental electrochemical behaviors of intercalation and conversion materials, such as reaction and failure mechanisms, with emphasis on interfacial chemistry regarding ionic transport between solid (electrode) and liquid (electrolyte); ii) searching for new charge storage materials focusing on the relationship between crystal structure and conduction mechanism; and iii) applying fundamental understanding to design new materials and electrochemical systems showing excellent performance. The ultimate goal of our research is the development of new innovative electrochemical energy storage systems with high energy density pursuing for a safe, clean, and more efficient energy system.

Our lab is aimed at designing and synthesizing new inorganic and organic/ inorganic hybrid materials and developing their device fabrication processes. We specialize in metal chalcogenide and halide compounds. In particular, we focus on discovery of new materials that can contribute to solving energy, environmental, and fundamental problems of condensed matter physics. Our representative research topics are as follows: i) highly performing, environmentally friendly new thermoelectric materials and devices; ii) next generation solar energy harvesting materials and their devices; iii) visible/near infrared-responsive porous semiconductors for photocatalysis, nuclear waste/heavy metal remediation, and selective capture, storage, and conversion for gases. We are also developing core processing technologies to commercialize our new materials based on our deep understanding and insights on synthesis of inorganic materials.

Research by our CRI (Creative Research Initiative) Center mainly focuses on the fundamental and applied aspects of thin films and nanopatterns involving macromolecules and functional nano-objects. The current emphasis of our research program is placed on the fabrication and characterization of block copolymer thin films, ultrathin functional multilayer films, nanoporous thin films, hybridization, and their applications to energy and environmental issues. Our research center has already established synthetic schemes to prepare well-defined nanomaterials such as block copolymers, semiconducting nanocrystals, organosilicates, and hollow metal oxide nano-objects, sulfur-based materials with various functionalities. Furthermore, fundamental knowledge on the interfacial manipulation at the molecular level accumulated in this research center can be directly applied to realize integrated devices or hierarchical structures with unique functions.

We perform research to understand the fundamental aspects of battery materials and their behavior in electrochemical processes. We not only pursue to develop high performance components for battery cells but also employ a variety of analytical tools to understand underlying phenomena in the multi-scales across atom, molecule, lattice, cell, and pack levels. Detailed research topics include silicon anode, lithium metal anode, high-nickel cathode, and electrolyte additive, etc. in the category of lithium-ion batteries. We are also involved in research for post-lithium-ion batteries, such as all-solid-state batteries, aqueous batteries, lithium-sulfur batteries, organic batteries, multi-valent batteries, etc. Besides the material-related research, we engage thermodynamics to monitor and control battery electrodes in a nondestructive fashion under a theme of developing material-based battery management systems.

Our research has been focused on the large-scale synthesis of uniform-sized nanoparticles, their designed assembly, and medical & energy applications.