I WEI CHEN

Nanograin BaTiO3 Ceramics for Dielectric, Ferroelectric and Piezoelectric Applications (Supported by NSF (DMR), I-Wei Chen (PI) - 2009-2012)

This project seeks to systematically investigate nanograin ceramic dielectrics and ferroelectrics to explore the impact of nano structures on physical properties and device performance. The premise is that electric, dielectric, mechanical and kinetic interactions at the nano scale can interplay to create new phenomena hitherto unexplored, and that these phenomena may pertain to either new device applications or potential failure mechanisms. This interplay partly arises from the very large electric and mechanical field present in nanograin ceramics even at a low operating voltage. Examples of the research include (a) experimental characterization of transition temperatures in BaTiO3 as a function of grain size; and (b) modeling of internal electric field and mechanical field including their effects on phase stability and transition temperatures.

 

Breast Tumor Targeting, Imaging and Treatment Using a Synthetic Lipoprotein Vehicle Containing Iron Oxide and Paclitaxel (Supported by DOD (Army), I-Wei Chen (PI) - 2010-2012);  A Flexible Biomimetic Nanoparticle Platform for Targeted Imaging and Drug Treatment of Prostate Tumor (Supported by DOD (Army), I-Wei Chen (PI) - 2010-2013)

Theranostic nanoparticles are delivery vehicles that can detect and treat diseases on the same delivery platform. This project seeks to design a new theranostic platform for overcoming HER2-positive breast cancer and PSMA-positive prostate cancer with minimal side effect. This is achieved by using self-directing nanoparticles that bring image-enhancing agents and tumor-killing drugs to the breast tumor cells. By combining peptide design with lipoprotein-mimetic synthesis, we are able to incorporate imaging agent (such iron oxide), drug (such as paclitaxel), and various targeting moieties specifically tailored for individual tumors and their vasculatures, into one “theranostic synthetic lipoprotein.” The platform is flexible: it can be used to load other drugs, image-enhancing agents or targeting molecules to take advantage of future advances in biomedical research.

 

Nanometallicity in Si-based Amorphous Thin Films (Supported by NSF (DMR-EPM), I-Wei Chen (PI) - 2011-2014)

This project aims for the discovery of new random materials that exhibit metal-insulator transitions when the sample size is comparable to electron’s localization length. We have recently observed such transitions in thin films of perovskite solid solutions and of atomic-Pt-dispersed SiO2 and Si3N4. By tuning either the electron density (via composition and/or chemistry) or the random field (via charge injection/removal and/or chemistry), we can change the Anderson diffusion distance of 0K electrons, thus triggering the transition at a fixed film thickness. Voltage and photon triggered transitions in these materials have allowed us to demonstrate a resistance switching non-volatile memory with extremely uniform switching parameters. The design of these materials follows a paradigm opposite to the one prevailing in the Si-based electronic industry, which emphasizes structural perfection and chemical purity.

 

Electric-loading Enhanced Kinetics in Oxide Ceramics: Sintering, Pore Migration and Grain Growth (Supported by DOE (BES), I-Wei Chen (PI)— 2011-2014)

This project builds on our recent discovery of massive microstructure changes in 8YSZ under electric loading. Such changes include pore migration, electro-sintering and grain growth. The findings are remarkable in three respects: (a) neutral objects such as pores and bubbles can move in an uniform electric field without a direct thermodynamic force; (b) pore migration and electro-sintering can occur at low temperatures without cation lattice/grain-boundary diffusion; and (c) grain growth is position-biased even though the spatially uniform field is not. These findings may also hold for other fast ion conductors. Obviously, they have direct bearings on the reliability of electrochemical devices such as SOFC and solid state batteries.