(3gi) Hierarchical Structure Design of Soft Materials for Unique Properties

I am interested in developing new and advanced soft materials with unique electronic, optical, and mechanical properties. Advanced characterization techniques (electron microscopy, spectroscopy, small angle X-ray, light and neutron scattering) will be used to attain fundamental understanding and to develop general guidelines for producing well-controlled colloidal structures over multi-length scales. In particular, scattering-based techniques allow time-resolved characterization that captures in-situ structural changes and provide quantitative analysis of samples. Structure-property relationships will be established for these materials. The formation mechanism, phase behavior and kinetics are critical aspects of colloidal materials to optimize their performance for use in a broad range of applications, such as energy storage, wearable sensors, and stimuli-responsive devices. Soft matter possesses opportunities for the discovery of novel functional materials and I am enthusiastic to collaborate with other experts to promote the development of this field.

The understanding of the structure-property-relationship in multi-length scales is crucial in developing the next-generation functional materials. This is especially true for soft materials, such as polymers and colloidal gels, due to their large design freedom and, at the same time, great challenges in forming well-controlled structures. Hierarchical structure design has widely revolutionized the fields of energy, nanotechnology and biomedical applications with novel materials or intriguing properties. My previous research experience emphasizes the critical role a thorough understanding of structures plays in material design. The multi-length scale information from scattering techniques is analyzed and served as a guideline for formulating strategies to assemble materials with specific properties. Not only desired structure can be achieved, stimuli-responsive materials with on-demand tunability of properties is also obtained.

Teaching Interests:

I am interested in teaching core chemical engineering classes, such as kinetics and thermodynamics. Besides, my specialized training is in colloids and interfacial science and I am also interested in teaching related classes. I spent two semesters teaching colloids and interfacial science laboratory and two semesters teaching unit operation laboratory. Aside from those, I also mentored graduate and undergraduate students in the past in my research group. While working as postdoctoral researcher at National Institute of Standards and Technology, I also participated in mentoring an undergraduate researcher in a collaborative research project.

Despite what class I will be teaching, my goal is to help students succeed, both in classroom and moving beyond. I believe that effective teaching exists in different styles and various forms. Being a student and a researcher throughout the years, I witnessed many ways of teaching. At the same time, as a teaching assistant myself, I also had my own thoughts from a different point of view on promoting the learning experience of students. Thus, I am eager to apply what I have learnt to motivate students to be life-long learners, encourage them to learn with positive attitude, and foster independent practices, as well as interactive communications.

Successful Proposals:

Experimental proposals that have been granted beamtimes from synchrotron- and neutron-based national labs, including 8 proposals to NIST Center for Neutron Research (NCNR), 3 proposals to Argonne National Laboratory, 2 proposals to Brookhaven National Laboratory, and 1 proposal to Oak Ridge National Laboratory (ORNL).

Postdoctoral Project:

“Porous materials under extreme conditions”

Under supervision of Yun Liu,

1. NIST Center for Neutron Research
2. Department of Chemical & Biomolecular Engineering, University of Delaware

PhD Dissertation:

“Structure Engineering of Self- and Directed-Assembled Conjugated Polymers”

Under supervision of Lilo D. Pozzo, Chemical Engineering, University of Washington

Committee members: Christine K. Luscombe, Stuart Adler, and Lih Lin

Research Experience:

My research experience is mainly focused on interdisciplinary fields involving materials, physics and engineering. I was trained in the field of colloidal science with an emphasis of structural characterization using scattering techniques. In order to achieve different functions, the assembly of materials is controlled to realize specific structures. My previous research experience is focused on the assembly of polymers and colloidal particles. External electric and acoustic fields are demonstrated to guide conductive polymers to grow into aligned structures or fibers with high aspect ratio. The charge transport is thus enhanced. By carefully engineering the solvent-solvent and solvent-solute interactions, a ternary system can be designed to not only achieve desired structures, but also obtain stimuli-responsive materials with on-demand tunability of properties. I have learned the fundamental physics behind the assembly of polymers and nanomaterials, which can be used to achieve unique functions with hierarchically engineered structures. I acquired the knowledge and invaluable experience by closely working with instrument scientists in national labs while conducting experiments. At the same time, the purpose of engineering structures is to obtain unique functions. The projects that I worked on always involved collaborations and closely related fundamental science to applications. Examples include photovoltaics, transistors, sensors, optoelectronics, batteries and biomimetic materials.

Selected Publications:

Yuyin Xi, Yun Liu, “Tunable thermo-reversible bicontinuous nanoparticle gel driven by the binary solvent segregation”, submitted.

Yuyin Xi, Caitlyn M. Wolf, Lilo D. Pozzo, “Self-assembly of Donor-acceptor Conjugated Polymers Induced by Miscible Poor Solvents”, Soft Matter, 15, 1799, (2019).

Yuyin Xi, David S. Li, Greg M Newbloom, Wesley K Tatum, Matthew O’Donnell, Christine K. Luscombe, Lilo D Pozzo, “Sonocrystallization of Conjugated Polymers with Ultrasound Fields” Soft Matter, 14, 4963, (2018).

Yuyin Xi, David S. Li, Yi-Ting Lee, and Lilo D. Pozzo, “In-Situ Ultrasound sample environment for small angle scattering studies” 2018 NCNR Highlight (2018).

Yuyin Xi, Lilo D. Pozzo, “Electric Field Directed Formation of Aligned Conjugated Polymer Fibers” Soft Matter, 13, 21, 3894, (2017).

Yuyin Xi, Yueh-Ling Hsieh, Ya-Hsi Hwang, Shun Li, Fan Ren, Stephen J Pearton, Erin Patrick, Mark E Law, Gwangseok Yang, Hong-Yeol Kim, Jihyun Kim, Albert G Baca, Andrew A Allerman, Carlos A Sanchez “Effect of 5 MeV proton radiation on DC performance and reliability of circular-shaped AlGaN/GaN high electron mobility transistors” Journal of Vacuum Science & Technology B 32, 012201(2014).

Yuyin Xi, Lu Liu, Fan Ren, Stephen J Pearton, Jihyun Kim, Amir Dabiran, Peter P Chow, “Methane detection using Pt-gated AlGaN/GaN high electron mobility transistor based Schottky diodes” Journal of Vacuum Science & Technology B 31, 032203(2013).

Yuyin Xi, Lu Liu, Ya-Hsi Hwang, Oluwadamilola Phillips, Fan Ren, Stephen J Pearton, Jihyun Kim, Chien-Hsing Hsu, Chien-Fong Lo, Jerry Wayne Johnson, “Study of hydrogen detection response time at room temperature with Pt-gated diodes fabricated on AlGaN/GaN hetero-structure” Journal of Vacuum Science & Technology B 31, 032202(2013).

Jiangsheng Yu, Yuyin Xi, Chu-Chen Chueh, Jing-Qi Xu, Hongliang Zhong, Francis Lin, Sae Byeok Jo, Lilo D Pozzo, Weihua Tang, Alex K-Y Jen, “Boosting Performance of Inverted Organic Solar Cells by Using a Planar Coronene based Electron-transporting Layer” Nano Energy, 39, 454, (2017).