Biomedical Engineering

Research Interests:

One of the long-standing challenges in materials science is the control of molecular packing during processing. With the advent of new application areas (e.g. soft electronics, energy storages, bio-interfaces) for emerging polymeric materials (e.g. conjugated polymers, charged polymers, biodegradable polymers) which leverage their characteristics of mechanical softness, electronic functionality, and biological compatibility, this challenge has resurged into prominence. My research aims to utilize the basic and neoteric principles in both polymer physics and chemistry to control the polymer organization at multiple length scales, exploring the unique properties and new potentials of polymer-based electronic materials for bioelectronics. In particular, my career objectives will focus on three areas: 1) kinetically engineering the polymer packing structure for high performance bioelectronics; 2) understanding the structure-property relationships of electronic polymers under processing and deformation by advanced in-situ characterization; 3) building an automated self-learning processing platform for multifunctional thin films, and seeking their high-profile processing-morphology-property relationships and peak performance.

Short Independent Research Summary: “Developing autonomous engine for solution-processable multifunctional materials”, Argonne National Lab

Postdoctoral Research Summary: “Applying polymer physics concepts to realize integrated, intrinsically stretchable transistors for skin electronics” Advisor: Zhenan Bao (Chemical Engineering), Stanford University

PhD Dissertation: “Molecular packing structures and dynamic behaviors in confined soft matters” Advisor: Xue Gi, School of Chemistry and Chemical Engineering, Nanjing University

Research Experience

My academic trainings and research experiences focus on polymer physics, fundamental understanding of molecular organization, the coupling between mechanical and electronic behaviors, and the development of innovative processing methodologies for functional materials.

I am currently an assistant scientist at Argonne National Lab since 2018. I received my PhD degree from the School of Chemistry and Chemical Engineering at Nanjing University in 2014, with a focus on the understanding of molecular packing structures and dynamic behaviors in confined soft matters. In my subsequent postdoctoral training with Prof. Zhenan Bao at Stanford University, I have applied my solid background in polymer physics to the emerging field of skin-like electronics, with the development of a new class of stretchable electronic materials and the realization of integrated, intrinsically stretchable transistors and circuits. Started from October 2018 at Argonne as an PI, I have been developing a new platform that combines artificial intelligence (AI) and robotics to leverage computational (synthetic) and experimental (e.g. morphological structures, solid properties) data to reveal mechanisms, parse the fundamental underlying laws, and AI-based feedback to guide material processing.

Beneficial from my knowledge in polymer physics gained from my PhD research, I have generated a physics concept - nanoconfinement effect - to increase polymer chain dynamics in semiconducting materials and developed a stretchy transistor that can be elongated to twice in its length with only minimal changes in its conductivity was created (Science 2017). Later on, again based on polymer physical phenomenon – phase separation, I have invented a new manufacturing process that can introduce multi-scale morphological ordering in stretchable semiconductors and boost their electrical performance by six-fold (Nature Materials 2019). This is the first time that a mass fabrication method - roll-to-roll coating - is successfully applied to fabricate active layers for stretchable electronics in meter-scale. Furthermore, my college and I co-lead a project which realized the first success in the development of the core elements for skin-like electronics—intrinsically stretchable transistor array and thus circuits, through an unprecedented scalable fabrication platform that possesses universal applicability to stretchable polymer materials, high yield and device uniformity (Nature 2018). This intrinsically stretchable transistor array and its fabrication platform developed hold the core position in the interdisciplinary area of intrinsically stretchable electronics, by bridging the material research to the electronics and application development.

Teaching Interests:

Throughout my 10 years as a student then a postdoc in Chemical Engineering Department, I have been guided and inspired by numerous great mentors and teachers, whose teaching philosophy has helped shaping that of my own. At Nanjing University, I have TAed undergraduate level classes in analytical chemical projects laboratory. At Stanford, I seized every opportunity to further enrich my learning and teaching experiences since the first day I arrived. Specifically, I actively attended many classes, such as Polymer Chemistry (CHEMENG 464), Organic semiconductors for Electronics and Photonics (MATSCI 343), Polymer Physics (CHEMENG 466). I’m constantly inspired by the professors’ skills to stimulate the students’ enthusiasm for learning. In addition to this effectiveness in the classroom, I equally value my mentorship ability in the lab. As a graduate student, I mentored three junior graduate students. One of them has obtained her Ph.D. with University President’s Honor. As a postdoctoral scholar at Stanford, I mentored three master students, two of them successfully obtained Ph. D. offers from Stanford.

Thus, based on my extensive training in interdisciplinary fields including polymer science, chemistry, chemical engineering, electrical engineering and nanotechnology, I am interested in and capable of teaching several areas within Chemical Engineering at both undergraduate and graduate levels, including the courses in the subjects of thermodynamics, kinetics, polymer materials, nanomaterials, electronic materials & devices, semiconductor physics, etc. I welcome the opportunity to develop a new graduate elective course on microstructure evolution and characterization of electronic materials for Chemical Engineering.

Selective Publication List (24 articles in total, citation: 2104) (# indicates co-first author and * indicates corresponding author)

1. Xu, J. #; Wang, S. #; Bao, Z.*; et al., Highly stretchable polymer semiconductor films through the nanoconfinement effect. Science 2017, 355(6320): 59-64.

2. Wang, S. #; Xu J. #; Bao, Z.*; et al., Skin electronics from scalable fabrication of an intrinsically stretchable transistor array. Nature 2018, 555, 83

3. Xu, J.#; Wu, H.-C.#; Bao, Z.*; et al., Multi-scale ordering in highly stretchable polymer semiconducting films. Nature Materials 2019.

4. Wang, S. #; Oh, J. Y. #; Xu J. #; Bao, Z.*; et al., Skin-Electronics: An Emerging Paradigm, Accounts of Chemical Research 2018, 51, 1033-1045

5. Li X. #; Xu J. #; Xue, G. *; et al., Low-temperature processing of polymer nanoparticles for bioactive composites. Journal of Polymer Science Part B: Polymer Physics 2016, 54(24): 2514-2520.

6. Xu J.; Xue, G. *; et al., Sensitive characterization of the influence of substrate interfaces on supported thin films. Macromolecules 2014, 47(18): 6365-6372.

7. Xu J. #; Diao Y. #; Xue, G. *; Bao, Z. *; et al., Probing the interfacial molecular packing in TIPS-pentacene organic semiconductors by surface enhanced Raman scattering. Journal of Materials Chemistry C 2014, 2(16): 2985-2991.

8. Xu J.; Xue G. *; et al., Detection of interchain proximity and segmental motion of polymer glass. Macromolecules 2011, 44(18): 7445-7450.

9. Xu J., Chung J., Bao Z., “Stretchable Organic Semiconductor by Blending Method.” U.S. Non-provisional Application. Atty. Dkt. No. 15639-000302-US-01, filed April 2017

10. Xue G., Li X., Wang X., Zhou D., Xu J., Teng C., Li L., “Preparation method of bioactive molecule and macromolecule composite material”, publication number CN 105385057, published March 2016