- Chemical Engineering
Top 3 Areas of Expertise:
My PhD research mainly focuses on the material study and device fabrication using CVD grown conjugated polymers. For a detailed description of my PhD work, please see the thesis abstract attached.
In the future, I would like to carry research towards:
1. Material development:
Material synthesis and study for conjugated polymers and other soft semiconductors, with special focus on their thermal and electrical properties, and the related theoretical modeling.
2. Flexible circuit development:
Fabrication of flexible electronics and circuits using newly discovered high performance soft materials. The targeted applications include energy harvesting, photovoltaic, energy storage, flexible wireless sensing network (WSN), and soft robotics.
3. Machine learning assisted material design:
The main goal is using machine learning (ML) as a powerful tool to facilitate the process of conjugated polymer discovery. There are two stages of the project: 1. predicting interested properties of new conjugated polymers using known experimental data, and additional knowledge; 2. generating new molecular structures from the ML algorithms. The results of ML can guide the experiments which will be conducted by my future team. In addition, ML can potentially discover new chemistry as well. And the experimental results in my future team, in turn, will improve the development of the ML algorithms.
I would be happy to teach chemical engineering core classes, including transport phenomena, thermodynamics, reaction engineering and numerical methods. Other classes such as polymer chemistry and polymer physics also fit my background. I had experience working as a teaching assistant with Professor Deen and Professor Braatz teaching graduate level analysis of transport phenomena at MIT.
I would also be happy to design and teach new classes, such as metallic/semiconducting polymers, chemical and biological sensors, solid state physics for chemical engineers, or applications of machine learning in chemical engineering.
Expected date of graduation:
Conjugated polymers possess outstanding properties including high electrical conductivity (in the doped state), tunable band gap, and the ability to emit and absorb a wide spectrum of light. Hence, they are widely used for applications including artificial skin, organic photovoltaics (OPVs), organic light emitting diodes (OLEDs), energy storage devices, and flexible sensors. Recent investigations also show that conjugated polymers display great potential to exhibit high thermal conductivity, and thus are promising candidates for next-generation soft heat transfer materials. My PhD research focuses on three branches of conjugated polymer study. First is the synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) thin films possessing ultrahigh conductivity and mobility, complemented by theoretical modeling based on Boltzmann transport and wafer scale device fabrication of radio frequency AC to DC rectifier. Second is achieving record high cross-plane thermal conductivity (>10x common polymers) using undoped poly(3-hexylthiophene) (P3HT) thin films along with theoretical modeling. Third, is the fabrication of chemical sensing devices, using various nanostructured PEDOT and related copolymers, and the integration of the sensing devices in printed circuit boards (PCBs). Oxidative chemical vapor deposition (oCVD) is used as the synthesis method for the aforementioned polymers. As a solvent free method, oCVD circumvented the problem of low solubility of conjugated polymers and compatible issue between substrate and the solvent. In addition, the unique growth mechanism of oCVD P3HT synthesis essentially enhances the thermal conductivity. oCVD also makes it easy to pattern the polymer film during device fabrication, and provides conformal coating on nanostructured scaffolds. In addition to my three primary focus areas, side projects during my doctoral research include collaborative work with Eni S.p.A on large-scale flexible photovoltaic fabrication; collaborative work with the Department of Electrical Engineering and Computer Science at MIT on flexible energy harvesting device fabrication; DFT calculations and machine learning assisted monomer selection for light emitting polymers.
Top 5 Awards and honors (name of award, date received):
5 Recent Papers:
Wang, X.; Ermez, S.; Goktas, H.; Gradečak, S.; Gleason, K., (2017), "Room Temperature Sensing Achieved by GaAs nanowires and oCVD Polymer Coating", Macromolecular Rapid Communications, 38(12), 1700055
Wang, M.,†; Wang, X.†; Moni,P.†; Liu, A.; Kim, D.; Jo, W.; Sojoudi, H; Gleason, K. , (2017), "CVD Polymers for Devices and Device Fabrication"(†contributed equally), Advanced Materials, 29(11), 1604606
Wang, X.; Ugur, A.; Goktas, H.; Chen, Nan.;Wang, M.; Lachman, N.; Kalfon-Cohen, E.; Fang, W.; Wardle, B.; Gleason, K., (2016), " Room Temperature Resistive Volatile Organic Compound Sensing Material based on a Hybrid Structure of Vertically Aligned Carbon Nanotubes and Conformal oCVD/iCVD Polymer Coatings", ACS Sensors, 1(4), 374-383.
Wang, X.; Hou, S.; Goktas, H.; Kovacik, P.; Yaul, F.; Paidimarri, A.; Ickes, N.; Chandrakasan, A.; Gleason, K.,(2015) ,"Small-area, Resistive Volatile Organic Compound (VOC) Sensors using Metal-polymer Hybrid Film based on Oxidative Chemical Vapor Deposition (oCVD)", ACS Applied Materials and Interfaces, 7(30), 16213–16222
Wang, X.; Zhang, X.; Sun, L.; Lee, D.; Lee, S.; Shao-Horn, Y.; Dinca, M.; Palacios,T.; Gleason, K. "Ultrahigh Electrical Conductivity of oCVD PEDOT Thin Films and the Wafer Scale Fabrication of the 13.6MHz Rectifiers based on the PEDOT-Si Diode", (In submission)