Han Wang - US grants

Photonic technologies have become ubiquitous in our modern society: infrared photodetectors and modulators enable optical communications and the internet, compact cameras in mobile devices make the instantaneous recording of precious moments possible, and solar cells provide environmentally-friendly electricity. Traditional photonics technologies often use a specific material to cover a particular wavelength range, with integration of multiple types 0f photonic materials to cover a broader range highly challenging. This EFRI team will investigate fundamental optical sciences and explore practical photonic applications of a novel two-dimensional (2D) material, black phosphorus (BP), which can cover a broad wavelength range from visible to mid-infrared and can be easily integrated with other photonic platforms due to its layered structure. The team will develop approaches for large-scale black phosphorus synthesis, material characterization, and BP device realization and testing, thus establishing the foundation for black phosphorus based photonic technologies. This project will transform many technological areas relying on optical imaging, sensing and communications, contributing to the National Photonics Initiative (NPI). The team consists of five investigators from four universities (Yale University, Massachusetts Institute of Technology, University of Southern California, and Washington University in St. Louis) and covers multiple disciplines including material sciences, physics, and engineering. This EFRI program will also provide students at different levels, especially those from underrepresented groups, and postdocs with multidisciplinary research experience fostered by the EFRI team, as well as through interactions with the industrial and international partners.

This project will leverage recently rediscovered 2D layered black phosphorus to develop novel photonic devices for optical communications and infrared imaging, while exploring its integration with other 2D (e.g. graphene) and bulk (e.g. silicon) materials. In particular, the team will utilize BP?s widely tunable bandgap with layer number and its robust, anisotropic excitons to explore new optical sciences and to transform present photonic technologies. Establishing the theory, synthesis, encapsulation, and characterization approaches of few-layer and thin-film BP, as well as the fabrication and benchmarking of BP photonic device performance will build the foundation of this paradigm shift in photonic devices. Scientifically, exploration of anisotropic excitons and their tunability by electric field in few-layer BP will advance our basic understanding of many body physics in materials with low crystalline symmetry. Technologically, high carrier mobility, direct bandgap and strong light-BP interaction will enable the realization of a number of high performance BP photonics devices especially in strategically critical near- and mid-infrared wavelength range.

Establishing the foundation for electronics technology based on atomically thin two-dimensional (2D) materials, such as layered transition metal dichalcogenides (TMDCs), may prove to be transformative in many technological areas relying on flexible electronic and nanoelectronic systems. This project will establish a critical knowledge base for future 2D TMDC electronics technology for a broad range of applications, such as low power computing, flexible display, and wearable electronics. The project has a direct industrial impact through the respective collaboration and technology transfer between the participating universities and the industrial partner. It will also offer interdisciplinary research opportunities for training graduate students, as well as undergraduate and high school students, in a collaborative research environment between university and industry, and provide valuable resources for research and educational community by disseminating web-based learning modules, simulators, and experimental data on TDMC-based electronics.

While TMDC materials are promising for many potential applications in nanoelectronics and flexible electronics due to their mechanical bendability, atomically thin thickness, and excellent intrinsic carrier transport properties, major gaps exist on translating early science of such materials into practical circuit and system technologies. The objective of this project is to develop compact model and circuit-simulation platform for new 2D TMDC-based devices and systems, and to explore its applications in flexible and wearable electronic systems through experimental demonstration and collaboration with IBM T. J. Watson Research Center as the industrial partner. The proposal will undertake the following tasks: (i) develop a multiscale simulation framework that integrates atomistic device simulations with compact circuit models for TMDC transistors, (ii) fabricate, characterize and simulate basic TMDC circuits, (iii) model the variability and defect mechanisms and their correlations in TMDC transistors, and (iv) design and experimentally demonstrate TMDC driving circuits for transparent flexible display.

The semiconductor electronics technology plays a critical role in enabling many electronic systems for computation and communication applications from computers to smart phones. The study of new semiconductor materials and the innovation of new electronic device concepts are of fundamental importance in developing the future generation computation and communications technology. The research activities in this program aim to develop the foundation of the electronics technology based on the emerging semiconductor material black phosphorus and related two-dimensional materials, which can benefit many transformative technological fields utilizing low power, reconfigurable and adaptive electronic systems. This project will develop a critical knowledge base for the study of the fundamental electronic properties of black phosphorus and the exploration of novel device functionalities for applications in computation and communications. Furthermore, the program will also offer valuable research opportunities for training the next generation workforce for the semiconductor industry by exposing graduate students, as well as undergraduate and high school students, to a wide range of research opportunities with both the university research facilities and the industrial collaborator. This project will also enhance the participation of woman and underrepresented students in semiconductor electronics research. The scientific results will be disseminated through the use of scientific community website dedicated to education and research, such as nanoHUB, to share the research outcomes with the general scientific community and made them available for educational use.

Recently rediscovered black phosphorus has shown promising potential for electronic applications. With its tunable energy gap, as well as strong ambipolar conduction resulting from its moderate bandgap (0.3 eV in bulk), the material offers attractive features for exploring new semiconductor device concept for electronics application. On the other hand, despite of promising potentials, major challenges exist on translating early science of black phosphorus materials into advanced device technologies. Novel device concepts unique to black phosphorus materials, as well as their fabrication technology, remain largely under-developed. Experimental demonstrations and design innovations of devices based on black phosphorus that may lead to novel functionalities, especially with re-configurability in its operational characteristics, remain rare. The objective of this CAREER program is to reveal the tunable electronic properties of black phosphorus such as electrostatic tuning of its bandgap and ambipolar conduction, and to build transformative devices for applications in electronics. The proposed research program includes the following activities: (1) utilize electronic and optical characterization techniques to evaluate bandgap tuning and carrier transport properties in black phosphorus, (2) devise novel device concepts, leveraging tunable properties in black phosphorus, such as the ambipolar conduction, and (3) benchmark black phosphorus device performance with the current state-of-the-art, and evaluate the new functionalities these devices can enable, (4) develop theoretical device models to predict and guide basic device physics research.

PROJECT SUMMARY Sleep is a fundamental biological process that is essential for survival. Sleep abnormalities not only affect daily performance but also contribute to various diseases, including cognitive disorders and cardiovascular diseases. It is estimated that 50-70 million Americans suffer from chronic sleep loss and other sleep disorders, such as insomnia. However, effective treatments for sleep disorders are limited. Thus, it is imperative to understand the genetic basis, neural circuits and functions of sleep. Recent studies suggest that sleep is an evolutionarily conserved process, with shared features across different organisms that include behavioral quiescence, increased arousal threshold, and rapid reversibility to wakefulness. To understand the conserved mechanisms underlying sleep regulation and function, I will study a robust sleep model (EGF-induced sleep in C. elegans) that we have generated. It has been shown that epidermal growth factor (EGF) signaling promotes sleep in worms, flies, fish and mammals. In C. elegans, transient activation of EGF signaling in the neuroendocrine cell (ALA) promotes a sleep-like state. My preliminary data shows that transcriptional changes occur during EGF-induced sleep. However, the identities of sleep-promoting neurons downstream of ALA and the molecular mechanisms underlying the impacts of EGF-induced sleep on the worm?s physiology are still unknown. I hypothesize that ALA coordinates downstream sleep control center(s) to drive a sleep state, which induces transcriptional changes to impact physiology. To facilitate the identification of these downstream sleep-promoting neurons, I have developed a new bipartite expression system, called cGAL, for spatiotemporal control of transgene expression in C. elegans, similar to the GAL4-UAS system for Drosophila. With this new genetic tool, I propose to: 1) Identify the neural circuits underlying EGF-induced sleep; 2) Refine cGAL for better spatial and temporal control of transgene expression in C. elegans; 3) Determine transcriptional changes during EGF-induced sleep. To achieve these aims, I need additional scientific and technical training on RNA-seq, bioinformatics, optogenetics, microscopy and circuit mapping the bipartite cGAL system. The K99/R00 award will allow me to acquire these skills with the guidance from my mentors (Dr. Paul Sternberg and Dr. David Prober) and my advisory committee (Dr. Barbara Wold, Dr. David Anderson, Dr. Viviana Gradinanu, Dr. Andres Collazo and Dr. Igor Antoshechkin).The results of this proposal will provide a framework for my future career to focus on the study of the molecular and cellular mechanisms underlying sleep regulation and function in my own laboratory. My study will advance our understanding of the biology of sleep, which may ultimately contribute to the development of effective treatments for sleep disorders. In addition, this project will also provide the C. elegans community with a fully functional bipartite expression system through a valuable set of cGAL reagents, which will allow other researchers to dissect the neural circuits for other complex behaviors in C. elegans.

Quantum material architectures consist of graphene and other two-dimensional materials, which, when stacked in precise three-dimensional architectures, exhibit unique and tunable mechanical, electrical, optical, and magnetic properties. These three-dimensional architectures have broad potential applications and are highly promising components for microchips, batteries, antennas, chemical and biological sensors, solar-cells and neural interfaces. However, currently, due to the lack of fundamental understanding of the physical and chemical processes, it has been difficult to control or scale the manufacturing of these three-dimensional structures. This Future Manufacturing (FM) grant is to develop a transformative Future Manufacturing platform for quantum material architectures using a cybermanufacturing approach, which combines artificial intelligence, robotics, multiscale modeling, and predictive simulation for the automated and parallel assembly of multiple two-dimensional materials into complex three-dimensional structures. This platform enables future production of high-quality, custom quantum material architectures for broad and critical applications, supporting continued U.S. leadership in technology development. The research in cybermanufacturing is integrated with innovative educational programs for cross-disciplinary training of scientists and engineers, especially, women and underrepresented minorities, in advanced manufacturing, artificial intelligence and quantum structures, as well as engaging the public in future manufacturing concepts.

This grant research focuses on a fundamentally new method for scalable manufacturing of 3D quantum material architectures or van der Waals heterostructures (vdWHs) using microfluidic assembly. vdWHs are composed of unlimited combinations of atomically thin layers and exhibit interesting emerging functionalities. The key process innovation is precision microfluidic folding of 2D materials, which has been demonstrated at a small-scale. This method has promising potential to scale up to wafer scale, with no fundamental limit on scaling. A second key innovation is embedding artificial intelligence (AI) across all aspects of the manufacturing process flow, from low-level precision control, to automated characterization, to high-level structure predictions. Predictive simulation and visualization tools combined with in situ spectroscopy allow real-time analysis of atomic-scale physical and chemical processes and their control. Moreover, parallel self-assembly in microfluidic environments is investigated as a pathway toward truly scalable manufacturing. The expected outcome of the award is to produce superlattices consisting of tens of atomic layers with precisely engineered stacking order and alignment, leading to fundamentally new custom quantum material architectures with electronic and photonic properties impossible to obtain from conventional material architectures. This research advances fundamental knowledge in material physics, nanoscale electronics and photonic science leading the way to manufacturing of future devices, such as twistronics. A key outcome is an AI-driven, robotics-controlled cybermanufacturing microfluidic platform that is capable of manufacturing complex structures for emerging quantum and other device applications.

This Future Manufacturing research grant is supported by the following Divisions in the Engineering Directorate: Civil, Mechanical and Manufacturing Innovation; Electrical, Communications and Cyber Systems; and Engineering Education and Centers; and the following Divisions in the Mathematical and Physical Sciences: Materials Research; Chemistry; and Mathematical Sciences.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.