Syntheses, Analyses and Applications of 2D Materials and Their Heterostructures
There have been a growing interest in two-dimensional (2D) crystals beyond graphene, facilitating novel electronic and optoelectronic devices. Doping different atoms into transition metal dichalcogenides (TMDs) creates 2D dilute magnetic semiconductors, promising for spintronics applications. Our work synthesizes 2D dilute magnetic semiconductors via an in situ substitutional doping of metal atoms into the transition metal lattice sites in TMD monolayers, and probes ferromagnetism at room temperature. These van der Waals ferromagnets finds critical applications, including on-chip magnetic manipulation of quantum states or spintronics. Other related projects include modeling to prevent the anomalies encountered in topographic images of TMD monolayers in dynamic atomic force microscopy, and elucidating the effect of TMD surfaces and their geometric arrangements on cellular morphology and adhesion. Suppose our growth and nanofabrication strategy could be developed to be highly reliable and high fidelity, in this case, it could have an enormous impact on the future research and commercialization of TMD-based devices.
Flexible Electrodes and Tunable Wetting
Skin-attachable electronic devices can be subjected to various lateral strains via stretching, bending, and distortion, while the devices must provide reliable outputs under pressure orthogonally applied to the surface. We perform partial-embedding of vertically aligned carbon nanotubes in polydimethylsiloxane, which are stable under stretching and bending (flexibility) for long-cyclic testing. The devices (e.g., pressure sensors) made using this process can be sensitive or insensitive to these lateral strains induced by mechanical deformation (such as stretching, bending, twisting, and wrinkling). We also utilize dodecylbenzenesulfonate-doped polypyrrole (PPy(DBS)) to provide additional functionalities to the flexible sensors and energy-storage devices. Stretchable electrodes will have applications in the fields of wearable electronics, flexible photovoltaics (e.g., rolled-up displays), self-powered wearable optoelectronics, and electronic skins.
Representative Invited Presentation slides
2D Material-based Heterostructures toward Matter Wave Interferometer (Funded by US Army): This project aims to nanofabricate 2D materials-based sensing elements using graphene to explore matter-wave interferometers. We explore the nanoscale processing and characterization techniques toward matter-wave interferometers.
Carbon Nanotube-based Sensors for Munition (Funded by US Army): This project develops stretchable strain gauges fabricated via a partial-embedding of vertically aligned carbon nanotubes in polydimethylsiloxane. This stretchable device can be used for several applications including wearables and electronic skins.
Rejuvenating Conjugated Polymer Membranes for Oily Water Treatment (Funded by ACS PRF): This project investigates self-cleaning of surfactant-doped conjugated polymer membranes and the relationship between the interface and permeation dynamics in several types of membranes.
Graphene Microstructures for Photodetectors (Funded by NSF and AFOSR): This project is to investigate the graphene microribbon arrays for applications in infrared detectors. We demonstrated fully-suspended CVD-grown graphene microribbon arrays dominated by the photoelectric effect.
Tunable Wetting on Smart Polymers for Microfluidics (Funded by NSF): The research aims to achieve controlled manipulation of liquid droplets on PPy electrodes for ultra-low voltage lab-on-a-chip devices. This investigation represents a pathfinder study aimed at future research and development in bio and energy applications.
Nanotechnology Exposure for Undergraduate Students (NUE-NEXUS) (Funded by NSF): The primary goal of this program is to create a nexus between nanotechnology and undergraduate engineering education at Stevens to expand understanding of nanotechnology and its applications to a broad undergraduate student population.
Atomic Lattice Imaging of Graphitic Materials for Advanced Nanoelectronics and Nanosensing Systems (Funded by AFOSR): This project funds the purchase of a high-resolution scanning probe microscope (SPM), capable of imaging in ambient conditions, to directly support the needs of current federally funded research programs.
Nanoimprint Lithography for Nanoscience Research and Education based on Low-Dimensional Materials (Funded by NSF): This grant funds the acquisition of a Nanoimprint Lithography System, a whole-wafer nanoimprinter for thermoplastic resins that has high-resolution and high-throughput capabilities.
Carbon-based Electron Wave Interferometer (US Army ARDEC): This project explores the nanoscale processing and characterization techniques toward matter-wave interferometers.
Ultra-Low Leak Rate Piezoelectrically actuated Microvalves for Controlled Sampling by Mass Spectrometers (NASA GSFC IRAD) (PI: Balvin, NASA Goddard Space Flight Center): This project is to develop piezoelectrically actuated microvalves for controlled sampling by mass spectrometers for NASA applications.
Graphene as Transparent Conductive Electrodes for High-Density Focal Plane Assemblies (NASA GSFC IRAD) (PI: Li, NASA Goddard Space Flight Center): This project develops graphene growth technology and helps GSFC to build the CVD system to grow graphene.
Micromachined Piezoelectric Multi-layer Actuators for Cryogenic Adaptive Optics (NASA SBIR Phase I and II) (PI: Jiang, TRS Technologies): This project is to develop micromachined piezoelectric actuators for cryogenic Adaptive Optics toward NASA applications.
Single Electronic Memory Devices based on Carbon Nanotube Quantum Dots (Funded by AFOSR): This project investigates to investigate carbon-based transistor devices. Quantum dot-based electron transistor devices were successfully fabricated and demonstrated.
Inchworm microactuator (Funding: National Reconnaissance Office, NASA): 2001~2005
MEMS Adaptive optics (Funding: Center for Adaptive Optics, JPL Director's Research and Development Fund, DARPA/LASSO): 1999~2006
Actuated membrane development (Funding: National Reconnaissance Office): 2003~2004
Piezoelectric microvalve (Funding: NASA Code R Enabling Technology Thrust): 2001~2004 (Market Analysis)