1. Wearable e-Textiles for Wireless Health Monitoring:
2. Flexible Solar/Battery Nano-Textile
Solar energy, as a clean and renewable resource, is heavily untapped, mainly due to the high cost (>$2 per watt) and low conversion efficiency (~20% for silicon) of today’s PV devices. This project aims at reducing the manufacturing cost of PV devices, by finding a scalable transparent electrode for replacing metal fingers or indium tin oxide (ITO) electrodes of conventional devices. We deposit nanocomposite fibers (NFs) with embedded conductive nanotubes (NTs) and nanowires (NWs) using novel electrospinning process that provides multiscale ordering and alignment in the structure of the NF mesh, similar to veins of a leaf (below). The process is scalable to substrates including plastic, paper and fabric, in a roll-to-roll manufacturing system. Challenges for integration of the NF mesh with Si and thin-film PV panels are being investigated to achieve the required properties at low cost.
2. Nanowire (NW) Growth and Device Fabrication:
Semiconductor and metallic NWs have unique electrical and optical properties not present in the bulk. We grow different NWs with controlled morphology using chemical vapour deposition and other growth techniques. We also work on integration of these nanomaterials into large area electronic devices, including transistors, strain sensors, bio-sensors, photodetectors, and solar cells. Materials of interest include Si, Ge, ZnO, and GaAs.
3. Flexible Organic Solar Cells:
Organic semiconductors can be deposited at low temperature on a variety of substrates. We investigate the aging and annealing effects in these materials and how the morphology of these semiconductors and blends change with time. The goal is to improve efficiency and stability of these devices.
4. Modeling of Nanomaterials and Nanocomposites:
We investigate the electron transport and band structure of novel electronic materials such as nanowires, nanotubes and graphene using atomistic modeling and simulation. Our work points out the delicacy of the surface properties of silicon nanowires (NWs) (below) and the dependence of electronic properties on surface composition and reconstruction. In addition, we work on developing analytical models that connect properties of single nanostrucutres to the properties of materials and devices made by using a large number of these nanostrucutures.
In our recent publication, we have used atomistic modeling to show the effectiveness of graphene for storage of hydrogen gas for hydrogen car applications.
5. Flexible Transistor and Circuit Fabrication Technology, CAD and Compact Modeling:
Deposition of electronic transistors and circuits (by inkjet printing, stamping, and vacuum deposition) on flexible substrates (e.g. plastic, paper, textile) require accurate design tools and accurate models. We have developed industry standard models for operation of transistors and circuits based on new large-area materials (amorphous and nanocrystalline silicon, organic semiconductors, and metal oxide devices). These models take into account non-ideal properties such as contact effects, body heating, non-linear mobility, mechanical flexibility and aging that play a critical role in future large-area flexible systems. The models are integrated into a industry standard CAD tool, FLEXCAD, that can be added to circuit design tools for exploring novel applications for new materials. The models and design tool has been checked with a variety of devices from different industrial and academic partners. Examples of these applications can include flexible displays, flexible digital imagers, disposable electrical sensors, health monitoring systems and rollable solar cells.
6. Biomedical Imaging Devices and Detectors:
Natural and biological materials and systems are flexible and stretchable. In line with our focus on the development of flexible electronic devices, we explore applications of new materials and microfabrication technologies for development of novel imaging devices and bio-detectors. Currently, many modalities are being used for development of new diagnosis and imaging systems that are less invasive, have higher resolution, and can monitor a targeted bio process especially in vivo. We work with medical doctors and biomedical engineers for development of low cost detectors that can be integrated on flexible substrates for endoscopy and diagnosis processes.