- Current Research 1: Nanomanufacturing and Composites for Plasmonic Metamaterials
A metamaterial is a material engineered to have a property that is not found in nature. They are made from assemblies of multiple elements fashioned from composite materials such as metals or plastics. The materials are usually arranged in repeating patterns, at scales that are smaller than the wavelengths of the phenomena they influence. Metamaterials derive their properties not from the properties of the base materials, but from their newly designed structures. Their precise shape, geometry, size, orientation and arrangement gives them their smart properties capable of manipulating electromagnetic waves: by blocking, absorbing, enhancing, or bending waves, to achieve benefits that go beyond what is possible with conventional materials. (Wikipedia)
In CML, we create metamaterials using scalable nanomanufacturing technologies, such as nanoimprint lithography and nanotransfer printing, to apply them in various applications including the single bio-molecule detection and the infrared polarimetric sensing/imaging.
Composite is defined as a heterogeneous material system consisting of reinforcing materials, which are in forms of fibers, whiskers, platelets, and particulates, dispersed in continuous matrix materials. Interactions between the nanoscale inclusions and matrix materials can create extraordinary functionalities, such as electrical conductivity, electromagnetic shielding, magnetoresistance, that the individual constituents could not achieve. ‘Metacomposite’ is a new class of the multifunctional composites that can tune the electromagnetic properties. We study the multiphysics interactions within the composite material system to take advantages of the un-usual properties to realize novel electromagnetic devices.
- Current Research 2: Additive Manufacturing for Printed Electronics and Functionally Graded Materials
Additive manufacturing (AM) is a process that creates parts by continuously adding material layer by layer. This technique has been utilized to create complex structures, such as internal hierarchal patterns, which are impossible to create with other conventional manufacturing methods. AM has been used in several fields such as dental, medical, aerospace, electronics, and microfluidics to produce unique devices.
We utilize the printing capability to create electronics on flexible substrates. In high throughput roll-to-roll (R2R) and sheet-to-sheet (S2S) manufacturing environment, direct print technologies (gravure, flexography, and ink-jet) provide lower cost and larger printing area. The use of metallic nanoinks, where metal nanoparticles are dispersed in printable carriers, has attracted great interest because of inherently higher electric conductivity and mechanical durability. However, unlike organic-based electronic materials, the metallic nanoinks require sintering process in order to form conductive films. We studied a novel photonic sintering process using Xe-flash lamp. The advantages of the Xe-flash photonics sintering are: (1) Little impact to polymer substrate – Unlike the conventional furnace whose temperature is detrimental to the substrate, room temperature sintering is achieved through selective heating of nanoparticles over the polymeric substrates; (2) Scalable manufacturing – the photonic process can be applied on much larger areas at once in comparison to laser-based spot sintering technique.
As the AM technology matures, the number of printable materials has greatly increased. Research into new materials and the efects of complex structural arrangements has increased tremendously both from industry and academia looking for novel applications to this technology. AM technologies are capable of locally tuning material properties to generate Functionally Graded Materials (FGM). Artificially engineered FGMs have been applied to create aerospace structural materials, lightweight concrete structures, and bone mimicking implants. However, the capability of conducting meaningful computer simulations for FGMs is limited mainly due to the lack of information regarding the material properties and appropriate material models. In our recent study, we developed mechanical models of the printed materials and validated the model-based computational analysis by comparing with physical tests.
We currently wants all levels of research assistants (undergraduate, graduate, and postdoc) in the topics.
- Carbon Fiber Reinforced Polymer (CFRP) Composites
- CFRP fabrication with functional nanomaterials (e.g. carbon nanotubes)
- Testing mechanical strength
- Machining of CFRP
- Scalable manufacturing of micro-, nano-scale hierarchical 3-dimensional structures
- Developing a manufacturing equipment
- Study the process influence on the 3-D structure with nanoscale characterization tools
- Mechanical simulation of the manufacturing process