Browsing by Subject "Functional polymer"
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Item ADVANCED NANOIMPRINT TECHNIQUE FOR MULTILAYER STRUCTURES AND FUNCTIONAL POLYMER APPLICATIONS(2010-07-14) Park, HyunsooThree-dimensional (3D) polymer structures are very attractive because the extra structural dimension can provide denser integration and superior performance to accomplish complex tasks. Successful fabrication of 3D multilayer microstructures in thermoplastic polymers using optimized nanoimprint lithography techniques such as layer-transfer and transfer-bonding methods are developed in this dissertation work. The capability and flexibility of the techniques developed here are expected to have deep impact on the applications of soft materials such as polymers including functional polymers in micro- and nanofabricated devices and systems. Although NIL technique is developing rapidly in recent years, there are still issues that need to be addressed for broader adoption of the nanoimprint technique. One of the problems is the residual layer that remains in the polymer pattern after nanoimprint. The conventional approach, oxygen reactive-ion-etching (RIE) process, to remove the residual layers, increases the cost and lowers the overall throughput of the nanoimprint process. More severely, it can degrade or even damage the functional polymers. In order to overcome these problems, new residual layer removal techniques need to be developed. In this dissertation, two methods are newly developed, which do not negatively affect the chemistry of the polymer materials. The techniques are suitable for all thermoplastic polymers, particularly functional polymers. Another advantage of nanoimprint is its ability to directly create functional polymers structures. This is because thermal nanoimprint only needs temperature and pressure for pattern replication, which both are benign to functional polymers. This feature combined with newly developed techniques such as transfer-bonding and residue removal techniques opens up the possibilities in nondestructive functional polymers patterning at the micro- and nanoscale for novel applications in electronics, optoelectronics, photonics and bioengineering. Finally, several applications of 3D multilayer structures fabricated by the techniques developed in this dissertation are demonstrated. The first application is a multilayer metal-dielectric-metal structure with embedded microfluidic channels. This structure can be used as an on-chip tunable filter for integrated microfluidic applications. The second application is a multilayer microfluidic channels in which each layer has a different channel size. This device can be used for particle separation and filtration based on lateral fluid flow.Item Nanoimprint Lithography for Functional Polymer Patterning(2012-02-14) Cui, DehuOrganic semiconductors have generated huge interested in recent years for low-cost and flexible electronics. Current and future device applications for semiconducting polymers include light-emitting diodes, thin-film transistors, photovoltaic cells, chemical and biological sensors, photodetectors, lasers, and memories. The performance of conjugated polymer devices depends on two major factors: the chain conformation in polymer film and the device architecture. Highly ordered chain structure usually leads to much improved performance by enhancing interchain interaction to facilitate carrier transport. The goal of this research is to improve the performance of organic devices with the nanoimprint lithography. The work begins with the controlling of polymer chain orientation in patterned nanostructures through nanoimprint mold design and process parameter manipulation, and studying the effect of chain ordering on material properties. After that, step-and-repeat thermal nanoimprint technique for large-scale continuous manufacturing of conjugated polymer nanostructures is developed. The actual chain orientation of molecular groups in polymer micro- and nanostructures patterning by nanoimprint is complicated. However, this information is crucial for intelligently controlling the electrical and photophysical properties of conjugated polymers by nanoimprint. Systematic investigation of polymer chain configuration by Raman spectroscopy is carried out to understand how nanoimprint process parameters, such as mold pattern size, temperature, and polymer molecular weight, affects polymer chain configuration. The results indicate that chain orientation in nanoimprinted polymer micro- and nanostructures is highly related to the nanoimprint temperature and the dimensions of the mold structures. The ability to create nanoscale polymer micro- and nanostructures and manipulate their internal chain conformation establishes an original experimental platform that enables studying the properties of functional polymers at the micro- and nanoscale and understanding their fundamental structure-property relationships. In addition to the impact on basic research, the techniques developed in this work are important in applied research and development. Large-area conjugated polymer micro- and nanostructures can be easily fabricated by thermal step-and-repeat nanoimprint for organic flat-panel displays, organic circuits and organic solar panels. The ability to manipulate chain orientation through nanoimprint presents a new route to fine-tune the electrical and photophysical properties of conjugated polymers, which can lead to improved performance for all organic electronics. The techniques developed here also allow for easy incorporation of other micro- and nanoscale soft functional polymers in miniaturized devices and systems for new applications in electronics, photonics, sensors and bioengineering.