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This work yields an inexpensive and fast process to replace the current standard of microscale periodic structure fabrication.
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            Two-Dimensional Crystal Fabrication

INTRODUCTION

 
   My name is Pisist (PAO)  KUMNORKAEW, a Ph.D candidate at Lehigh University.  I build this website to share my experiences with all visitors. I would like to thank to Prof. James F. Gilchrist for his advice.



                                                     BACKGROUND
       
            Controlled colloidal and/or nanoparticle deposition on substrates has impact on fields ranging from catalysis, photonics, lithography ,ceramics, biocompatible surfaces, and sensors.  Many applications are highly dependent on the microstructure, e.g. surface density, crystallinity, and orientation of these modified surfaces.  My research yields an inexpensive and fast process to replace the current standard techniques; whereas the fabrication of a square inch of microarrays containing billions of lenses would have taken hours or days with current processes, my fabrication technique takes just minutes. Check out Laboratory supplies and Experiment technique  HERE!!...




MONOLAYER DEPOSITION


Rather than using traditional lithography technique, we form microarrays through convective self assembly of 0.5 and 1 µm colloidal particles in two dimensional (2D) crystals. In these experiments, a cover glass slide substrate is placed horizontally on a stage. It’s movement is driven by a shaft drive while another glass slide used as deposition blade is angled into the substrate at a desired angle (25-80o). The deposition speed ranges up to 0.2 mm/sec. An inch square 2D crystal is formed with  20% silica suspension in less than 1 0 minutes. The snapshot of hexagonal closed- pack and square pack structure were taken using our confocal microscope. More
 

                                 Soft Lithograpy via 2D Crystal


On the top GaN layer of an LED (Quantum well)or any substrate, soft-lithography techniques create an inverted structure (concave micro lens) on the device. In addition, this pattern can be used as a template for subsequent depositions of PS and silica. Here the inversed structure of hexagonal and sqaure pack structure are shown. Tip size is range from 20-200 nm. Great for nanotechnology!!! ...More

 

                               

    Self Assembly under Convective Evaporation

 

 

              Our high speed confocal microscope and image analysis technique revealed an interesting flow phenomena under rapid convective deposition. Here you see regions of  monolayer crystal growth (right), thinfilm (middle), and reversed flow (left). A mathematical model described the flow is under development.  Click Here to see other interesting phenomena. 



2D Crystal Monolayer on a Flat Substrate

        







            Direct Fabrication of 2D crystal using Binary Colloid


 


Silica/polystyrene (PS) microlens arrays are fabricated by a single deposition of a binary suspension of micron-sized silica and nanoscale PS rather than through layer–by-layer deposition. Nanoscale polystyrene helps increase colloid stability in solution. ...More

 


 

 

                        Reversed Structure via HF Etching


A reversed structure of resolidified polystyrene was created by selectively remove silica particle using hydrofluric acid. The shape of concave structure is controlled by amount of polystyrene deposited on silica monolayer..Click Here for more pictures.
 
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