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  Project abstracts can be viewed from the CD-ROM which is enclosed or the SMA website (  
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Expertise: Micro-optics, photonics, MOEMS, optical design, microfabrication and nanofabrication
Nanofabrication of DNA Micro-Array by use of Focused Ion Beam Technology
Project Advisor
Assoc Prof Ngoi Kok Ann, Bryan
Duration :
January 2003 to June 2004

Project Abstract:

Nanostructures, e.g. nano-pillars, tips array, micro-cantilever arrays, and micro-channel arrays, are very useful for biomedical use, such as cell adhesion, molecule separation and purification, and molecular detection. Particularly for arrays of nanometric sized pillars, inhibit cell attachment, and this will lead to important medical applications. The nano-pillars can be fabricated by several methods till now, such as conventional photolithography pattering and reactive ion etching transferring, and laser achromatic interferometric lithography, and then replicated by means of microcontact imprinting, embossing, etc. However, theses methods are all need two or more steps for formation of the nanostructure. Compared with them, focused ion beam direct milling (FIBM) is only one step to transfer the designed pattern into substrate. Moreover, the pillars are perpendicular with the substrate (the angle of pillar axis to substrate surface is 90¡„). The angle is determined by the crystal orientation of the substrate material during the process of dry or wet etching, and cannot be changed randomly according to practical requirements. If the angle can be changed randomly, design freedom of the nanostructure will be enlarged. It will be more helpful to cellular engineering. The FIBM is isotropic process, and limitation free of the crystal orientation. Different angles of the pillars can be obtained by use of the FIBM. Fabrication process of the FIBM investigated in detail in this project.

One-Step Nanofabrication of Diffractive Structure via Focused Ion Beam Scanning
Project Advisor
Assoc Prof Ngoi Kok Ann, Bryan
Duration :
September 2003 to December 2004

Project Abstract:

A new fabrication method for diffractive structures, we call it quasi-direct writing, was illustrated in this letter. The diffractive structures can be generated by changing pixel space of cross scan direction (overlap is zero) and keeping the other space along scan direction constant with normal overlap of 50-60% during scanning substrate surface by use of focused ion beam (FIB). It is a method of computer program free. The diffractive structures with different period and depth can be derived by controlling the parameters of pixel spaces, beam current, ion incident angle, and scan time/ion dose. It has no material selectivity, and can be used for materials of metal, insulator, and semiconductor.

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