Papers by Author: Seung Seob Lee

Abstract: We present a novel microcantilever device with nano-interdigitated electrodes (nano-IDEs) and selective functionalization of nano-IDEs for biosensing applications. The nano-IDEs play a role in precisely addressing capture molecules to a specific region on a microcantilever. This leads to a detectable surface stress due to the binding of target molecules. 70~500 nm-wide gold (Au) nano- IDEs are fabricated on a low-stress SiNx microcantilever with dimensions of 100~600 μm in length, and 15~60 μm in width, with a 0.5 μm thickness using electron beam lithography and bulk micromachining. 32~96 nm-thick streptavidin is selectively deposited on one side of nano-IDEs using cyclic voltammetry at a scan rate of 0.1 V/s with a range of -0.2~0.7 V during 1~5 cycles. The selective deposition of streptavidin is confirmed by fluorescence microscopy and atomic force microscopy (AFM).

Abstract: A novel micro cell incubator is described in this paper. pH of animal cell culture media must be tightly controlled, and this is accomplished by supplying defined concentration of carbon dioxide. In order to fabricate a small self-contained carbon dioxide supply unit, we adopted chemical production of carbon dioxide rather than compressed storage of the gas which requires huge tank. Carbon dioxide can be chemically produced by pyrolysis of sodium bicarbonate. The produced gas passes through a thin polymer membrane which is known to admit diffusion of gases. Liquid media separated from gas area by polymer membrane can uptake the gas, then. This micro cell incubator would be a suitable model for the development of portable and arrayed cell chips.

Abstract: We design and fabricate a novel flexural plate wave (FPW) accelerometer which has wide working range and improved sensitivity. A bridge as well as a rectangular diaphragm with a proof mass has been considered for a wave propagation medium to enhance the performance. The performance improvement is also verified with the bridge structure and the existence of the proof mass in the simulation results.

Abstract: In order to measure the mechanical properties of gold films on silicon substrate, two types of specimens, i.e., bridged films and circular membranes, are manufactured. Using a wedge tip, the bridged gold films are indented so that the films are pushed off, which is called as V-peel test. The load-deflection curves obtained by the V-peel test are analyzed with the concept of geometrically nonlinear beam by using the minimum potential energy theory together with Ritz method. Thus, Young’s modulus and residual stress of the bridged gold films are obtained. Blister test is also conducted to measure the Young’s modulus and residual stress of a circular gold membrane, of which deformation is measured by Twyman-Green interferometer. By gradually increasing the external pressure applied on the membrane, the interfacial fracture toughness between the gold membrane and silicon substrate is measured based on the concepts of interfacial fracture mechanics.