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This paper proposes a new method for detecting label-free T4-DNA molecules using a Surface Plasmon Resonance (SPR1,2) technique on a gold thin film. We used a solution that dissolved T4-DNA molecules in pure water, and examined the relation between DNA concentration change and SPR angle change in the solution. As the result, it was confirmed that the SPR angle change increased with the increase of the DNA concentration change. Therefore, it was feasible to detect the DNA concentration change using the SPR technique. Further, in order to examine to detect a single DNA molecule, we calculated the area that a single DNA molecule would occupy in SPR area, and we examined to focus the beam of the SPR device at the area. However, it is difficult to focus the diameter of the spot within 500um because ofn the size of a light source and the incident angle of the light. Therefore, we tried to fabricate the SPR chip in which SPR area is narrowed that has the same effect as focusing the beam. In order to narrow the SPR area, we decreased the area of gold thin film in this chip, and also, in order to reflect a light from only the area of gold thin film, the area without a gold thin film was micro-machined to make it unevenness for the reduction of a light reflection. By the above-mentioned method, we examined the possibility to detect the label-free DNA molecule using the SPR technique.
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