Double mold imprinting of micro fluidic device with ultra-thin PDMS window for in-vitro X-ray microscopy observation

We developed a double mold imprinting technique to fabricate micro-fluidic device with ultra-thin polydimethylsiloxane (PDMS) window for in-vitro X-ray microscopy. An X-ray having a specific wavelength from 2.33 nm to 4.23 nm, the so called water window region defined between the absorption edge of oxygen and the K-edge of nitrogen, has a large absorption contrast for bio-molecules against water. Therefore, the X-ray microscope imaging in Takano et al. (1995) with this wavelength is expected to reveal detailed in-vitro structure of biomaterials. Even though large contrast is gained, a specimen should be less than a few microns thick, and the biomaterial dispersed into the water should be held within this thin region. To create a specimen holder for in-vitro X-ray microscopy, we developed a micro fluidic device equipped with a 2-μm thick PDMS window based on double mold imprinting technique in Kong et al. (2004).