Asymmetric fluid-structure dynamics in nanoscale imprint lithography

thickness. Without the benefit of an accurate dispensing system, the next bestalternative was to completely fill the gap between the template and substrate.The template is raised over 20 micron above the substrate, then water is dispensedand fills the gap via capillary action.Third, the etch barrier has the same viscosity as water so that water has thesame fluid mechanic effects as the etch barrier. This can be easily seen in theincompressible Reynolds equation (see equation 2.10). The dominant fluidproperty that affects the squeeze film pressure is viscosity. The different surfacetensions of the two fluids have a negligible effect in the overall squeeze filmpressure because when the fluid completely fills the gap, the boundary effectsbecome insignificant. Furthermore, working with etch barrier to perform squeezefilm experiments also poses unknown health risks without the use of theautomated dispensing system. Therefore, it was determined that water could beused as a substitute for the etch barrier fluid.6.2.2 Data Acquisition HardwareThe data acquisition hardware consists of an 800 MHz computer with aNational Instruments AT-MIO-16XE-50 data acquisition board capable of 20Ksamples per second. The gap sensing system consists of an Ocean Optics®SQ2000 four channel UV-VIS fiber optic spectrometer containing a 25 µm slit, a600 line grating blazed at 500 nm, and 2048 pixel CCD array. The bandwidth ofthe spectrometer is from 350 to 1000 nm. With a minimum 3-millisecondintegration time, this system has a maximum spectral acquisition rate of 300 Hz.Two spectrometer channels were used to obtain film thickness results. Each fiber79