Real Time Imaging of Invisible Micron-Scale Monolayer Patterns on a Moving Web Using Condensation Figures

Printing of Hexadecanethiol (HDT) on thin gold substrates is the most common form of microcontact printing using self-assembled monolayers. The ability to visualize the HDT gold on a continuous moving Web, prior to subsequent steps, such as etching, is necessary to achieve any acceptable in-process quality control. In this paper, we present a real-time imaging technique for inspecting online print pattern in roll-to-roll process by condensation figures (CFs). The real-time desirable CFs are achieved through controlled consistent condensation of water vapor and a synchronous imaging process. The distribution of droplets of water acquired by fast-speed camera on an HDT-gold surface can be clustered and segmented for determining pre-etch pattern locations and geometries as well as print pattern evaluation. Our imaging system can achieve pattern resolution up to 0.7 μm, Web moving speed 3 in/s, given a low-cost camera with the frame rate up to 1500 fps. We demonstrate that the method can be promisingly used in combination with a pattern “truth table” for online quality monitoring and in-process control.