Development of a novel mechanical micro-engraving method for the high-aspect-ratio microstructures of an advanced window system

A transparent polymer film with embedded micro mirrors is developed, and it can be attached to a window glass pane for daylighting, improving visual comfort and reducing cooling load in buildings by redirecting sunlight. Despite existing cutting-edge techniques, the fabrication of large-area, linear micro structured surfaces combining high aspect ratio, curve sidewalls and a controlled shape remains challenging. In order to solve the problem, a novel mechanical scanning engraving method using blades with micro-teeth of desired patterns on soft substrates is developed. The usage of a blade enables the combination of high aspect ratio with almost any closed profile. Such blades can be obtained in a large variety of shapes using UV-LIGA technology which combines photolithography and electroforming. Master molds were prepared and the following steps of micro UV-imprinting from the master molds are also introduced. The present work confirms the feasibility of the fabrication for parabolic sidewall microstructures of aspect ratio of 3.8 and 6.7 with good controlled shapes. With a scanning speed of 0.15 m/min, the method is proven to be efficient and appropriate for large-area microstructured fabrication.