A rotating mask system for sculpting of three-dimensional features using abrasive jet micro-machining

Channels with non-conventional shaped cross sections have applications especially in microfluidics, where flow and heat transfer characteristics may depend on shape. Most microfabrication technologies capable of sculpting desired micro-channel shapes are limited in the range of shapes they can produce. Abrasive jet micromachining (AJM) uses a jet of impacting abrasive particles to mechanically etch the target surface. Its directional etch capability makes it well suited for the sculpting of a wide variety of micro-features with three-dimensional (3D) topographies. Elastomeric masks have in the past been used to define complex patterns in AJM applications. Traditionally, such masks have been applied directly to the target, but this only allows the AJM of shallow features without any control over their cross-sectional shape. This paper presents a new technique that allows the instantaneous AJM erosive footprint size and shape to be controlled using a novel rotating mask apparatus (RMA). Models for predicting the required rotating mask pattern required to create a desired footprint are also presented. The models were experimentally verified for symmetric and asymmetric W-shaped, trapezoidal and wedge shaped footprints. The benefits of the RMA include: (i) the ability to generate virtually any footprint, including those that mimic moving a source (e.g. nozzle) or multiple sources of various sizes instantly from one location to another; (ii) improved mask longevity; and (iii) use of traverses in a straight line, rather adjacent traverses, in order to sculpt desired 3D feature shapes.