The Effects Of Blast Lag In Abrasive Jet Machined Micro-Channel Intersections

Abrasive jet micro-machining (AJM) uses compressed air carrying abrasive solid particles to micro-machine a variety of features into surfaces. If the features are smaller than a few mm, then a patterned erosion-resistant mask is used to protect the substrate material, leaving exposed areas to define the features. Previous investigations have revealed a ‘blast lag’ phenomenon in which, for the same dose of abrasive particles, the etched depth of micro-channels and holes tends to decrease as the features become narrower. Blast lag occurs when using AJM on brittle substrates because of the natural tendency to rapidly form a V-shaped cross-sectional profile which inhibits abrasive particle strikes on the narrow vertex at the feature centerline. In this thesis, for the first time, the blast lag phenomenon is studied when using AJM to machine a network of microfluidic channels. It is found that, in some cases, differences in blast lag occurring at channel intersections and within the channels themselves, can lead to channel networks of non-uniform depth. A previously developed surface evolution model is used to predict the onset of blast lag in the channels and intersections, and thus explain these differences. Finally, methods to eliminate the differences are discussed.