Stability Limits of Capillary Aligned Micro-Parts Subject to High Dynamics

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Capillary self-alignment shows the potential to keep small components aligned using soft liquid contact when disturbed by external forces. Whilst this concept has been promising, mostly static situations have been investigated, making it unclear how a receptor-droplet-chip (RDC) configuration behaves dynamically and where its stability limits are.

The primary aim of this research was to determine the stability limits of such a configuration and explore its failure modes. Two non-linear analytical models simulate the situation and investigate the parameters exposed to the system. These models predict the relative lateral displacement of the chip and its tilt, which can predict when failure should occur. Results from Surface Evolver, a computational software, and experimental data from a laboratory setup validate these models. A shaker induced one DOF linear accelerations, and high-speed cameras observed these tests. The validated model was then used to investigate the effects of variables such as lubricant height, chip dimensions and acceleration magnitudes.

This project gives an insight into how a chip behaves dynamically on a liquid meniscus and was the first to investigate the tilt of the component during accelerations. The key finding is a stable region showing what amount of liquid results in reaching the highest possible acceleration without failure. Secondly, the models and experiments showed that smaller liquid volumes and chip sizes increase the attainable acceleration. Chips of L = 2mm were able to be accelerated up to a = 27g without failure, parts of L = 1mm even reached an acceleration of a = 35g at which the RDC configuration remained intact. Moreover, possible eigenfrequencies were observed, and the system could re-align at specific frequencies from a tilted pose. Therefore, this research has demonstrated that, under the right conditions, capillary interfaces can be useful to transport components under high accelerations.