Fluidic shaping and in-situ measurement of liquid lenses in microgravity.

In the absence of gravity, surface tension dominates over the behavior of liquids. While this often poses a challenge in adapting Earth-based technologies to space, it can also provide an opportunity for novel technologies that utilize its advantages. In particular, surface tension drives a liquid body to a constant-mean-curvature shape with extremely smooth surfaces, properties which are highly beneficial for optical components. We here present the design, implementation and analysis of parabolic flight experiments demonstrating the creation and in-situ measurement of optical lenses made entirely by shaping liquids in microgravity. We provide details of the two experimental systems designed to inject the precise amount of liquid within the short microgravity timeframe provided in a parabolic flight, while also measuring the resulting lens' characteristics in real-time using both resolution target-imaging and Shack-Hartmann wavefront sensing. We successfully created more than 20 liquid lenses during the flights. We also present video recordings of the process, from the lenses' creation during microgravity and up until their collapse upon return to gravity. The work thus demonstrates the feasibility of creating and utilizing liquid-based optics in space.

Current monitoring in a microchannel with repeated constrictions for accurate detection of sample location in isotachophoresis.

We present a new method for accurate detection of sample location in peak mode isotachophoresis (ITP). The technique is based on the design of a microchannel with multiple constrictions and on detecting the passage of the ITP interface through these constrictions. We achieve this by monitoring the electric current across the channel, which exhibits sharp decreases as the ITP interface moves more rapidly through the higher current density constrictions. We show that cross-correlation between the electric current signal and a predefined step function is an effective method for detecting changes in the slope of the electric current curve in real-time and is robust to changes in the composition of the buffers. We demonstrate the use of the technique to deliver sample to a designated location in the channel with an accuracy as low as 50 µm. Importantly, the method does not require the use of any optics and thus can be used to monitor the location of unlabeled species for application in a variety of ITP assays.