Self-Digitization of Sample Volumes

Abstract

This paper describes a very simple and robust microfluidic device for digitizing samples into an array of discrete volumes. The device is based on an inherent fluidic phenomenon, where an incoming aqueous sample divides itself into an array of chambers that have been primed with an immiscible phase. Self-digitization of sample volumes results from the interplay between fluidic forces, interfacial tension, channel geometry, and the final stability of the digitized samples in the chambers. Here we describe experiments and simulations that were used to characterize these parameters and the conditions under which the self-digitization process occurred. Unlike existing methods used to partition samples into array, our method is able to digitize 100% of a sample into a localized array without any loss of sample volume. The final volume of the discretized sample at each location is defined by the geometry and size of each chamber. Thus, we can form an array of samples with varying but predefined volumes. We exploited this feature to separate the crystal growth of otherwise concomitant polymorphs from a single solution. Additionally, we demonstrated the removal of the digitized samples from the chambers for downstream analysis, as well as the addition of reagents to the digitized samples. We believe this simple method will be useful in a broad range of applications where a large array of discretized samples is required, including digital PCR, single-cell analysis, and cell-based drug screening.

Stationary nanoliter droplet array with a substrate of choice for single adherent/nonadherent cell incubation and analysis

“…In addition, because the droplets in the above methods are fully sheathed by a carrier fluid, they are designed primarily for studies with suspended cells. There are methods that bypass the production and capturing under flow altogether by initially producing stationary plugs within the geometry of the device (2,(23)(24)(25). However, upon their adjustment to prolonged mammalian assays, they require multilayer fabrication, either involving high-pressure cell loading or not allowing for different substrates to be used (26,27).…”

Correlation between Sweet Spots of Glycopeptides and Polymorphism of the Matrix Crystal in MALDI Samples

“…25) ey referred to them a Form II and a Form I and showed reference Raman spectra of both forms. 26) Form II and the ordered form are the same, while there are some di erences in crystal structures by X-ray di raction analysis between Form I and the disordered form. In fact, the crystal structure of our crystal with Raman spectrum B by X-ray di raction analysis was in agreement with that for the disordered form rather than Form I (our unpublished observations).…”

“…5b) were well detected in all locations, regardless of the crystal forms because white dots exist in both the red and green regions. Because these two peptides with a B and B index 26) −4150 and −2410 commonly possess both aromatic and aliphatic amino acids, they can be considered to be hydrophobic peptides. On the other hand, the ADDKETC * FAEEGKK ion at m/z 1627.8 ( Fig.…”

Flow distribution in parallel microfluidic networks and its effect on concentration gradient

“…For instance, having a continuous flow is poorly adapted to long term observation on time scales relevant to biological experiments, which may require instead a controlled initial concentration in a closed volume. A large variety of devices already exist that maintain a concentration gradient in small chambers 19,20 or isolate a solute in small chambers using self-digitization, 21 but none of them combines isolation with concentration gradient. To remedy the situation, the gradient produced by the ladder network can be frozen within small chambers adjacent to the parallel channels, as shown in Fig.…”