Oil-Triggered and Template-Confined Dewetting for Facile and Low-Loss Sample Digitization

Abstract

This paper proposes a simple and robust method for spontaneously digitizing aqueous samples into a high-density microwell array. The method is based on an oil-triggered template-confined dewetting phenomenon. To realize the dewetting-induced sample digitization, an aqueous sample is first infused into a networked microwell array (NMA) through a pre-degassing-based self-pumping mechanism, and an immiscible oil phase is then applied over the surface of NMA chip to induce the templated dewetting. Due to periodic interfacial tension heterogeneity, such dewetting ruptures the sample at the thinnest parts (i.e., connection channels) and spontaneously splits the sample into droplets in individual microwells. Without requiring any complex pumping or valving systems, this method can discretize a sample into tens of thousands of addressable droplets in a matter of minutes with nearly 98% usage. To demonstrate the utility and universality of this self-digitization method, we exploited it to discretize samples into 40 233 wells for a digital PCR assay, the digital quantification of bacteria, the self-assembly of spherical colloidal photonic crystals, and the spherical crystallization of drugs. We believe this facile technique will provide a substantial benefit to many compartmentalized assays or syntheses where it is necessary to partition samples into a large number of small individual volumes.

Controlled Rehydration of Dried Reagents for Robust Multiplex Digital PCR

“…In each array, all microwells are arrayed in a honeycomb pattern, and individual microwells are connected to the circumferential six neighboring microwells or a peripheral main channel (50 μm in width and 50 μm in depth) by narrow and shallow microchannels (8 μm in width and 20 μm in depth). Such a networked microwell array allows a higher density of microwells and a faster filling of all the microwells with minimal sample loss …”

“…The microwell layer contains eight arrays, each with 21,058 microwells (40 μm Such a networked microwell array allows a higher density of microwells and a faster filling of all the microwells with minimal sample loss. 24 2.2. Device Fabrication.…”

“…The multiplex dPCR chip was fabricated using a multilayer soft lithography as described previously. 24 Briefly, two separate masters were fabricated using standard lithographic procedures to create the cover and microwell layers, respectively. A two-level master was prepared from SU-8 3010 and 3050 (MicroChem Corp., Newton, MA) on a 4 in.…”

“…Owing to the high wettability, the pipetted oil spontaneously covered the upper surface of the microwell layer. Under the action of Laplace pressure, oil-triggered and template-guided dewetting occurred, 24 resulting in the isolation of all primed microwells and thus self-digitization of the aqueous sample. In addition to sample digitization, this oil covering can also inhibit possible contamination and water evaporation during peeling off.…”

Microwell Confined Electro‐Coalescence for Rapid Formation of High‐Throughput Droplet Array

“…The 5 cSt silicone oil containing 0.5 wt% KF6017 was used as the continuous phase to prepare the emulsion. The droplet arrays formed on the ECDA chips were placed in a shaking incubator at 37 °C for 4 h. [51,52] The obtained array chip was then imaged using an inverted fluorescence microscopy to observe and count the positive droplets. Movie S3, Supporting Information shows the incubated bacteria in droplet, and the fluorescence images are shown in Figure 5A.…”