Self-Assembled Pico-Liter Droplet Microarray for Ultrasensitive Nucleic Acid Quantification

Abstract

Nucleic acid detection and quantification technologies have made remarkable progress in recent years. Among existing platforms, hybridization-based assays have the advantages of being amplification free, low instrument cost, and high throughput, but are generally less sensitive compared to sequencing and PCR assays. To bridge this performance gap, we developed a quantitative physical model for the hybridization-based assay to guide the experimental design, which leads to a pico-liter droplet environment with drastically enhanced performance and detection limit several order above any current microarray platform. The pico-liter droplet hybridization platform is further coupled with the on-chip enrichment technique to yield ultrahigh sensitivity both in terms of target concentration and copy number. Our physical model, taking into account of molecular transport, electrostatic intermolecular interactions, reaction kinetics, suggests that reducing liquid height and optimizing target concentration will maximize the hybridization efficiency, and both conditions can be satisfied in a highly parallel, self-assembled pico-liter droplet microarray that produces a detection limit as low as 570 copies and 50 aM. The pico-liter droplet array device is realized with a micropatterned superhydrophobic black silicon surface that allows enrichment of nucleic acid samples by position-defined evaporation. With on-chip enrichment and oil encapsulated pico-liter droplet arrays, we have demonstrated a record high sensitivity, wide dynamic range (6 orders of magnitude), and marked reduction of hybridization time from >10 h to <5 min in a highly repeatable fashion, benefiting from the physics-driven design and nanofeatures of the device. The design principle and technology can contribute to biomedical sensing and point-of-care clinical applications such as pathogen detection and cancer diagnosis and prognosis.

Micro‐/Nanostructured Interface for Liquid Manipulation and Its Applications

“…2) The position, geometry, amount and size of the (micro)reservoir could be precisely adjusted and organized by intelligent and flexible design of the (super)wettability patterns (Figure b). For example, the volume of microdroplet had been reported to be as low as picoliter and femtoliter, and the geometry of the (micro)reservoir can be tuned for the synthesis of materials with specific shapes, such as hydrogel particles, biofilm microcluster, metal organic framework microsheet, and nanoparticle assembly . 3) (Micro)reservoirs can be spatially close to each other because droplet coalesce is avoided, which paves the way for miniaturization and point‐of‐care application of the SPW .…”

Nano‐in‐Micro Smart Hydrogel Composite for a Rapid Sensitive Immunoassay

“…Moreover, the challenges in analysis of data from these microspheres are laborious due to the difficulties in signal quantification from randomly dispersed individual particles. Recently, to enhance the performance of bead‐based immunosensors, several techniques, including evaporation, mechanical trapping, optical trapping, and magnetic trapping, have been employed to confine the microspheres in a small region to improve the signal‐to‐noise ratio. However, the requirement of precise fluidic control or external actuators inevitably adds complexity to the assays.…”

Immobilization of Water Drops on Hydrophobic Surfaces by Contact Line Pinning at Nonlithographically Generated Polymer Microfiber Rings

“…Such chemically patterned substrates are typically produced by top‐down lithographic methods including photolithography and microcontact printing . Immobilization of water drops on hydrophobic surfaces has commonly been realized only by means of 3D topographic patterns, such as geometric poly(dimethylsiloxane) (PDMS) obstacles, hydrophobic Si pillars, and superhydrophobic black silicon indentations generated by photolithography and deep reactive ion etching …”