Single-Droplet Multiplex Bioassay on a Robust and Stretchable Extreme Wetting Substrate through Vacuum-Based Droplet Manipulation

Abstract

Herein, a droplet manipulation system with a superamphiphobic (SPO)-superamphiphilic (SPI) patterned polydimethylsiloxane (PDMS) substrate is developed for a multiplex bioassay from single-droplet samples. The SPO substrate is fabricated by sequential spraying of adhesive and fluorinated silica nanoparticles onto a PDMS substrate. It is subsequently subjected to oxygen plasma with a patterned mask to form SPI patterns. The SPO layer exhibits extreme liquid repellency with a high contact angle (>150°) toward low surface tension and viscous biofluidic droplets (e.g., ethylene glycol, blood, dimethyl sulfoxide, and alginate hydrogel). In contrast, the SPI exhibits liquid adhesion with a near zero contact angle. Using the droplet manipulation system, various liquid droplets can be precisely manipulated and dispensed onto the predefined SPI patterns on the SPO PDMS substrate. This system enables a multiplex colorimetric bioassay, capable of detecting multiple analytes, including glucose, uric acid, and lactate, from a single sample droplet. In addition, the detection of glucose concentrations in a plasma droplet of diabetic and healthy mice are performed to demonstrate the feasibility of the proposed system for efficient clinical diagnostic applications.

Bioinspired Superwettability Micro/Nanoarchitectures: Fabrications and Applications

“…These properties derived from superwettability have been harnessed in many applications including photovoltaics, organic light‐emitting diodes (OLEDs), cell capture, and lab‐on‐chip devices . Here, we limit our discussion to the process made over the past 3 years in emerging applications of topological textured surfaces including optoelectronics, droplet manipulation, microreactor biochemical assays, and medical coatings …”

“…On such a surface, a suspended solution droplet evaporates, and the solute gradually becomes concentrated with no loss due to the nonwetting property of the surface . After evaporation, the solution drop collapses and the molecules precipitate on the micro/nanostructures of the superhydrophobic surface for further detection . The combination of superhydrophobic surfaces and nanoplasmonic sensors ( Figure a–h) enables the single‐molecule detection of chemicals and biomolecules at femtomolar (10 −15 mol L −1 ) or attomolar (10 −18 mol L −1 ) levels (Figure i,j).…”

“…Superhydrophobic/superhydrophilic patterned surface ( Figure a) can be used to dispense numerous aqueous microdroplets as arrays precisely (Figure b,c) . By passively smearing an aqueous solution on the patterned superwettable surface (Figure d), microdroplets are dispensed in the superhydrophilic areas without wetting the superhydrophobic regions . The volume, position, and geometry of the deposited microdroplets can be controlled by changing the wettability patterns (Figure e,f).…”

“…The volume, position, and geometry of the deposited microdroplets can be controlled by changing the wettability patterns (Figure e,f). The solute in aqueous microdroplet arrays can be further enriched by condensation, while these droplets are pinned in the hydrophilic regions . As such, high‐throughput droplet‐based chemical sensing of heavy metal ions, bacteria assays, biochemical assays, biocatalytic reactions, and multiplex bioassays can be performed …”

Micro‐/Nanostructured Interface for Liquid Manipulation and Its Applications

“…Until now, SPW had been extensively explored as an effective high‐throughput platform for bioassay and biosensing . For example, Wang group developed SPW for various biosensing, such as sensitive nucleic acid detection based on condensing‐enrichment effect, microgravity biosensing and electrochemical detection toward cancer biomarkers .…”