Superhydrophilic/Superhydrophobic Droplet Microarrays of Low Surface Tension Biofluids for Nucleic Acid Detection

Abstract

Abstract Superhydrophilic/superhydrophobic patterned surfaces can be used to create droplet microarrays. A specific challenge with the liquids needed for various biomedical applications, as compared to pure water, is their lower surface tension and potential for contaminating the surfaces through adsorption. Here, a method is shown to create biofluid droplet microarrays using discontinuous dewetting of pure water, an oil protective layer, and finally biofluid exchange with the water droplet array. With this method, a droplet array of a viscous nucleic acid amplification solution can be formed with a low surface tension of 34 mN m−1 and a contact angle of only 76° with the used hydrophobic coating. This droplet array is applied for nucleic acid detection of SARS‐CoV‐2 virus using strand invasion‐based amplification (SIBA) technology. It is shown that by using an array of 10 000 droplets of 50 µm diameter the limit of detection is 1 RNA copy µL−1. The results demonstrate that SIBA on droplet microarrays may be a quantitative technology.

Keywords

• biofluids
• black silicon
• digital nucleic acid amplification
• microfluidics
• wettability patterning