A chemical approach for the regulation of oil (under water) and water (in air) wettability. The super-wetting properties are highly durable at harsh physical/chemical settings.

Materials with extremes of water wettability are of potential interest in various fundamental and applied contexts. However, often, poor chemical and physical durabitity of conventional thin special wettable materials stands in the way of prospective applications of this property at practical settings. A chemically “reactive” polymeric gel material is introduced here, and advantage is taken of the robust and facile 1,4-Michael addition reaction between acrylate and primary amine groups to develop a chemically cross-linked and bulk (including interior and surface) super­hydro­phobic material. A mixture of dipenta­erythritol penta­acrylate and branched poly­(ethyl­en­imine) (BPEI) can rapidly form a self-standing gel network. On removal of solvent molecules, the synthesized gel network provides a highly porous and reactive polymeric matrix that can be further modified with a variety of small molecules to tailor the liquid water wettability on the synthesized material. This approach provides a facile and rapid process to fabricate a bulk (internally) super­hydro­phobic material of arbitrary size that can take complex shapes. This property of the material remains intact even after various standard chemical and physical insults. This synthetic strategy could be useful in developing advanced and multifunctional materials to further broadening the applications of this anti-wetting property, including oil/water separation, self-cleaning, sustaining and slow drug release, etc.

Rapid, robust virus detection techniques with ultrahigh sensitivity and selectivity are required for the outbreak of the pandemic coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). Here, we report that the femtomolar concentrations of single-stranded ribonucleic acid (ssRNA) of SARS-CoV-2 trigger ordering transitions in liquid crystal (LC) films decorated with cationic surfactant and complementary 15-mer single-stranded deoxyribonucleic acid (ssDNA) probe. More importantly, the sensitivity of the LC to the severe acute respiratory syndrome (SARS) ssRNA, with a 3 base pair-mismatch compared to the SARS-CoV-2 ssRNA, is measured to decrease by seven orders of magnitude, suggesting that the LC ordering transitions depend strongly on the targeted oligonucleotide sequence. Finally, we design a LC-based diagnostic kit and a smartphone-based application (App) to enable automatic detection of SARS-CoV-2 ssRNA, which could be used for reliable self-test of SARS-CoV-2 at home without the need for complex equipment or procedures.

A facile and robust Michael addition reaction is strategically exploited here, to develop a highly stretchable (150% deformation) superhydrophobic material. This material strongly repels aqueous phase both in air and under oil and with impeccable physical/chemical durability, and is appropriate for rapid separation of both heavy and light oils from complex aqueous phases with above 99% efficiency.

The ability to control both the mobility and chemical compositions of microliter-scale aqueous droplets is an essential prerequisite for next-generation open surface microfluidics. Independently manipulating the chemical compositions of aqueous droplets without altering their mobility, however, remains challenging. In this work, we address this challenge by designing a class of open surface microfluidic platforms based on thermotropic liquid crystals (LCs). We demonstrate, both experimentally and theoretically, that the unique positional and orient ational order of LC molecules intrinsically decouple cargo release functionality from droplet mobility via selective phase transitions. Furthermore, we build sodium sulfide-loaded LC surfaces that can efficiently precipitate heavy metal ions in sliding water droplets to final concentration less than 1 part per million for more than 500 cycles without causing droplets to become pinned. Overall, our results reveal that LC surfaces offer unique possibilities for the design of novel open surface fluidic systems with orthogonal functionalities.