Superhydrophobic metallic materials have drawn broad research interest because of promising applications in various fields. The mechanical stability of superhydrophobic surfaces is currently a major concern limiting their practical applications. Herein, we developed a simple method to fabricate robust superhydrophobic surfaces on stainless steel via direct ultrafast laser microprocessing. Of note is that the fabricated superhydrophobic surfaces can withstand mechanical abrasion against an 800 grit SiC sandpaper for 2.3 m at an applied pressure of 5.5 kPa without losing superhydrophobicity. It is proposed that the robust superhydrophobicity may be attributable to the formation of unique hierarchical micro-/nanostructures and a nonpolar carbon layer on the surface. The hierarchical structures are composed of laser-created micropillars and ablation-induced nanoparticles. The fabricated surfaces exhibit good thermal stability and still show superhydrophobicity after thermal treatment at 100 °C for 120 min, which is related to the inorganic nature of metallic materials. An excellent anti-icing property is achieved on the fabricated surfaces with the water droplets on it retaining the liquid state for over 500 min at −8.5 ± 0.5 °C, which benefits from the obtained superhydrophobicity, based on classic nucleation theory and the heat transfer between the rough solid surface and water droplet. We envision that the presented method provides a facile and effective route to fabricate large-area superhydrophobic surfaces with robust mechanical stability and excellent anti-icing property.

A paper-based microfluidic device with upconversion fluorescence assay (named as UC-μPAD) is proposed. The device is fabricated on a normal office printing sheet with a simple plotting method. Upconversion phosphors (UCPs) tagged with specific probes are spotted to the test zones on the μPAD, followed by the introduction of assay targets. Upconversion fluorescence measurements are directly conducted on the test zones after the completion of the probe-to-target reactions, without any post-treatments. The UC-μPAD features very easy fabrication and operation, simple and fast detection, low cost, and high sensitivity. UC-μPAD is a promising prospect for a clinical point-of-care test.

We report the first portable upconversion nanoparticles (UCNPs)-based paper device for road-side field testing of cocaine. Upon the recognition of cocaine by two pieces of rationally designed aptamer fragments, the luminescence of UCNPs immobilized on the paper is quenched by Au nanoparticles (AuNPs), which indicates the cocaine concentration. This device can give quantitative results in a short time with high sensitivity using only a smartphone as the apparatus. Moreover, this device is applicable in human saliva samples, and it also can be used to monitor the cocaine content change in blood samples. The results of this work demonstrate the prospect of developing UCNPs-based paper devices for field testing of drug abuse.

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