Acoustofluidic one-step production of plasmonic Ag nanoparticles for portable paper-based ultrasensitive SERS detection of bactericides.

SERS measurements for monitoring bactericides in dairy products are highly desired for food safety problems. However, the complicated preparation process of SERS substrates greatly impedes the promotion of SERS. Here, we propose acoustofluidic one-step synthesis of Ag nanoparticles on paper substrates for SERS detection. Our method is economical, fast, simple, and eco-friendly. We adopted laser cutting to cut out appropriate paper shapes, and aldehydes were simultaneously produced at the cutting edge in the pyrolysis of cellulose by laser which were leveraged as the reducing reagent. In the synthesis, only 5 µL of Ag precursor was added to complete the reaction, and no reducing agent was used. Our recently developed acoustofluidic device was employed to intensely mix Ag+ ions and aldehydes and spread the reduced Ag nanoparticles over the substrate. The SERS substrate was fabricated in 1 step and 3 min. The standard R6G solution measurement demonstrated the excellent signal and prominent uniformity of the fabricated SERS substrates. SERS detection of the safe concentration of three bactericides, including tetracycline hydrochloride, thiabendazole, and malachite green, from food samples can be achieved using fabricated substrates. We take the least cost, time, reagents, and steps to fabricate the SERS substrate with satisfying performance. Our work has an extraodinary meaning for the green preparation and large-scale application of SERS.

Micro-pin-finned Surfaces with Fractal Treelike Hydrophilic Networks for Flow Boiling Enhancement.

Due to its outstanding heat transfer performance, flow boiling has a wide range of applications in many fields, especially for cooling of electronic devices. Previous studies have shown that the liquid replenishment on the downstream of the heating surface is the critical restriction of the increase of the critical heat flux (CHF). In this work, we designed a series of heterogeneous surfaces with fractal treelike hydrophilic networks for flow boiling enhancement. The micro-pin-finned surface structures are expected to increase the CHF and reduce the superheat by its high wickability. Moreover, by virtue of the efficient transport capacity of treelike networks, the fractal hydrophilic paths are designed to serve as the liquid delivery channels for the liquid replenishment on the downstream of the heating surface. The heterogeneous surfaces improve the comprehensive boiling heat transfer performance, especially the CHF, which is 82.2% higher than that of the smooth surface and 5.4% higher than the surface homogeneously covered by the microstructure with twice of the extended surface area. This work provides reference for the design of heterogeneous surfaces with both smooth and structured parts to increase the flow boiling CHF to some extent.

Convenient and large-scale fabrication of cost-effective superhydrophobic aluminum alloy surface with excellent reparability.

Superhydrophobic surfaces are widely used in industry and daily life, yet their practical application is limited by their complicated preparation process, high cost, and poor repairability. We propose a low-cost, facile process for preparing superhydrophobic surfaces to address this limitation. Through a simple three-step spraying process, the rough structure was first constructed on the aluminum alloy, and upon modification by modifier, the superhydrophobic aluminum alloy surface was successfully prepared. The effect of the process parameters on wettability was experimentally studied. The results showed that this method can obtain superhydrophobic surfaces with a contact angle of 156.2° and contact angle hysteresis of 7.4° by simply adjusting the etching time and modifier concentration. In addition, it was found that the prepared surface can keep the superhydrophobic property unchanged at 180 °C, showing good thermal stability. When immersed in acetic acid and sodium hydroxide solution, the prepared surface can maintain its superhydrophobicity for about 2 days, showing good chemical stability. Besides, the surface has excellent repairability and can compensate for the short-life defects caused by poor friction resistance. This superhydrophobic surface with a simple preparation process, low cost, and excellent repairable characteristics also has excellent self-cleaning, antifogging, and antifrosting applications.