Rectification of Mobile Leidenfrost Droplets by Planar Ratchets.

The self-transportation of mobile Leidenfrost droplets with well-defined direction and velocity on millimetric ratchets is one of the most representative and spectacular phenomena in droplet dynamics. Despite extensive progress in the ability to control the spatiotemporal propagation of droplets, it remains elusive how the individual ratchet units, as well as the interactions within their arrays, are translated into the collective droplet dynamics. Here, simple planar ratchets characterized by uniform height normal to the surface are designed. It is revealed that on planar ratchets, the transport dynamics of Leidenfrost droplets is dependent not only on individual units, but also on the elegant coordination within their arrays dictated by their topography. The design of planar ratchets enriches the fundamental understanding of how the surface topography is translated into dynamic and collective droplet transport behaviors, and also imparts higher applicability in microelectromechanical system based fluidic devices.

Liquid metal droplets bouncing higher on thicker water layer.

Liquid metal (LM) has gained increasing attention for a wide range of applications, such as flexible electronics, soft robots, and chip cooling devices, owing to its low melting temperature, good flexibility, and high electrical and thermal conductivity. In ambient conditions, LM is susceptible to the coverage of a thin oxide layer, resulting in unwanted adhesion with underlying substrates that undercuts its originally high mobility. Here, we discover an unusual phenomenon characterized by the complete rebound of LM droplets from the water layer with negligible adhesion. More counterintuitively, the restitution coefficient, defined as the ratio between the droplet velocities after and before impact, increases with water layer thickness. We reveal that the complete rebound of LM droplets originates from the trapping of a thinly low-viscosity water lubrication film that prevents droplet-solid contact with low viscous dissipation, and the restitution coefficient is modulated by the negative capillary pressure in the lubrication film as a result of the spontaneous spreading of water on the LM droplet. Our findings advance the fundamental understanding of complex fluids' droplet dynamics and provide insights for fluid control.

Angiotensin-converting enzyme - human amniotic mesenchymal stem cells improve pulmonary vascular remodeling in rats with pulmonary hypertension by promoting angiogenesis and counteracting inflammation.

OBJECTIVES: Human Amniotic Mesenchymal Stem Cells (hAMSCs) have strong multidirectional differentiation ability. Studies have found that transfection of target genes into target cells by lentivirus can enhance the differentiation potential of the cells. Angiotensin-Converting Enzyme 2 (ACE2) was found to improve vascular remodeling. Research is lacking on ACE2-hAMSCs. Therefore, this study aimed to investigate the ability to improve pulmonary arterial hypertension using ACE2-hAMSCs. METHODS: Lentiviruses overexpressing ACE2 were mixed with hAMSCs. Then, ACE2-hAMSCs and hAMSCs with good growth in logarithmic growth phase were collected. We detected their migration and angiogenesis. RT-qPCR technology was used to detect the expression levels of genes related to angiogenesis, and inflammation in the two cell lines, and western-blotting was used to detect the expression levels of ACE2. As an animal study, 21 rats were randomly divided into four different groups. Right heart hypertrophy, pulmonary angiogenesis, and serum inflammatory factors were measured before dissection. H&E staining was used to observe the inflammatory infiltration of lung tissues. RESULTS: The migration and angiogenesis of ACE2-hAMSCs were strongerthan that of hAMSCs alone. The expressions of genes in ACE2-hAMSCs were higher, and the expression of ACE2 protein in ACE2-hAMSCs was less. H&E staining showed that the inflammatory infilration of lung tissue in ACE2-hAMSCs groups was significantly improved. In addition, the ACE2-hAMSCs group had stronger pro-angiogenesis and anti-inflammatory effects. CONCLUSION: These results suggest that ACE2-hAMSCs can repair pulmonary vascular endothelial cell injury caused by pulmonary hypertension by promoting angiogenesis and anti-inflammatory ability. This shows that ACE2-hAMSCs have stronger ability to improve pulmonary vascular remodeling than hAMSCs alone.

Distinct soil bacterial patterns along narrow and broad elevational gradients in the grassland of Mt. Tianshan, China.

Bacteria are essential regulators of soil biogeochemical cycles. While several studies of bacterial elevational patterns have been performed in recent years, the drivers of these patterns remain incompletely understood. To clarify bacterial distribution patterns and diversity across narrow- and broad-scale elevational gradients, we collected soil samples from 22 sites in the grasslands of Mt. Tianshan in China along three elevational transects and the overall elevation transect: (1) 6 sites at elevations of 1047-1587 m, (2) 8 sites at 876-3070 m, and (3) 8 sites at 1602-2110 m. The bacterial community diversity across the overall elevation transects exhibited a hump-like pattern, whereas consistent patterns were not observed in the separate elevational transects. The bacterial community composition at the phylum level differed across the transects and elevation sites. The Actinobacteria was the most abundant phylum overall (41.76%) but showed clear variations in the different transects. Furthermore, heatmap analyses revealed that both pH and mean annual temperature (MAT) were significantly (P < 0.05) correlated with bacterial community composition as well as the dominant bacterial phyla, classes, and genera. These findings provide an inclusive view of bacterial community structures in relation to the environmental factors of the different elevational patterns.

Mimosa Origami: A nanostructure-enabled directional self-organization regime of materials.

One of the innate fundamentals of living systems is their ability to respond toward distinct stimuli by various self-organization behaviors. Despite extensive progress, the engineering of spontaneous motion in man-made inorganic materials still lacks the directionality and scale observed in nature. We report the directional self-organization of soft materials into three-dimensional geometries by the rapid propagation of a folding stimulus along a predetermined path. We engineer a unique Janus bilayer architecture with superior chemical and mechanical properties that enables the efficient transformation of surface energy into directional kinetic and elastic energies. This Janus bilayer can respond to pinpoint water stimuli by a rapid, several-centimeters-long self-assembly that is reminiscent of the Mimosa pudica's leaflet folding. The Janus bilayers also shuttle water at flow rates up to two orders of magnitude higher than traditional wicking-based devices, reaching velocities of 8 cm/s and flow rates of 4.7 µl/s. This self-organization regime enables the ease of fabricating curved, bent, and split flexible channels with lengths greater than 10 cm, demonstrating immense potential for microfluidics, biosensors, and water purification applications.

A 3D easily-assembled Micro-Cross for droplet generation.

We present an off-the-shelf device combined with some commercial adapters that performs as a micro droplet generator. The advantage of this unit lies in that it is assembled conveniently, connected elegantly with other droplet detection equipment, and it is high-pressure enduring. Most importantly, this Micro-Cross circumvents the problem of hydrophilicity and hydrophobicity and produces W/O or O/W droplets at a higher frequency than PDMS chips.