Directional liquid transport has been widely observed in various species including cacti, spiders, lizards, the pitcher plant Nepenthes alata , and Araucaria leaves. However, in all these examples the liquid transport for a specific liquid is completely restricted in a fixed direction. We demonstrate that Crassula muscosa shoot surfaces have the ability to transport a specific liquid unidirectionally in either direction. This is accomplished through the presence of asymmetric reentrant leaves with varying reentrant angles, which yields the variation in liquid meniscus heterogeneity. These findings enable engineered biomimetic structures capable of selective directional liquid transport, with functions such as intelligent flow direction switching, liquid distribution, and mixing.

Precision processing of various liquids while maintaining their purity holds immense potential for many applications. However, liquids tend to leave residues that contaminate handling tools and compromise volumetric precision, necessitating contactless strategies to prevent liquid loss. Biological and chemical samples carried by fluids can be sensitive to physical stimuli, demanding mild but effective means to preserve integrity. Here, we report a sound-controlled fluidic processor for complete and well-controlled microfluidic functions, including moving, merging, mixing, and cleaving, in contactless and harmless manners. The processor generates an acoustophoretic force field that serves as a versatile toolbox for manipulating droplets with surface tension from 17.9 to 72 millinewtons per meter and volume from 1 nanoliter to 3 milliliters, offering a wealth of operations crucial to fundamental biomedical and chemical practices.

Directed droplet manipulation is paramount in various applications, including chemical micro-reaction and biomedical analysis. The existing strategies include some kinds of gradients (structure, inherent wettability, and charge density), whereas they suffer from several limitations, such as low velocity, limited volume range, poor durability, and inefficient environmental suitability. Moreover, active bi-directional reversal of omni-droplets remains challenging because one kind of microstructure at a single scale cannot acquire two kinds of net results of mechanical interaction. Herein, we report an active and directional steering of omni-droplets utilizing bi-directional (vertical and horizontal) vibration on slippery cross-scale structures consisting of macro millimeter-scale circular arc arrays and micro/nanometer-scale slant ratchet arrays, which are fabricated by femtosecond laser patterned oblique etching and lubricant infusion. The physical mechanism of active droplet steering lies in the relative competition between the forces under vertical and horizontal vibration, which mainly arise from the circular arc arrays and slant ratchet arrays, respectively. Various steering modes, including climbing and programmable manipulation, can be realized. Our work is applicable to a wide range of potential applications, including circuit on/off and droplet-based chemical micro-reaction, particularly in the field of high-throughput omni-droplets operation.

Adjusting magnetization orienting and conformal assembling of high-coercivity micro-magnets at the microscale remains challenging, despite long-standing demand for space-resolved magnetic modulation in various applications. Local magnetic modulation, including remagnetization or reassembly, typically requires high fields and temperatures to overcome the coercivity and stringent conditions while suffering from low assembly efficiency or poor spatial resolution. Here, we report a linear magnet composed of a hydrogel (alginate) matrix and precisely discrete phase-change-material (PCM, eicosane) cells containing micro-magnetic particles (NdFeB, ~5 µm). Moderate local laser heating (~40 °C) reversibly switches PCM from solid to fluid state thus relaxing particles’ interfacial constraints inside the hydrogel matrix, overcoming the high-coercivity of magnetic assembly and allowing particles in cells to reorient under mild fields (≤30 mT). The linear magnet shows excellent discrete magnetization programmability (~150 µm) and stretchability (strain ~80%), enabling versatile functionalities such as conformal and patterned field generation, soft robotic actuation, flexible sensing, and interactive wearables with dynamically coded information.